DOT/FAA/AR-05/29 

Office of Aviation Research 

Washington, D.C. 20591

Inspection Development for 

Nickel Billet—Engine Titanium 

Consortium Phase II 

September 2005 

Final Report 

This document is available to the U.S. public 

through the National Technical Information Service (NTIS), 

Springfield, VA 22161. 

U.S. Department of Transportation 

Federal Aviation Administration
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Technical Report Documentation Page

1. Report No.

DOT/FAA/AR-05/29

2. Government Accession No. 3. Recipient's Catalog No.

5. Report Date 

September 2005 

 4. Title and Subtitle 

INSPECTION DEVELOPMENT FOR NICKEL BILLET—ENGINE 

TITANIUM CONSORTIUM PHASE II 6. Performing Organization Code

7. Author(s)

Mike Keller1, Thadd Patton1, Andrei Degtyar2, Jeff Umbach2, Waled Hassan3, 

Andy Kinney3

, Ron Roberts4, Frank Margetan4, and Lisa Brasche4

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

1

General Electric Company 

Cincinnati, Ohio 45215 

2

Pratt & Whitney 

East Hartford, CT

3

Honeywell Engines, Systems, & Services 

Phoenix, AZ 

4

Iowa State University 

Ames, IA

11. Contract or Grant No.

DTFA0398FIA029

13. Type of Report and Period Covered

Final Report

12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Aviation Administration 

Office of Aviation Research 

Washington, DC 20591 

14. Sponsoring Agency Code

ANE-110

15. Supplementary Notes

The FAA William J. Hughes Technical Center Technical Monitor was Cu Nguyen. 

16. Abstract

The Engine Titanium Consortium (ETC) is comprised of Iowa State University; General Electric; Pratt & Whitney; and 

Honeywell Engines, Systems & Services, and its objective was to develop improved inspection methods for critical jet engine 

components. The ETC Phase I program focused on improved inspection of titanium (Ti) billet using zoned inspection 

approaches. In the current work reported here, the multizone inspection procedure and transducers used for Ti were applied to 

typical nickel billet, namely Inconel 718 and Waspaloy. The program goal was achieved for 5′′ and 10′′diameter billet. 

17. Key Words 

Nickel billet, Ultrasonic inspection 

18. Distribution Statement 

This document is available to the public through the National 

Technical Information Service (NTIS), Springfield, Virginia 

22161. 

19. Security Classif. (of this report)

 Unclassified 

20. Security Classif. (of this page)

 Unclassified 

21. No. of Pages

 119 

22. Price

Form DOT F1700.7 (8-72) Reproduction of completed page authorized 
TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY ix 

1. INTRODUCTION 1-1 

1.1 Purpose 1-1 

1.2 Background 1-1 

1.3 Program Objectives 1-2 

2. APPROACH 2-1 

3. DISCUSSION OF RESULTS 3-1 

3.1 Initial Assessment 3-1 

3.2 Baseline Assessment 3-1 

3.2.1 Standards Fabrication 3-1 

3.2.2 Defining Conventional Ni Inspection 3-2 

3.2.3 Sensitivity Projections 3-4 

3.2.4 Transducer Characterization 3-6 

3.2.5 Standard Design and Fabrication 3-7 

3.2.6 Evaluation Results on the Calibration Standards 3-9 

3.2.7 IN718 Inspections 3-10 

3.2.8 Waspaloy Inspections 3-14 

3.2.9 Summary of Laboratory Evaluations 3-17 

3.3 Laboratory Demonstration 3-17 

3.4 Factory Pilot Lot Assessment 3-18 

3.5 Factory Demonstration 3-20 

3.6 Indication Characterization 3-21 

3.7 Summary of 10′′ Diameter Billet Assessment 3-23 

3.8 Small-Diameter Billet Study 3-24 

3.8.1 Inspection Setup and Results for Waspaloy 3-25 

3.8.2 Inspection Setup and Results for Ti-6Al-4V 3-32 

3.8.3 Comparison of the Three Inspection Methods 3-38 

4. SUMMARY 4-1 

5. REFERENCES 5-1 

iii
APPENDICES 

A—Defect Characterization of Naturally Occurring Anomalies 

 B—Data Acquisition Procedure 

 C—Nickel Small-Diameter Billet Data 

 D—Titanium Small-Diameter Billet Data

iv
LIST OF FIGURES 

Figure Page 

3-1 V-Die and GFM Billet C-Scans 3-4 

3-2 Waspaloy Billet C-Scans 3-6 

3-3 Three Measurement Geometries for Acquiring Data for Transducer 

Characterization 3-7 

3-4 Final Design of the Ni Billet Standards (IN718 Containing #1 and #2 FBHs and 

the Waspaloy Containing #2 and #3 FBHs) 3-8 

3-5 Two 10′′ Diameter Ni Billet Calibration Standards, IN718 and Waspaloy 3-9 

3-6 C-Scan of Conventional Inspection Zones 1 and 2 of an IN718 Calibration 

Standard 3-11 

3-7 C-Scans of Multizone Inspection Zones 1-6 of an IN718 Calibration Standard 3-12 

3-8 Comparison of Multizone Inspection Capability to IN718 10′′ Billet Program 

Goal and Laboratory Conventional Inspection Capability 3-13 

3-9 C-Scan of Conventional Inspection Zones 1 and 2 of a Waspaloy Calibration 

Standard 3-15 

3-10 C-Scan of Multizone Inspection Zones 1-6 of a Waspaloy Calibration Standard 3-16 

3-11 Comparison of Multizone Inspection Capability to Waspaloy 10′′ Billet Program 

Goal and Laboratory Conventional Immersion Inspection Capability 3-17 

3-12 Schematic of Indication Removal From Billet With Associated Orientation Labels 3-23 

3-13 The 5′′ Diameter ETC Billet Reference Standards (Waspaloy and Ti-6Al-4V) 

Containing #1 and #2 FBHs 3-25 

3-14 Single Transducer Inspection C-Scan of the 5′′ Diameter Waspaloy Billet 3-26 

3-15 Four Zones of Multizone Inspection C-Scans That Cover a Depth of 3′′ Into the 

Billet 3-28 

3-16 Layout of the 113 Elements on the Face of the 5-MHz Phased Array Transducer 3-30 

3-17 The Mechanical Setup Used in the Scanning of the Billet Standard 3-30 

3-18 Typical Results Collected During the Inspection for the #2 and #1 FBHs at a 

1.5′′ Depth 3-31 

v
3-19 Sixty-Inch Cylindrically Focused Transducer 3-33 

3-20 C-Scan of ST Inspection of the 5′′ Diameter Ti Billet 3-34 

3-21 C-Scans of the 5′′ Diameter Ti Billet Reference Standard 3-35 

3-22 Typical Results for the #2 and #1 FBHs at a 1.5′′ Depth 3-37 

3-23 Comparison of the SNR From the Three Techniques Used in Inspecting the 5′′

Diameter Waspaloy Billet Reference Standard 3-38 

3-24 Sensitivity vs Depth at SNR = 1.4 (3 dB) for the 5′′ Diameter Waspaloy Billet 

Reference Standard 3-39 

3-25 Comparison of the SNR From the Three Techniques Used in Inspecting the 5′′

Diameter Ti Billet Reference Standard 3-40 

3-26 Sensitivity vs Depth at SNR = 1.4 (3 dB) for the 5′′ Diameter Ti Billet Reference 

Standard 3-41 

vi
LIST OF TABLES 

Table Page 

3-1 Summary of OEM Processes for Conventional Ni Billet Inspection 3-3 

3-2 Mean Noise Levels Normalized to Calibration Plus 30 dB for the Three Alloys 3-5 

3-3 Calibration and Noise Statistics for #1 FBH Sensitivity on IN718 Standard 3-19 

3-4 Multizone vs Conventional—Investment, Maintenance, Labor, and Operating 

Cost Comparisons 3-21 

3-5 List of Indications and the Amplitudes Relative to #1 and #2 FBH Calibrations 3-22 

3-6 The EDAC for Waspaloy Conventional and ST Inspections 3-25 

3-7 Signal-to-Noise Ratio for Conventional and ST Inspections of 5′′ Diameter 

Waspaloy Billet Reference Standard 3-27 

3-8 Multizone Production Transducers 3-28 

3-9 Signal-to-Noise Ratio for Multizone Inspection of 5′′ Diameter Waspaloy Billet 

Reference Standard 3-29 

3-10 Phased Array Inspection Parameters for the Waspaloy 5′′ Diameter Billet 

Standard 3-31 

3-11 Signal-to-Noise Ratio Results Collected During the Phased Array Inspection of 

the 5′′ Diameter Waspaloy Reference Billet Standard 3-32 

3-12 Electronic Distance-Amplitude Correction for Ti-6Al-4V Conventional and ST 

Inspections 3-33 

3-13 Signal-to-Noise Ratio for Conventional and ST Inspections of 5′′ Diameter Ti 

Billet Reference Standard 3-34 

3-14 Signal-to-Noise Ratio for Multizone Inspection of a 5′′ Diameter Ti Billet 

Reference Standard 3-35 

3-15 Phased Array Inspection Parameters for the 5′′ Diameter Ti Billet Standard 3-36 

3-16 Signal-to-Noise Ratio Results Collected During the Phased Array Inspection of 

the 5′′ Diameter Ti-6Al-4V Reference Billet Standard 3-37 

vii
LIST OF ACRONYMS 

AMS Aerospace Material Specification 

ASTM American Society for Testing and Materials 

DAC Distance-amplitude correction 

dB Decibel 

EDAC Electronic distance-amplitude correction 

ETC Engine Titanium Consortium 

FAA Federal Aviation Administration 

FBH Flat-bottom hole 

FSH Full-screen height 

GE General Electric 

GE-QTC General Electric Quality Technology Center 

GFM Gesellschaft fur Maschinenbau-und-fertigungstechnik 

IN718 Inconel 

ISU Iowa State University 

Ni Nickel 

OEM Original equipment manufacturer 

P&W Pratt & Whitney 

PoD Probability of detection 

SNR Signal-to-noise ratio 

ST Single transducer 

Ti Titanium 

viii
EXECUTIVE SUMMARY

The Engine Titanium Consortium (ETC) Phase I production inspection efforts focused on 

titanium (Ti) billet using zoned inspection procedures. The Phase II program applied the 

multizone procedures and transducers originally developed for Ti to nickel (Ni) billet. The 

program included design of calibration standards, laboratory assessment and demonstration, and 

factory assessment and demonstration for 10′′ diameter billet. A comparison of multizone and 

phased array inspection to conventional inspection was also completed for 5′′ diameter billet. 

• Billet converted with Gesellschaft fur Maschinenbau-und-fertigungstechnick (GFM) 

processing is more acoustically noisy than billet converted using V-Die processing. 

GFM material was selected for use in calibration standards since this provides a more 

conservative assessment. 

• Transducer characterization procedures were developed for bicylindrically focused 

transducers, which are useful for ensuring that actual focal characteristics match the 

intended design values. 

• The Waspaloy calibration standard was more ultrasonically noisy than the Inconel 718 

(IN718) material (75% peak noise compared to 20%, respectively) when measured with 

the same calibration target. 

• The multizone inspection procedure and transducers originally used for Ti successfully 

exceeded the program goal of #1 flat-bottom hole (FBH) for IN718 and #2.5 FBH for 

Waspaloy by substantial margins. The multizone system exceeded the IN718 goal by a 

minimum of 3.5 times and was a minimum of 31 times more sensitive than the current 

conventional inspection requirement. Multizone exceeded the Waspaloy goal by a 

minimum of 4 times and was a minimum of 14 times more sensitive than the current 

conventional inspection requirement. 

• The use of conventional transducers in two-zone laboratory inspection nearly met the 

program goal for IN718. The laboratory conventional immersion inspection exceeded the 

program goal of #2.5 FBH sensitivity for Waspaloy in the near-surface zones. No data 

was gathered for the production conventional contact inspection of Waspaloy. 

• The factory assessment showed that the surface finish used for conventional inspection 

was adequate for the increased sensitivity of the multizone test, although the multizone 

test is more sensitive to surface blemishes. 

• The factory assessment showed comparable characteristics for inspection of Ni when 

compared to experience with inspection of Ti multizone procedures. 

• A cost comparison revealed increased investment and operational cost for multizone 

compared to conventional. Increased operational costs associated with multizone 

inspections were documented for setup, scanning, and analysis. 

ix
• Suppliers expressed concerns regarding transducer manufacturability and limited 

availability of transducer vendors. 

• The factory demo on 81,000 pounds of two and three times melted IN718 generated 

conclusive results that the multizone system can detect indications that are missed by the 

current conventional inspection. A total of 19 indications were detected by multizone, all 

of which were significantly smaller than conventional inspection requirements that are at 

a #2 FBH sensitivity and, therefore, below the threshold for detection. 

• Conventional inspection of 5′′ diameter billet nearly met the current #2 FBH sensitivity in 

the center zone of both Ti and Waspaloy standards. However, slight modification of the 

current conventional inspection to reflect the method used for evaluating the results from 

the single transducer inspection show that a significant improvement if the sensitivity 

could be achieved. 

• Multizone and phased array inspections of 5′′ diameter Waspaloy billet indicated that 

multizone achieved about a #0.5 FBH sensitivity throughout most of the billet depth 

while phased array achieved about a #0.75 FBH. The multizone inspection exceeded the 

conventional inspection sensitivity by about 20 times at the billet center. 

• Multizone and phased array inspections of 5′′ diameter Ti-6Al-4V billet indicated that 

both achieved about a #0.75 FBH sensitivity throughout the billet depth, which exceeded 

the conventional immersion sensitivity by about nine times. 

x
1. INTRODUCTION. 

1.1 PURPOSE. 

The purpose of this program was to develop higher-sensitivity inspection methods for nickel (Ni) 

billets that could be used to reduce the occurrence of melt-related defects in Ni forgings and, 

therefore, lower the engine failure risk. Two Ni alloys commonly used among the engine 

manufactures are Inconel 718 (IN718) and Waspaloy. Both represent a significant percentage of 

Ni disks in use by the industry. These alloys also present different challenges for ultrasonic 

inspection due to microstructure differences between the two and were selected for evaluation in 

this effort. 

1.2 BACKGROUND. 

Typical billet diameters of 8′′, 10′′, 12′′, and 14′′, which are currently inspected to a sensitivity of 

#2 flat-bottom hole (FBH) and larger are used for large engines that power commercial 

transports. A single, spherically focused, 5-MHz transducer is generally used to achieve the 

required sensitivity. Current inspection of Ni alloys is limited by material grain noise, with 

typical grain sizes of 11 to 90 μm (American Society for Testing and Materials (ASTM) 10 to 4) 

for IN718 and primarily 60 to 90 μm in Waspaloy. A program goal of four times improvement 

over the current conventional inspection method was established. The technical approach of this 

program was to reduce the impact of grain noise on the inspection capability by using multiple, 

bicylindrically focused multizone transducers. Alloy selection for jet engine applications is 

based on the operational requirements with factors such as stress, temperature, environmental 

conditions, and weight being considered. Ni alloys are selected for use at areas of high 

operational temperatures (800° to 1500°F), such as the compressor and turbine stages of the 

engine. Given the consequences of failure, there is a need for sensitive and effective inspection 

methods. A four times improvement in sensitivity would be achieved if the #2 FBH sensitivity 

of the current IN718 billet inspection were improved to a #1 FBH sensitivity. Waspaloy billets 

of 8′′ to 14′′ are currently inspected to a #5 FBH sensitivity, so a four times improvement would 

be achieved with a #2.5 FBH sensitivity inspection. 

Considerable effort has gone into the development of focused zoned inspection. The method 

commonly referred to as multizone [1, 2, 3, 4, and 5] was initially developed by General 

Electric (GE) with subsequent improvement as part of the Engine Titanium Consortium (ETC) 

Phase I and Phase II programs. The ETC is a university/industry partnership comprised of Iowa 

State University (ISU); GE; Pratt & Whitney (P&W); and Honeywell Engines, Systems & 

Services. The ETC approach includes the measurement and utilization of materials properties 

information relevant to ultrasonic inspectability [6, 7, 8, 9, 10, and 11]. Properties including 

ultrasonic velocity, attenuation [12], and backscatter noise [, 13, 14, 15, 16, and 17] were 

correlated to microstructural and macrostructural conditions of representative alloy samples [18]. 

The Phase I program focused on improvements to inspection of titanium (Ti) billet [19]. 

Two approaches to zoned inspection of Ti billet were evaluated in the ETC Phase I program: 

multizone [20] and phased array [21]. In comparative studies performed as part of the 

contaminated billet study, both methods detected the same indications, although with variation in 

amplitude and signal-to-noise ratio (SNR). Given the success of the multizone method for 

1-1
improved sensitivity inspection of Ti billet and the existence of several commercial inspections, 

the ETC Phase II program was aimed at extending this method to Ni billet. 

Sound velocities for the Ni alloys (IN718 and Waspaloy) are only about 2% slower than the 

sound velocities of the Ti alloys used in ETC Phase I. It was postulated that the fixed-focus 

transducers used for multizone inspections in ETC Phase I would also be applicable to these Ni 

alloys in a straightforward manner. The ETC Phase II program generated fundamental property 

data [22] for IN718 and Waspaloy and applied the multizone inspection method to Ni billet. 

This report provides details of the latter. 

1.3 PROGRAM OBJECTIVES. 

• To apply technology developed in ETC Phase I for Ti billet inspection to improve Ni 

billet inspection. 

• To perform factory inspection of approximately 100,000 pounds of Ni alloy billet, 

primarily IN718, to a #1 FBH sensitivity using a multizone inspection system with digital 

acquisition to provide necessary field experience that facilitates implementation 

decisions. 

• To determine applicability of the multizone technique to Waspaloy. 

• To provide the billet industry and original equipment manufacturers (OEM) with a 

demonstration of improved sensitivity inspection using FBH standards as the metric, with 

a goal of #1 FBH sensitivity in 10′′ diameter IN718 billets and #2.5 FBH sensitivity in 

10′′ diameter Waspaloy billet. 

• To provide necessary data to the Inspection Systems Capability team for estimation of 

probability of detection (PoD) for Ni billet, including cutup data generated in the pilot lot 

inspection. 

1-2
2. APPROACH. 

The approach used for this research program included the following: 

• Initial Assessment: Activities included selection of representative alloys, design and 

manufacture of calibration standards, and identification of target sensitivity and SNR 

criteria. 

• Baseline Assessment: Initial effort included definition of conventional Ni billet 

inspection, development of sensitivity curves for that conventional inspection, as well as 

for sensitivity curves for multizone using transducers originally designed for Ti billet. 

• Laboratory Demonstration: Using calibration standards fabricated from 10′′ diameter 

IN718 and Waspaloy billets, a laboratory demonstration was held with attendees from the 

billet and forging supplier community. 

• Small Diameter Billet Assessment: A study specific to smaller diameter (5′′) billet was 

carried out using both Ni and Ti calibration standards. The study compared conventional, 

multizone, and phased array inspection methods. 

• Factory Demonstration: Upon completion of the laboratory demonstration, arrangements 

were made for a factory inspection of 50,000 pounds of triple-melt IN718, 25,000 pounds 

of double-melt IN718, and 25,000 pounds of Waspaloy. Because of industry production 

rates, the actual inspection was limited to IN718. The product evaluated in the factory 

was limited to 10′′ diameter. Near the completion of the inspection pilot run, a factory 

demonstration was held with the billet supplier community. 

2-1/2-2
3. DISCUSSION OF RESULTS. 

3.1 INITIAL ASSESSMENT. 

A kickoff meeting involving the ETC team members was held in June 1999 to reiterate the plans 

of the task and established a means of sharing information and data, including coordination of 

efforts with other tasks underway in the ETC Phase II program. This included coordination with 

reliability efforts. IN718 and Waspaloy were selected as the alloys to be studied in the program 

with target sensitivities of #1 and #2.5 FBHs, respectively. Requirements for signal-to-noise 

measurements were also established. The number and types of calibration standards were 

discussed, and design of the standards initiated. Production calibration standards for 10′′

diameter IN718 and Waspaloy were agreed upon in the initial planning meeting and 

subsequently manufactured. 

3.2 BASELINE ASSESSMENT. 

An evaluation of the current capability of conventional inspections was performed as a baseline 

for both IN718 and Waspaloy using the production calibration standards rather than relying on 

nominal values stated in the respective specifications. Inspection development was performed 

with the calibration standards using existing production multizone transducers. These 

evaluations took place principally at the GE facilities with P&W personnel in attendance to 

facilitate hands-on involvement by the parties responsible for final implementation 

recommendations. Scans and associated measurements were used to determine the focal depth 

of each transducer, measure the axial beam profile and beam cross section, and compare these 

results to model predictions. SNRs were determined for the FBH targets and sensitivity curves 

were generated. Following evaluation of the existing production transducers, it was determined 

that redesigned transducers would not be necessary to meet the stated goals. The conventional 

inspection sensitivity was established based on production inspection criteria after a review of all 

three OEM’s production inspection procedures. 

3.2.1 Standards Fabrication. 

The Fundamental Studies [22] effort of the ETC program was charged with studying and making 

recommendations to the Ni billet inspection development task regarding material sectioning for 

standards fabrication. Team members worked closely with the fundamental studies group in the 

initial stages of the program to select the material and establish the process for inspection 

development. Many of the decisions regarding alloy selection and billet diameters were agreed 

upon at the initial kickoff meeting and were based on industry needs. At that time it was decided 

that IN718 alloy was widely used by all three OEMs, Waspaloy is used by two of the three, and 

that 10′′ diameter billet fit the requirements for larger engines. The inspection development 

effort focused on 10′′ diameter IN718 and Waspaloy. A separate study for smaller diameter 

billet was also planned. 

Experience indicates that acoustic properties and the resultant inspection sensitivities are often 

dependent on the way the material is processed. If these properties are significantly different, it 

is good practice to make a standard representing each process even though the alloy’s chemical 

composition is the same. Because IN718 is ordered by the OEMs either using double 

3-1
(VIM/VAR) or triple melt (VIM/ESR/VAR), or depending on the supplier, different conversion 

practices, further refinement of the material selection process was required. All Waspaloy used 

by the OEMs was double (VIM/VAR) melted so no material selection was necessary. 

A survey of several IN718 inspection facilities reported only minor differences in acoustic noise 

between the double- and triple-melt product, and as a consequence, there was no further 

consideration in making a standard of each. The more significant difference would lie in the 

conversion process. Currently, there are two conversion practices commonly used to convert the 

cast 718 ingot into finished cylindrical billets, referred to as the Gesellschaft fur Maschinenbauund-fertigungstechnik (GFM) and V-Die processes []. With direction from the fundamental 

studies effort, a 30-inch section of each type of IN718 was procured for study. An ultrasonic 

evaluation of these two 30-inch-long samples indicated the GFM-processed billet produced, on 

average, more acoustic noise than the V-Die material.

One standard of the noisiest (GFM converted) IN718 billet material was selected. It was 

reasoned that a standard made from the process that is presumably the more difficult to inspect 

would lead to a more conservative result. It was also postulated that if multizone evaluation 

takes place under the more difficult conditions, it is likely to work for the less noisy billet as 

well. For this reason, the GFM billet was chosen for fabrication of the standard. An order was 

placed for the GFM-produced billet according to the normal purchase specification for rotorgrade material. The grain size requirement for the billets was ASTM 5 or finer with less than 

20% being ASTM 2 to be consistent with specifications for production material of 8′′ diameter or 

greater. 

A second survey of suppliers of Waspaloy material led to the selection of GFM-processed 

material because it is widely used for Waspaloy conversion. The final IN718 standard was 10′′

diameter, triple-melt GFM-converted material. The final Waspaloy standard was also 10′′

diameter, double-melt GFM-converted material. Detailed information on the evaluations leading 

to this decision is presented in a companion report of the ETC fundamental studies effort []. 

3.2.2 Defining Conventional Ni Inspection. 

To measure sensitivity improvement in the multizone inspection technique applied to Ni billet, 

the baseline conventional inspection sensitivities were needed to be defined. Each of the OEMs 

was asked to provide details on their conventional Ni billet inspection processes, which are 

summarized in table 3-1. 

Comparison of the three processes used by the OEMs to inspect IN718 revealed a number of 

similarities, such as static calibration, zoned inspection permitted, 5-MHz transducers, normal 

incidence, and no strip charts or C-scans. However, some differences were noted in the FBH 

size used in the calibration standard that ranged from #2 to #3 FBH and reject levels that 

included 50% of #2 FBH or 100% of #3 FBH. Evaluation of the different techniques resulted in 

selecting process 1 as a representative baseline for IN718 and process 4 for Waspaloy billet 

inspection. In summary, the IN718 baseline conventional inspection was to a #3 FBH sensitivity 

and Waspaloy was to a #5 FBH sensitivity. 

3-2
TABLE 3-1. SUMMARY OF OEM PROCESSES FOR CONVENTIONAL 

Ni BILLET INSPECTION 

IN718 Waspaloy 

Calibration Standard Process 1 Process 2 Process 3 Process 4 Process 5 

Alloy/Grade VIM/VAR VIM/ESR/VAR VIM/ESR/VAR N/A Type 1/Type II 

VIM/VAR/ 

VIM/ESR 

Is one std. used for all grades? Yes Yes Yes 2x N/A Yes 

Referenced to master standard? No No No No 

Dynamic or Static Static Static Static Static Static 

FBH size #3 #3 #2 #5 #8 

FBH depths 0.25′′-5′′ Note 1 0.25′′, 0.75′′, 1.25′′, 

2.5′′, 5.5′′

0.25′′-5′′ Note 1 

Inspection Transducers Note 2 

For each zone if applicable Zone 1/Zone 2 

Element size 0.75′′ 0.75′′ dia / 0.75x1.0′′ 0.75′′

Focal length 

Frequency 5 MHz 5 MHz/5 MHz 5′′

Beam size (approximately) 0.112′′

3 dB depth of field 0.9′′

Calibration Procedure 

Zone inspect? Allowed Note 3 Yes Allowed Note 3 

Zone 1 focus/DAC Subsurface/yes 

Zone 2 focus/DAC 2′′ subsurface/yes 

Zone 3 focus/DAC N/A 

Reporting Requirements 

80% FSH = 100% 80% FSH = 100% 80% FSH = 100% 

Sensitivity Level 

(% of calibration) 

#3 FBH #2 FBH N/A #8 FBH 

Alarm threshold/evaluation level 50% (Note 5) 50% 25% 50% (Note 5) 50% 

Maximum-allowable noise level 50% 25% N/A 50% 

Reject level 100% 100% 50% 100% 100% 

Inspection Parameters 

Angle of incidence Normal Normal Normal Normal Normal 

Pulse on position? No No N/ A No 

Rotation speed (>500 PRF) Note 4 13′′/sec. surface (>500 PRF) Note 4 

Scan index <1/2 EBW <80% EBD 0.070′′ <1/2 EBW <80% EBW 

Translational speed N/A Note 4 N/A N/A Note 4 

Strip chart/C-scan No No No No No 

EBD-Effective beam diameter PRF-Pulse repetition frequency 

EBW-Effective beam width N/A-Not available 

Notes: 

1. FBH depths as required for establishing distance-amplitude correction (DAC). Surface resolution shall be as 

agreed upon with an OEM-approved inspection procedure. 

2. Transducers shall be capable of providing sufficient resolution and sensitivity to detect the applicable reference 

reflector. 

3. When near-surface resolution and depth of penetration cannot be accomplished in a single scan, multiple scans 

shall be performed in a series of smaller metal travel tolerance using ASTM reference. 

4. Scanning speed shall not exceed the maximum speed that provides for detection of all discontinuities in the part. 

5. Value stated is not the required value but is a likely value that is used. 

3-3
3.2.3 Sensitivity Projections. 

Much of the research involved in the fundamental studies effort was conducted simultaneously 

and in cooperation with the production inspection development effort. With this in mind, the 

sections of material ordered for the fundamental studies measurements were specified to a length 

taking into account that the same material might be fabricated into standards. Once the material 

arrived, an initial evaluation was conducted at the GE laboratory facility using the multizone 

inspection procedure currently used for Ti. The instrumentation sensitivity level was calibrated 

using the GE Ti billet standard containing #2 FBHs. Each IN718 billet was then scanned with 

increased sensitivity so that the mean material noise was kept between 20% and 60% full-screen 

height (FSH) amplitude. This increased sensitivity over calibration was recorded in decibels 

(dB) for each of the six zones of the multizone inspection. Peak noise levels observed in the 

C-scans were kept below saturation. The results for the six zones are shown in figure 3-1. This 

includes both V-Die- and GFM-processed IN718 10′′ diameter billet. 

IN718 V-Die IN718 GFM

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

Backwall

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

Backwall

FIGURE 3-1. V-DIE AND GFM BILLET C-SCANS 

3-4
Table 3-2 shows the normalized mean noise values, comparing the V-Die and GFM billets for 

IN718. These preliminary inspections at the arbitrary gain settings provided an initial look at the 

expected inspection capability for this material as well as identifying possible unacceptable 

inclusions or conditions that might render the material unacceptable for standard use. 

TABLE 3-2. MEAN NOISE LEVELS NORMALIZED TO CALIBRATION 

PLUS 30 dB FOR THE THREE ALLOYS 

Average Material Noise at Ti #2 + 30 dB 

IN718 Waspaloy 

Zone D-Die GFM GFM 

2 

3 

4 

5 

6 

23 

25 

30 

44 

39 

34 

32 

37 

55 

50 

79 

101 

104 

136 

108 

In estimating the potential inspection capability, the gain setting relative to the #2 Ti calibration 

level is compared to the peak noise level in the material under investigation. By comparing the 

acoustic impedance between Ti and IN718, a correction can be made for the energy transfer 

differential at the water-to-material interface. In the case of Ti versus IN718, the acoustic 

impedance is about 1.8 or 5.5 dB. Therefore, it will take about 5.5 dB additional gain to achieve 

the equivalent sound field in IN718 as for Ti. Using the area amplitude relationship between a 

#2 FBH and a #1 FBH, the sensitivity is about 4 times greater or 12 dB. Adding the 5.5 dB 

insertion loss to the 12 dB sensitivity, the resultant sensitivity to a #1 FBH is 17.5 dB. Since the 

prescans were conducted at plus 30 dB, this meant that the IN718 billet was inspected at a 

projected #1 FBH plus about 12 dB. Lowering the mean and peak noise values for each of the 

C-scan zones by 12 dB suggested that the goal of achieving #1 FBH sensitivity with a SNR of 

3 dB or greater was highly probable. Having this much margin in sensitivity made it unlikely 

that new transducers would have to be designed, specifically for Ni. The more subtle differences 

in velocity and attenuation that will affect the transducer focus might well be ignored, allowing 

use of existing transducers originally designed for Ti. 

The same analysis was conducted using the Waspaloy material. Figure 3-2 provides the C-scan 

results. Here again the prospects of achieving the goal of #2.5 FBH looked well within reach. 

Of course, one could not be certain of the final sensitivity until the FBHs were placed in the 

standard and the transducers calibrated on these targets. The noise values normalized to Ti #2 

FBH level +30 dB for the Waspaloy billet are included in table 3-2. 

3-5
Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

Backwall

Waspaloy GFM

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

Backwall

Waspaloy GFM

FIGURE 3-2. WASPALOY BILLET C-SCANS 

3.2.4 Transducer Characterization. 

Multizone transducers used for billet inspections are bicylindrically focused to compensate for 

the curved sound-entry surface of the billet. There are two distinct focal zones in water, but 

these coalesce to a single focal zone in the metal after transmission through the billet surface. 

The sharp focusing of the beam in the metal tends to improve SNRs for small internal defects. 

The focal characteristics claimed by transducer manufacturers are sometimes inaccurate. Thus, 

prior to certifying transducers for service, it is useful to determine how accurately actual focal 

characteristics match the intended design values. Such determinations are referred to as 

transducer characterization. 

3-6
Investigators at ISU developed generic software to characterize multizone transducers using the 

IN718 10′′ billet calibration standard. The software characterizes a transducer’s projected beam 

pattern by measuring a quantity called the V(z) profile [23]. This software is beneficial in 

predicting the response and performance of transducers from known targets. 

ISU developed three approaches for characterizing multizone transducers. The measurement 

geometry for each method is shown in figure 3-3. The three methods were then used to 

characterize a typical 5-MHz multizone transducer, namely one designed to focus 3.15′′ deep 

(zone 4) in 10′′ diameter Ti alloy billet. Details of the work are included in the companion ETC 

report for Ti billet [24]. It was recommended, on the combined basis of ease of use and overall 

accuracy, that the V(z) method be used by OEMs interested in performing their own transducer 

characterizations. The V(z) measurements consist of capturing digitized front-wall radio 

frequency (RF) echoes at normal incidence from a flat reflector in water. Data is gathered at 

100-200 equally spaced water paths, which bracket the two principal focal zones. A userfriendly version of the V(z) probe characterization software was developed for use by the OEMs, 

and a companion user’s manual was written. The results are also described in this report and 

several publications [23]. 

Beam Mapping in Water Beam Mapping in Solid V(z) Method

FBH

scan

scan

scan

Hemispherical

target

2D scan over target

at each of several

water paths.

No special specimen

needed. Get direct

info about beam

widths, but beam

profiles are

somewhat complex.

2D scan over target

for each of several

FBH depths.

Special specimen

needed. Get direct

info about beam

widths in the actual

billet geometry.

1D scan over flat

surface (typically >

100 water paths)

Simplest experiment.

No direct information

about beam widths in

the two lateral

directions, but probe

char.’s can be inferred.

(a) (b) (c)

FIGURE 3-3. THREE MEASUREMENT GEOMETRIES FOR ACQUIRING DATA FOR 

TRANSDUCER CHARACTERIZATION 

3.2.5 Standard Design and Fabrication. 

Foremost to most ultrasonic inspection development is the design and fabrication of a standard 

containing a series of reflecting targets from which the sensitivity of the inspection is calibrated. 

The physical characteristics of the Ni standards were for the most part modeled after the design 

3-7
provided in the SAE International Aerospace Material Specification (AMS) 2628 specification 

for Ti billet. These standard designs make provision for dynamic as well as the traditional static 

calibration. A dynamic-designed standard is one that will allow more complete testing of the 

whole inspection system and simulates actual inspection speed and motion. It also allows the 

creation of a C-scan image of the standard, useful in collecting noise statistics. The calibration 

standard design includes a solid section of material that provides an opportunity to evaluate 

attenuation characteristics and can aid in transducer normalization. A significant departure from 

the AMS design was the addition of an extra hole placed at a depth between the two extreme 

holes for each zone. This additional hole is useful in measuring beam profiles and determining 

scanning indexes for production inspection. 

A second complete set of calibration holes were also planned for the standard. The goal was to 

achieve a #1 FBH sensitivity for IN718 to be compared with a #3 FBH sensitivity for 

conventional inspection. The team decided that instead of #3 FBHs being placed in the standard, 

#2 FBHs would be machined. There is significant evidence from the GE conventional inspection 

that #2 FBHs would be relatively easy to identify and that corrections could be made to 

inspection sensitivity at the #3 FBH level. Therefore, both #1 and #2 FBHs were placed in the 

standard to provide an opportunity to evaluate conventional inspection transducers as well. 

Figure 3-4 shows the final design of the standard. 

FIGURE 3-4. FINAL DESIGN OF THE Ni BILLET STANDARDS (IN718 CONTAINING #1 

AND #2 FBHs AND THE WASPALOY CONTAINING #2 AND #3 FBHs) 

Current hole drilling for the #1 FBHs in the IN718 standard is less than 1/2 inch deep. These 

small diameter holes required the drilling of a pilot hole 1/4 of an inch deep, then the #1 FBH 

3-8
was drilled an additional 1/4 inch, making a total hole depth of 1/2 inch. This needs to be 

considered during calibration so as not to mistake the shoulder of the pilot hole for the FBH 

response. 

The Waspaloy standard was designed in the same manner as the IN718 standard with the 

exception that both #2 and #3 FBHs were drilled. The Waspaloy inspection goal was a #2.5 

FBH. Here, the #2 and #3 FBHs framed the target size. The target hole can be mathematically 

calculated from the responses of the actual targets based on the area amplitude relationship. 

Spacing between target holes was generous to permit evaluation of conventional transducer 

beams. 

3.2.6 Evaluation Results on the Calibration Standards. 

Once the calibration standards for IN718 and Waspaloy were machined, both of the 10′′ diameter 

standards were evaluated at the GE Quality Technology Center (QTC) billet inspection facility. 

Figure 3-5 shows two 500-lb, 10′′ diameter standards. 

FIGURE 3-5. TWO 10′′ DIAMETER Ni BILLET CALIBRATION STANDARDS, 

IN718 AND WASPALOY 

Multizone inspections were conducted using the same 5-MHz transducers specified for 

production inspections of 10′′ Ti billet material. Conventional inspections were conducted using 

similar transducers to those used by production billet suppliers. 

3-9
3.2.7 IN718 Inspections. 

A conventional inspection was conducted for IN718 in the GE-QTC laboratory tank using the 

test parameters identified below: 

• Instrument: KB6000 (S/N 311269, pulser model 311526, receiver model 311316) 

• Zone 1 transducer: Harisonic I7, 5 MHz, spherical focus, 0.75-inch element diameter, 

6-inch focal length operated at a 6-inch water path 

• Zone 2 transducer: KB Gamma, 5 MHz, 0.75- x 1.0-inch rectangular element, 7-inch 

cylindrical focus operated at a 5- and 2-inch water path 

The two-zone inspection was conducted using DAC. The zone 1 transducer covered depths from 

0.2′′ to 2.25′′. It has a 6′′ focal length, and a 6′′ water path was employed so the beam was 

focused very near the billet surface. The zone 2 transducer covered depths from 1.8′′ to 5.5′′. 

The laboratory inspection was conducted using a 5′′ water path. A second inspection using a 

shorter (2′′) experimental water path was also completed to evaluate the effect of moving the 

zone 2 focal point deeper into the billet. The standards were inspected by calibrating both 

transducers on the shallowest #2 FBH and adjusting the gain and DAC until all FBHs reached an 

amplitude of 80% FSH. To avoid reflections from the circumferentially machined surfaces, the 

nonproductive technique of gating each hole just short of these surfaces was used. This 

technique permitted clearer C-scans of all holes. 

The simulated two-zone production inspection, using a #2 FBH calibration and a 5′′ water path 

for the conventional two-zone transducers, produced the C-scans shown in figure 3-6. The zone 

1 transducer C-scan indicates all the #2 and #1 FBHs can be identified. The zone 2 transducer 

C-scan easily identifies all the #2 FBHs, but the #1 FBHs are more below the threshold and 

cannot be distinguished from the background noises at depths greater than about 2.7′′. 

The multizone inspection was also conducted at GE-QTC in the laboratory tank using 

transducers manufactured to the same specification as production transducers. The same 

transducers specified for Ti billet inspections were used for inspecting the Ni standards. There 

are a total of six zones, each covering approximately 0.9′′ of the billet. Details of the instrument 

and transducers are provided below: 

• Instrument: P/N 94ASY020G, S/N 002 

• Pulser preamp: P/N 91ASY028G, S/N 013 

• Zone 1: NDT systems, P/N AE08402GE, S/N 124151, focus 0.4′′ deep 

• Zone 2: NDT systems, P/N AE08418GE, S/N 02554, focus 1.3′′ deep 

• Zone 3: NDT systems, P/N AE08420GE, S/N 035120, focus 2.2′′ deep 

• Zone 4: NDT systems, P/N AE08422GE, S/N 035127, focus 3.1′′ deep 

• Zone 5: NDT systems, P/N AE08424GE, S/N 035221, focus 4′′ deep 

• Zone 6: NDT systems, P/N AE08426GE, S/N 04544, focus 5′′ deep 

3-10
FIGURE 3-6. C-SCAN OF CONVENTIONAL INSPECTION ZONES 1 AND 2 OF AN 

IN718 CALIBRATION STANDARD 

Prior to final sensitivity adjustment, the water path of the transducer for each zone was adjusted 

to produce the best balance in response from the near and far holes for each zone. Instrument 

sensitivity was then calibrated using #1 FBHs, with the individual gain levels adjusted to 

produce 80% FSH amplitude for the least reflective of the three FBHs in each zone. The C-scans 

for each zone are shown in figure 3-7. Note that all the #2 and #1 FBHs can be readily detected 

in all inspection zones. 

3-11
Zone 1 

0.2-0.55-0.9 

Zone 3 

1.8-2.25-2.7 

Zone 2 

0.9-1.35-1.8 

#2 

#1 

Zone 4 

2.7-3.15-3.6 

Zone 5 

3.6-4.05-4.5 

Zone 6 

4.5-5.0-5.5 

#2 

#1 

FIGURE 3-7. C-SCANS OF MULTIZONE INSPECTION ZONES 1-6 OF AN 

IN718 CALIBRATION STANDARD 

• Comparison to Program Goal. 

The program goal was to demonstrate that the multizone inspection, using the 5-MHz 

transducers developed for 10′′ Ti billet, were capable of inspecting IN718 rotor-grade 

billet to a #1 FBH sensitivity from the surface to the center of the billet. If achieved, this 

would represent a nine times improvement over the production conventional inspection 

as defined in the program. 

3-12
To determine whether the program goal has been attained, an SNR must be defined 

which permits detection of the FBH at an acceptable false call rate and provides a 

standard means of comparing conventional and multizone inspection procedures. The 

multizone Ti billet inspection specification used in production has identified an SNR of 

2.5 as providing an acceptable level of detectability combined with a reasonable false call 

rate as established from field evaluations. However, because many conventional 

inspections use an SNR much less than 2, a 3 dB or 1.4125:1 was adopted for evaluation 

of inspection sensitivities. The multizone and laboratory conventional data were plotted 

against the program goal of #1 FBH in figure 3-8 in terms of FBH#. The FBH sensitivity 

plotted on the y axis is defined as: 

Sensitivity in FBH# = FBH #cal 80/)]4125.1)([( npk S

Where FBH#cal = Flat bottom hole number used for calibration 

 Snpk = Peak noise amplitude 

FIGURE 3-8. COMPARISON OF MULTIZONE INSPECTION CAPABILITY TO 

IN718 10′′ BILLET PROGRAM GOAL AND LABORATORY CONVENTIONAL 

INSPECTION CAPABILITY 

This sensitivity definition requires that the calibration target in the fully gated inspection 

zone be 3 dB higher than the peak noise and the calibration level be 80% FSH. These 

normalized FBH numbers are plotted for each zone in figure 3-8. 

The multizone inspection sensitivity, after being normalized to an SNR of 3 dB, exceeded 

the program goal of #1 FBH at all depths in the billet. At the billet center, it is 

approximately 31 times more sensitive than the current conventional production 

inspection and about 3.5 times better than the program goal. These values were very 

3-13
close to earlier predictions about the achievable sensitivity based on the initial material 

inspection of +30 dB. The laboratory conventional data (zone 2 at 5′′ and 2′′ water paths) 

are also plotted in figure 3-8. Although SNR is not normally measured on conventional 

inspections, the SNR was determined using the normalized sensitivity at SNR = 1.4125. 

The laboratory conventional inspection was approximately equal to the program goal for 

zone 1 and slightly less (FBH# 1.188 - 5′′ water path) for zone 2. 

3.2.8 Waspaloy Inspections. 

Evaluation of the 10′′ diameter Waspaloy calibration billet was completed using the same 

procedures as applied to the IN718 billet. The calibration billet was machined to the same 

configuration (see figure 3-4). The only difference was the size of the FBH calibration holes—

the Waspaloy standard contained #2 and #3 FBHs at each of the inspection depths. 

The conventional inspection used by suppliers on 10′′ billet used contact transducers calibrated to 

a #5 FBH. This production inspection was used to set the program goal of four times 

improvement relative to a #5 FBH, which is equivalent to a #2.5 FBH as the goal. This 

inspection was not duplicated in the laboratory, and no data were obtained on the program. 

However, laboratory tests, using the same immersion transducers employed in the IN718 

evaluation, were conducted to gather data on the Waspaloy calibration billet, providing a 

comparison with the immersion multizone inspection results. 

This inspection was performed at the GE-QTC laboratory facility using test parameters similar to 

those applied to IN718. The zone 2 inspection was conducted using a 5′′ water path. A second 

experimental inspection using a shorter (2′′) water path was also completed to evaluate the effect 

of moving the zone 2 focal point deeper into the billet. 

Both transducers were calibrated on the shallowest #3 FBH in the same manner as the IN718 

test. The scan of each hole was gated just short of the inner-machined surfaces in order to 

produce clearer C-scans of all holes by eliminating the large reflection produced by each of the 

surfaces. The two-zone laboratory inspection calibrated to a #3 FBH, produced the C-scans 

shown in figure 3-9. The zone 1 transducer C-scan indicates all the #3 and #2 FBHs can be 

identified. The zone 2 transducer C-scan identifies the #3 FBH down to a depth of about 4′′. 

The #2 FBHs are difficult to distinguish from the background at depths greater than about 3.6′′. 

Note that the noise level is a more significant factor in Waspaloy than in IN718. The noise level 

shown at the extreme left side of the figure 3-9 C-scan (75% peak amplitude, 38% mean 

amplitude) was taken with the full gate in an area of the billet that did not contain FBHs and is 

indicative of the noise that would be encountered in a conventional immersion inspection of 

production billets. 

3-14
FIGURE 3-9. C-SCAN OF CONVENTIONAL INSPECTION ZONES 1 AND 

2 OF A WASPALOY CALIBRATION STANDARD 

The multizone inspection was also conducted at GE-QTC in the laboratory tank using 

transducers manufactured to the same specification as production transducers. A total of six 

zones were inspected using the same 5-MHz transducers developed for Ti billet inspections. The 

transducers were calibrated on the #2 FBH, with the individual gain levels adjusted to produce an 

80% FSH at the least reflective of the three FBHs in each zone. The C-scans for each zone are 

shown in figure 3-10 and show that all the #2 FBHs were easily identified to the full depth of 

5.5′′. 

3-15
FIGURE 3-10. C-SCAN OF MULTIZONE INSPECTION ZONES 1-6 OF A WASPALOY 

CALIBRATION STANDARD 

• Comparison to Program Goal. 

The same sensitivity calculations were performed on the Waspaloy data, resulting in the 

data presented in figure 3-11. The zone 1 laboratory conventional immersion inspection 

exceeded the program goal, while the zone 2 demonstrated a sensitivity of about #3.5 

FBH. The multizone inspection exceeded the program goal of #2.5 FBH by about 4 to 20 

times, depending on the zone. The average capability of multizone inspection was 

between #0.7 and #1.2 FBHs for all zones. 

The 5′′ water path for zone 2 conventional laboratory immersion inspections of Waspaloy 

does not provide the optimum inspection that is possible with the conventional 

transducers. At a 2′′ water path, the laboratory conventional zone 2 Waspaloy inspection 

improves to about a #2.8 FBH sensitivity. Contrary to the IN718 results, these data 

3-16
indicate a beneficial effect of focusing the conventional immersion transducer deeper in 

the Waspaloy billet. 

FIGURE 3-11. COMPARISON OF MULTIZONE INSPECTION CAPABILITY TO 

WASPALOY 10′′ BILLET PROGRAM GOAL AND LABORATORY 

CONVENTIONAL IMMERSION INSPECTION CAPABILITY 

3.2.9 Summary of Laboratory Evaluations. 

The results from both the IN718 and Waspaloy 10′′ billet conclusively demonstrate that the 

program goals can be achieved, and exceeded, using the same multizone transducers designed 

for Ti billet inspection in Phase I of the ETC program. Therefore, it was decided that no new 

transducers would be designed in this task. Results using the conventional transducers were also 

quite encouraging, given the improved sensitivity over current requirements. 

3.3 LABORATORY DEMONSTRATION. 

One of the steps to be completed prior to the pilot lot inspection or factory demonstration was a 

demonstration of the improved inspection capability for 10-inch diameter IN718 and Waspaloy 

in a laboratory setting using the calibration standards. Although the demonstration required only 

ETC members to participate, the team decided to invite all Ni billet suppliers, inspection houses, 

and aircraft engine manufacturers outside the ETC. 

3-17
On October 30, 2001, the GE-QTC hosted a 1-day review of the Nickel Billet Inspection 

Development program that included the laboratory demonstration of the multizone inspection. 

Attendees included representatives from Alvac, Wyman-Gordon, Special Metals, Carpenter 

Technology, and West-Penn NDT as well as the Federal Aviation Administration (FAA) and 

ETC team members. The agenda included a presentation of the results of the standards 

evaluation for both conventional and multizone approaches followed by a laboratory 

demonstration of the multizone inspection for a couple of the deeper zones in the standards. The 

improved inspection sensitivity was accomplished by successful application of the ultrasonic 

multizone inspection process developed for Ti billet to Waspaloy and IN718. Minor adjustments 

to the transducer water paths to achieve zone balance were the only changes required to inspect 

the Ni billet compared to the established Ti inspection. The program goals of a four times 

improvement in sensitivity over conventional inspection for billets up to 10′′ in diameter were 

not only met, but also substantially exceeded. 

3.4 FACTORY PILOT LOT ASSESSMENT. 

A request was forwarded to several production facilities to bid on the multizone inspection of 

several heats of production Ni billet. During the pilot program, a select number of indications 

found with multizone were purchased with preference given to those not rejected with 

conventional inspection. Ultrasonic and metallographic characterizations were performed on 

these indications for use in PoD studies and future inspection implementation decisions. The Ni 

billet inspection facility was contracted to inspect 75,000 pounds of 10′′ diameter IN718 billet 

and 25,000 pounds of 10′′ diameter Waspaloy billet using their existing multizone facilities. The 

10′′ diameter IN718 and Waspaloy standards were shipped to their facility to be used for 

inspection calibration. 

A visit was made to the inspection supplier at the beginning of the factory evaluation. During 

the 2-day meeting, the primary objective was to demonstrate calibration on the IN718 10′′

diameter billet standard and to collect data for the proposed sensitivity level. The same 

production transducers that were used for Ti multizone inspection were calibrated on the IN718 

standard, and C-scans were acquired for each zone. Table 3-3 shows the calibration and noise 

statistics for each zone at #1 FBH equal to 80% calibration level. 

Due to intermittent electronic noise present at the time of the evaluation, a C-scan was not made 

for zone 1. The noise was not a result of near-surface resolution; however, static measurements 

on zone 1 FBHs, indicated that the target calibration was achievable. The noise problem was 

corrected prior to the time of inspection. After the ETC members reviewed the data, it was 

agreed to increase the gain level for each zone by 6 dB over the calibration level. The only 

exception was zone 1 for which instrumentation limitations only allowed a 4 dB additional gain. 

The increase in sensitivity increased the average material noise to a higher level and reduced the 

rounding variability for the signal-to-noise calculation used in the evaluation software when 

noise levels are low. 

The Waspaloy standard was not available at the time of this visit for calibration purposes. It was 

being machined to eliminate surface irregularities. The Waspaloy standard was machined and 

delivered to the facility after the visit. 

3-18
TABLE 3-3. CALIBRATION AND NOISE STATISTICS FOR #1 FBH SENSITIVITY 

ON IN718 STANDARD 

Stats From Solid End of Standard 

Zone 

Water Path 

(microsec.) 

Water Path 

(inches) 

Attenuation 

Setting 

Target 

Depth 

#1 FBH 

Amplitude

Min. 

Noise 

(%) 

Max. 

Noise 

 (%) 

Mean 

Noise 

 (%) 

Std. 

Dev. 

(%) 

1 130 3.79 4 

0.2 

0.55 

0.9 

83 

95 

89 

System noise prevented getting 

numbers 

2 125 3.64 29 

0.9 

1.35 

1.8 

84 

104 

81 

2 15 6 1 

3 140 4.08 23 

1.8 

2.25 

2.7 

80 

99 

81 

1 11 3 1 

4 130 3.79 26 

2.7 

3.15 

3.6 

80 

95 

84 

2 9 4 1 

5 120 3.5 22 

3.6 

4.05 

4.5 

80 

92 

80 

2 13 5 1 

6 125 3.64 19 

4.5 

5 

5.5 

90 

93 

81 

4 17 8 2 

The IN718 inspection required calibration to a #1 FBH sensitivity and the Waspaloy to a #2 FBH 

sensitivity. Details of the inspection procedure and the metallographic data required for PoD 

analysis were reviewed with ETC team members responsible for reliability efforts of the 

program. Members of the PoD group had input the type of data that would be most useful for the 

PoD assessment. Additions to the normal six-zone inspection included two channels dedicated 

to the collection of conventional two-zone C-scan inspection and, if possible, back-wall 

attenuation C-scans. Although not originally planned, this request made it necessary to install 

additional instrumentation at the factory. This included two portable ultrasonic instruments and 

a voltage conditioner circuit to make the output of the portable machines compatible with the 

multizone instrumentation. 

After the additional equipment was delivered to the factory, instructions were that multizone 

inspection and the modified C-scan conventional inspection would be performed following 

normal production material inspection procedures. These higher sensitivity inspections were not 

to be a substitute for the production inspections. The ETC planned to purchase six indications 

from IN718 and two from Waspaloy. Indications would be reported to the ETC and a decision to 

purchase the indication agreed upon. The ETC team hoped to have indications from both 

double- and triple-melt products. However, availability would be subject to the supplier’s 

production orders. 

3-19
3.5 FACTORY DEMONSTRATION. 

Once the factory had conducted an initial inspection of some production material at the higher 

sensitivity, plans were made for hosting a demonstration for the industry. The factory 

demonstration took place on February 21, 2003. This 1-day event provided an opportunity for 

the FAA, ETC members, and Ni billet producers to see firsthand how the multizone inspection 

functioned in an industrial setting. Following a brief introduction by the factory quality and 

safety managers, ETC team members provided an overview of the entire ETC program covering 

all of the development efforts and a technical review of the Ni billet program. Finally, the 

factory host made a presentation dealing with the technical aspects and cost differences between 

conventional and multizone inspections. Some of the highlights from the factory presentation 

indicated that the multizone inspection for Ni was comparable to the multizone inspection of 

current production Ti product. 

The company that performed the factory demonstration had approximately 2 years of experience 

in multizone inspection of Ti billet and over 20 years in the conventional inspection of all types 

of billet. This experience provided a reasonable baseline from which to compare the multizone 

inspection for Ni billet with conventional tests. All cost factors associated with the multizone 

inspection were tracked. In addition to the costs directly associated with calibration and billet 

scanning, other costs such as potential changes in surface finish requirements and postinspection 

evaluation of indications were accounted for. False calls were to be factored into the associated 

costs if some of the indications prove to be noise-related. 

Costs associated with the improved sensitivity multizone inspection fall principally into two 

categories: (1) the initial investment costs of the equipment and the costs associated with the 

maintenance of that equipment and (2) costs that are associated with productivity of the process, 

which include material preparation, setup, scanning and evaluation time, and training. The 

factory was asked to keep records of the cost differentials associated with the multizone 

inspection of the Ni. In the case where it would be difficult to acquire the relative costs of the 

demonstration, they used historical data based on the Ti multizone inspection. An example of 

this would be for equipment and transducer replacement. 

A difficult cost to predict was the loss of material due to increase in sensitivity or the evaluation 

of false calls. These values are very difficult to arrive at because there is no established reject 

level and generally requires sustained long-term inspection to get an adequate projection. If the 

reject level were set equivalent to a #1 FBH sensitivity, then none of the material inspected from 

the 80,000 pounds of IN718 would have been rejected. If, on the other hand, the reject criteria 

were for all signals greater than or equal to 2.5 SNR, then a good deal of material would have 

been rejected. Setting a reject level was not the purpose of this task. However, upon the 

characterization of the four indications and review by the PoD and engineering communities, 

these levels may come under review. It is sufficient to say that if the sensitivity level is 

increased from #2 or #3 FBHs to #1 FBH, the long-term effect will be that more material 

containing anomalies is going to be rejected. 

Equipment investment costs for multizone inspection were the first to be compared to 

conventional inspection. The multizone inspection investment for the instrument, standards, and 

transducers would total approximately $360,000 and cover four different diameter billets verses 

3-20
about $50,000 for a conventional two-zone inspection capability. The cost for multizone 

inspection transducers is about $60,000 to $80,000, which at this point, has limited suppliers. 

Facilities that use multizone to inspect Ti and process both Ti and Ni products might not have to 

incur these added transducer costs, since the same transducers are used for both materials. There 

is about a seven-fold increase in investment required to install an eight-channel multizone system 

over a conventional system. A survey of the equipment manufacturer who supports five 

multizone inspection facilities indicated that replacement cost across the industry have been 

running on average about $5,000 to $10,000 yearly for each of the Ti inspection facilities. This 

number is expected to be the same for Ni inspection. Out of a set of 20 transducers covering four 

billet diameters, it is likely that two transducers a year will need to be replaced at a cost of 

$10,000. Therefore, multizone maintenance costs are estimated to be about $18,000 per year. 

The cost cannot be compared to current maintenance costs, since data on conventional 

maintenance were unavailable. 

Of initial importance was the determination of whether the surface finish used for conventional 

inspection was adequate for the increased sensitivity of the multizone inspection test. The 

factory reported that no additional surface preparation was required to inspect the 10′′ billet that 

was used for this factory evaluation. However, the supplier that participated in the evaluation 

noted that the multizone test is more sensitive to surface blemishes than conventional inspection. 

Table 3-4 is a comparison summary that was presented at the production site by the factory 

personnel that indicates their experience when comparing the conventional and multizone 

procedures with respect to labor and machine hours. 

TABLE 3-4. MULTIZONE VS CONVENTIONAL—INVESTMENT, MAINTENANCE, 

LABOR, AND OPERATING COST COMPARISONS 

Multizone Conventional 

Investment $360,000 $50,000 

Maintenance $17,000/yr Not available 

Setup 2-4 hrs 0.5 hr 

Scanning Multizone 36% longer than conventional 

Analysis 0.5-1 hr 0 

Evaluation 0-2 hrs 0-1 hr 

3.6 INDICATION CHARACTERIZATION. 

Over the course of 1 year (August 2002-August 2003), the factory inspected 81,000 pounds of 

IN718, which included 33,000 pounds of double melt and 48,000 pounds of triple melt. During 

this time, no 10′′ diameter Waspaloy billet was inspected because of the lack of orders placed for 

this material. Of the IN718 material inspected, there were a total of 19 indications that had an 

SNR of 2.5 or greater. Although none of the indication amplitudes equaled the #1 FBH 

calibration level, five had amplitudes exceeding the 50% evaluation threshold. Note that all 19 

of the indications were undetected by the conventional billet inspection method that was 

calibrated to a lower sensitivity, and therefore, is not expected to be sensitive to anomalies with 

these small ultrasonic responses. Indications were detected based on the production multizone Ti 

3-21
evaluation software that identifies signals in the C-scan image that have a local SNR > 2.5 or 

exceed an amplitude threshold of 50%. The ETC was able to purchase five of these indications. 

Table 3-5 shows a summary of the indications identified, and the ones that were removed for 

metallographic evaluation. 

TABLE 3-5. LIST OF INDICATIONS AND THE AMPLITUDES RELATIVE TO 

#1 AND #2 FBH CALIBRATIONS 

Multizone Indication Summary 

IN718 

Zone 

Detected 

Depth 

(in.) 

Amp. 

% FSH SNR 

Indication 

Length 

Amp. to 

#1 FBH 

Amp. to 

#2 FBH Removal 

Triple Melt 3 2.79 28 3.7 0.15 14 3.5 

Triple Melt 4 2.79 38 3.33 0.2 19.2 4.8 

Triple Melt 5 3.89 66 4.26 0.3 33.2 8.3 

Triple Melt 6 4.01 58 2.84 0.57 29.2 7.3 

Triple Melt 5 4.4 45 3.44 0.3 22.8 5.8 Cut out 

Triple Melt 3 1.375 29 3.11 0.33 14.4 3.6 Cut outnot found 

Triple Melt 5 4.375 67 4.91 0.19 33.6 8.4 Cut out 

Double Melt 6 5.15 88 3.4 0.45 44 11 Cut out 

Double Melt 3 1.7 41 11.3 0.18 20.4 5.1 Cut out 

Double Melt 3 1.5 12 2.89 0.12 6 1.5 

Double Melt 2 0.61 9 2.51 0.28 4 1 

Double Melt 2 1.5 7 2.51 0.4 4 1 

Double Melt 3 1.8 8 2.84 0.07 4 1 

Double Melt 2 0.7 5 2.72 0.13 4 1 

Double Melt 2 1.8 5 2.72 0.07 4 1 

Double Melt 4 3.8 13 5.6 0.15 12 3 

Double Melt 5 3.9 7 2.7 0.07 8 2 

Double Melt 4 3.4 53 15.18 0.4 48 12 

Double Melt 4 3.9 16 3.55 0.14 16 4 

The procedure for removing the indications from the billet is shown in figure 3-12. Side 1 of the 

removed cube is facing the direction in which the indication was originally found. Four 

indications were sent to ISU for ultrasonic characterization. This is a procedure that examines 

the indications from all sides of a 1-inch cube at several of different frequencies and resolutions. 

Appendix A contains the detailed sonic and metallographic data and analysis for each of the four 

indications. 

3-22
Top=1

Billet axis

Front=6

Right=4

UT beam direction Left=2

BOT=3

Back=5 

FIGURE 3-12. SCHEMATIC OF INDICATION REMOVAL FROM BILLET WITH 

ASSOCIATED ORIENTATION LABELS 

Once an indication was identified and approved by the ETC for evaluation, a detailed ultrasonic 

and metallographic evaluation procedure was followed. Appendix B provides a copy of the 

ultrasonic procedure. This includes removing the cube that contains the indication and then 

ultrasonically characterizing the indication from six sides as well as computed tomography x-ray 

examination. The x-ray results were inconclusive because of the size constraints of the sample. 

Finally, the indication was sectioned using an existing detailed metallographic procedure so that 

the full extent of the size and shape is known. The indication also underwent a chemical 

microprobe at one step during the step-polishing routine. 

3.7 SUMMARY OF 10′′ DIAMETER BILLET ASSESSMENT. 

• Billet converted with GFM processing is more acoustically noisy than billet converted 

using V-Die processing. GFM material was selected for use in calibration standards 

since this provides a more conservative assessment. 

• Transducer characterization procedures were developed for bicylindrically focused 

transducers, which are useful for ensuring that actual focal characteristics match the 

intended design values. 

• The Waspaloy calibration standard was more ultrasonically noisy than the IN718 material 

(75% peak noise compared to 20%, respectively) when measured with the same 

calibration target. 

• The multizone inspection procedure and transducers originally used for Ti easily 

exceeded the program goal of #1 FBH for IN718 and #2.5 FBH for Waspaloy. The 

multizone system exceeded the IN718 goal by a minimum of 3.5 times and was a 

minimum of 31 times more sensitive than the current inspection requirement. Multizone 

exceeded the Waspaloy goal by a minimum of 4 times and was a minimum of 14 times 

more sensitive than the current inspection requirement. 

• The use of conventional transducers in the two-zone laboratory inspection nearly met the 

program goal for IN718. The laboratory conventional immersion inspection exceeded the 

3-23
program goal of #2.5 FBH sensitivity for Waspaloy in the near-surface zones. No data 

was gathered for the production conventional contact inspection of Waspaloy. 

• The factory assessment showed that the surface finish used for conventional inspection 

was adequate for the increased sensitivity of the multizone inspection test, although the 

multizone test is more sensitive to surface blemishes. 

• The factory assessment showed comparable characteristics for inspection of Ni when 

compared to experience with inspection of Ti multizone procedures. 

• A cost comparison revealed increased investment and operational cost for multizone 

inspection compared to conventional inspection. 

• Suppliers expressed concerns regarding transducer manufacturability and limited 

availability of transducer vendors. 

• The factory demo on 81,000 pounds of two and three times melted IN718 generated 

conclusive results that the multizone system can detect indications that are missed by the 

current conventional inspection. A total of 19 indications were detected by multizone, all 

of which were significantly smaller than conventional inspection requirements that are at 

a #2 FBH sensitivity and, therefore, below the threshold for detection. 

3.8 SMALL-DIAMETER BILLET STUDY. 

In addition to the inspection of large (10′′)-diameter billet, the ETC team also completed an 

evaluation of the inspection of small-diameter billet. The objective was to evaluate and compare 

the capability of the different ultrasonic inspection techniques, including conventional, single 

transducer (ST) multizone, and phased array inspection on 5′′ diameter Ni and Ti alloys. The 

results for both materials are discussed below. 

The 5′′ diameter ETC billet reference standards (Waspaloy and Ti-6Al-4V) containing #1 and #2 

FBHs were inspected using conventional, ST multizone, and phased array ultrasonic inspection 

techniques to evaluate the relative performance of these techniques for small-diameter billet. 

The geometry of the standard is illustrated in figure 3-13 along with the location of all the FBHs. 

All the inspection techniques were done in immersion. The collected data from the different 

inspection techniques were then analyzed, and a detailed comparison was conducted. This 

section summarizes the results of the small-diameter billet study. 

3-24
FIGURE 3-13. THE 5′′ DIAMETER ETC BILLET REFERENCE STANDARDS 

(WASPALOY AND Ti-6Al-4V) CONTAINING #1 AND #2 FBHs 

3.8.1 Inspection Setup and Results for Waspaloy. 

The 5′′ diameter Waspaloy reference small billet standard having #1 and #2 FBHs was scanned 

on a Sonix system. The inspection sensitivity was equivalent to a conventional production 

Waspaloy scan calibrated to 80% FSH using a #3 FBH. To achieve this sensitivity, 7 dB was 

removed after setting up a DAC curve using the #2 FBHs. The DAC used in these 

measurements is shown in table 3-6. The transducer used was S/N RB0802, with a 0.75′′

diameter element and 6′′ nominal focus (I8 type). This is typical of the 5-MHz spherically 

focused transducers that would be used to inspect 5′′ diameter Waspaloy billet, which was 

determined by polling several billet inspection facilities. A 5′′ water path was used. The 

conventional inspection and ST were done on a Sonix system with the following parameters: 

• Pulser Voltage: 425 V A/D gain: 10 V 

• Gain: 43 dB + Electronic distance-amplitude correction (EDAC) A/D offset: 2036 

• Filter: HP 2-25 MHz, LP off Impedance: Low 

• Energy: 4 Sample rate: 100 MHz 

TABLE 3-6. THE EDAC FOR WASPALOY CONVENTIONAL AND ST INSPECTIONS 

EDAC Point 

Gain (dB) 

(Total = 43+) 

Time 

(μsec) 

1 0 2.09 

2 1.27 4.39 

3 4.88 6.66 

4 9.12 9.85 

5 13.34 12.96 

6 16.00 16.11 

7 17.87 19.20 

8 20.22 22.48 

9 22.57 25.63 

3-25
Figure 3-14 shows the C-scan resulting from the conventional and ST inspections of the 5′′

diameter Waspaloy billet reference standard along with a C-scan illustrating the back-wall echo 

from the standard. Table 3-7 summarizes the SNR results extracted from the C-scan for #2 and 

#1 FBHs, respectively. The SNR was calculated using the following equation: 

PeakSignal-AverageNoise SNR = 

PeakNoise-AverageNoise (3-1) 

which is an industry-acceptable definition of SNR. The peak signal was measured directly from 

the C-scan by drawing an appropriate rectangle around the indication, whereas the peak noise 

and average noise were determined by selecting an appropriate noise area close to the indication 

of interest for the case of ST inspection. As for the conventional inspection, the peak and 

average noise values were determined based on the whole volume of the billet inspected. The 

average noise was approximately 18% FSH with a #2 FBH calibration and at 36% FSH in deep 

zones. Note that the #2 FBH was essentially undetectable (i.e., SNR < 2.0) at depths greater than 

about 2.25′′, while the #1 FBH was undetectable at depths of greater than about 1.87′′. 

Backwall

FIGURE 3-14. SINGLE TRANSDUCER INSPECTION C-SCAN OF THE 5′′ DIAMETER 

WASPALOY BILLET 

3-26
TABLE 3-7. SIGNAL-TO-NOISE RATIO FOR CONVENTIONAL AND ST INSPECTIONS 

OF 5′′ DIAMETER WASPALOY BILLET REFERENCE STANDARD 

FBH 

FBH 

Depth 

(in.) 

FBH Peak 

Amplitude 

(% screen) 

Noise 

Peak 

Amplitude 

(% screen)

Mean 

Noise 

Amplitude 

(% screen) 

ST 

SNR 

ST 

SNR 

(dB) 

Conventional 

 SNR 

Conventional 

SNR 

(dB) 

0.20 39.2 5.5 2.90 13.962 22.90 1.059 0.50 

0.48 33.7 5.5 3.40 14.429 23.18 1.059 0.50 

0.75 34.5 5.5 2.15 9.657 19.70 1.059 0.50 

1.13 32.9 9.4 3.86 5.232 14.37 1.059 0.50 

1.50 32.9 11.8 5.74 4.482 13.03 1.059 0.50 

1.87 36.1 15.7 7.98 3.642 11.23 1.059 0.50 

2.25 34.5 19.6 9.37 2.457 7.81 1.059 0.50 

2.63 27.5 21.2 10.80 1.606 4.11 1.059 0.50 

#2 FBH Waspaloy 

3.00 26.7 25.9 12.30 1.059 0.50 1.059 0.50 

0.20 26.7 11.8 6.50 3.8 11.62 1.740 4.81 

0.48 32.9 12.9 7.20 4.5 13.08 1.740 4.81 

0.75 25.9 11.0 7.40 5.1 14.22 1.740 4.81 

1.13 27.5 12.5 8.00 4.3 12.74 1.740 4.81 

1.50 35.3 18.8 10.60 3.0 9.58 1.740 4.81 

1.87 36.9 22.0 10.80 2.3 7.35 1.740 4.81 

2.25 32.9 23.5 10.80 1.7 4.81 1.740 4.81 

2.63 - 27.4 11.80 - - - - 

#1 FBH Waspaloy 

3.00 - 27.4 12.80 - - - - 

Upon completion of the conventional and ST inspections, the Waspaloy standard was inspected 

using a multizone inspection procedure. For this study, the standard GE production multizone 

transducers were applied to the 5′′ diameter Waspaloy and Ti reference standards. Four zones 

are used to examine the depth from 0.2′′ to 3.0′′ with each zone covering about 0.75′′ of material. 

Table 3-8 summarizes the transducer specifications and gating requirements associated with each 

zone. For 5′′ diameter billet, the transducers were positioned at approximately 3.5′′ water path, 

and the instrument sensitivity adjusted to make the highest amplitude signal in each zone close to 

80% FSH. This is somewhat different from the normal procedure in that the lowest amplitude 

target is raised to 80%. This prevented any calibration targets from being saturated during 

scanning. C-scans (as shown in figure 3-15) were then made of each calibration target at a 

0.020′′ index and a shortened gate that excluded the back wall at each step. The target 

amplitude, maximum, and mean noise values were taken from the image statistics in each zone 

and used to determine the SNR values summarized in table 3-9 using equation 3-1. Due to the 

increased gain level required for #1 FBH calibration, the zone 1 transducer was not able to 

clearly resolve the 0.2′′ deep target and caused the lower than normal signal-to-noise value. This 

particular zone will require some added development in near-surface resolution to bring this 

value in closer agreement with other zones. 

3-27
TABLE 3-8. MULTIZONE PRODUCTION TRANSDUCERS 

Zone 

Coverage 

(in.) 

Gate 

(μsec) Pulse/rev 

Element Diameter 

(in.) 

Designed Focus 

(in.) 

1 0.2-0.75 0.2-1.15 1024 0.75 0.4 

2 0.75-1.5 0.35-1.9 1024 1.0 1.2 

3 1.5-2.25 1.1-2.65 512 1.375 2.1 

4 2.25-3.0 1.85-3.5 512 1.75 3.0 

FIGURE 3-15. FOUR ZONES OF MULTIZONE INSPECTION C-SCANS THAT 

COVER A DEPTH OF 3′′ INTO THE BILLET 

3-28
TABLE 3-9. SIGNAL-TO-NOISE RATIO FOR MULTIZONE INSPECTION OF 5′′

DIAMETER WASPALOY BILLET REFERENCE STANDARD 

FBH 

FBH 

Depth 

(in.) 

Attenuation 

(dB) 

FBH Peak 

Amplitude 

(% FSH) 

Noise 

Peak 

Amplitude 

(% FSH) 

Mean 

Noise 

Amplitude 

(% FSH) 

Multizone 

Inspection 

SNR 

Multizone 

Inspection 

SNR 

(dB) 

0.20 35.50 225.5 45.0 37.00 23.56 27.44 

0.48 35.50 220.0 12.0 8.00 53.00 34.48 

0.75 32.50 151.8 12.0 9.00 47.60 33.55 

0.75 36.50 211.4 12.0 3.00 23.15 27.29 

1.13 38.50 261.3 9.0 4.00 51.45 34.23 

1.50 36.00 187.9 10.0 4.00 30.65 29.73 

1.50 27.00 125.1 14.0 6.00 14.88 23.45 

1.87 29.50 185.9 15.0 6.00 19.99 26.01 

2.25 28.50 227.7 15.0 7.00 27.59 28.81 

2.63 27.00 240.3 18.0 8.00 23.23 27.32 

#2 FBH 

Waspaloy 

3.00 25.00 205.5 22 7.00 13.24 22.44 

0.20 26.50 80.0 44.0 38.00 7.00 16.90 

0.48 24.50 62.0 11.0 8.00 18.00 25.11 

0.75 22.50 48.0 12.0 8.00 10.00 20.00 

0.75 27.50 75.0 9.0 4.00 14.20 23.05 

1.13 28.00 78.0 12.0 5.00 10.43 20.36 

1.50 24.50 50.0 9.0 4.00 9.20 19.28 

1.50 18.50 47.0 12.0 6.00 6.83 16.69 

1.87 21.50 74.0 14.0 6.00 8.50 18.59 

2.25 16.00 54.0 26.0 13.00 7.00 16.90 

2.25 18.50 73.0 30.0 8.00 2.95 9.41 

2.63 17.00 76 19 8.00 6.18 15.82 

#1 FBH 

Waspaloy 

3.00 15.00 65 16 8.00 7.13 17.06 

The 5′′ diameter Waspaloy billet reference standard that has #2 and #1 FBHs at the depths shown 

in figure 3-13 was also scanned using Honeywell’s 5-MHz annular sectorial phased array 

transducer [25]. Figure 3-16 shows the layout of the 113 elements on the face of the 5-MHz 

phased array transducer that was designed for the inspection of 5′′ to 8′′ diameter billets. The 

113 elements were connected such that symmetrical elements are fired at the same time. This 

way, fewer channels are needed to drive the probe. The inspection was performed in an 

immersion tank that was designed for the inspection of Ti billets with a rotational axis and an 

index axis. After each rotation of the billet, a mechanical step is made on the index axis. 

Figure 3-17 shows a schematic of the mechanical setup used in the scanning of the billet standard 

using the 5-MHz phased array transducer. 

3-29
FIGURE 3-16. LAYOUT OF THE 113 ELEMENTS ON THE FACE OF THE 

5-MHz PHASED ARRAY TRANSDUCER 

FIGURE 3-17. THE MECHANICAL SETUP USED IN THE SCANNING OF 

THE BILLET STANDARD 

The standard focusing technique was used in this study. In this technique, the focus point in 

emission is the same as the focus point in reception. For each hole, the focusing is made 

(theoretically) at the exact depth of the defect. The gain is adjusted so that the echo from the 

defect appears on the screen with reasonable amplitude. A short scan is performed around each 

hole. All the A-scan data were saved so that the entire inspected volume could be reconstructed 

after the data acquisition. The water path was held at 4′′ throughout the inspection. Table 3-10 

shows some inspection parameters used for each of the FBHs in the billet standard. 

3-30
TABLE 3-10. PHASED ARRAY INSPECTION PARAMETERS FOR THE WASPALOY 

5′′ DIAMETER BILLET STANDARD 

FBH Depth 

(in.) 

ER-Focus 

(in.) 

Beam Size 

(mils) 

Gain 

(dB) 

3 3 100 15 

2.63 2.63 100 15 

2.25 2.25 100 10 

1.87 1.87 100 10 

1.5 1.5 100 13 

1.13 1.13 100 13 

0.75 0.75 100 13 

0.48 0.48 100 15 

0.2 0.2 100 20 

Frequency = 5 MHz 

Water Path = 4 inches 

Figure 3-18 shows typical results collected during the inspection for the #2 and #1 FBHs at a 

1.5′′ depth. The figure shows the top (C), side (B), and the end (D) scans along with two A-scans 

showing the indications for the #2 and #1 FBHs. Appendix C shows similar scans for the rest of 

the holes at all remaining depths in the Waspaloy standard. 

 C D 

 B 

FIGURE 3-18. TYPICAL RESULTS COLLECTED DURING THE INSPECTION FOR THE 

#2 AND #1 FBHs AT A 1.5′′ DEPTH 

3-31
The SNR was calculated according to equation 3-1. The noise was measured using the contour 

tool in Tomoview, the proprietary software delivered with the R/D Tech phased array system 

hardware. A contour is drawn on a desired region over the C-scan. The tool measures the mean 

noise and the maximum noise in the region. Table 3-11 shows the SNR results collected during 

the inspection. A comparison of the SNR data shown in tables 3-7, 3-9, and 3-11 suggest the 

phased array sensitivity is greater than the conventional and ST inspections sensitivity but lower 

than the multizone sensitivity in the near-surface zone. At larger depths, the sensitivity of the 

phased array and multizone inspections is the same. 

TABLE 3-11. SIGNAL-TO-NOISE RATIO RESULTS COLLECTED DURING THE 

PHASED ARRAY INSPECTION OF THE 5′′ DIAMETER WASPALOY 

REFERENCE BILLET STANDARD 

FBH 

Depth 

(in.) 

Peak Signal

(% FSH) 

Peak 

Noise 

(% FSH) 

Average 

Noise 

(% FSH) SNR 

SNR 

(dB) 

0.2 50.2 18 13.5 8.16 18.23 

0.48 59.6 12.9 7.6 9.81 19.83 

0.75 84.3 9 4.8 18.93 25.54 

1.13 89.4 11.95 5.3 12.65 22.04 

1.5 76.5 9.4 4.7 15.28 23.68 

1.87 85.1 7.8 4 21.34 26.58 

2.25 64.3 8.6 2.9 10.77 20.65 

2.63 62.7 11 3.9 8.28 18.36 

#2 FBH 

Waspaloy 

3 89 9.8 4 14.66 23.32 

0.2 14.1 11.4 5.5 1.46 3.27 

0.48 16.1 12.9 7.6 1.60 4.10 

0.75 25.1 9 4.8 4.83 13.68 

1.13 21.6 11.95 5.3 2.45 7.79 

1.5 21.6 9.4 4.7 3.60 11.12 

1.87 23.1 7.8 4 5.03 14.02 

2.25 19.6 8.6 2.9 2.93 9.34 

2.63 20.4 11 3.9 2.32 7.32 

#1 FBH 

Waspaloy 

3 22 9.8 4 3.10 9.84 

3.8.2 Inspection Setup and Results for Ti-6Al-4V. 

The same techniques, namely, conventional, ST element, multizone, and phased array 

inspections, were used to inspect the 5′′ diameter Ti-6Al-4V billet reference standard. The 

general procedure was the same as the one used for the Waspaloy standard with some minor 

differences, as described below. 

The first step was completion of a conventional and ST inspections of the Ti billet standard. The 

transducer used in this case (figure 3-19) was S/N 98G097 from Timet Witton in Birmingham, 

3-32
England. This is a typical 5-MHz, cylindrically focused transducer with which Timet would 

inspect the 5′′ diameter Ti billet. The line focus was a nominal 6′′ in water and a 4′′ water path 

was used. The inspection sensitivity was equivalent to a conventional production Ti scan 

calibrated to 80% FSH using a #3 FBH. To achieve this sensitivity, 7 dB was removed after 

setting up a DAC curve using the #2 FBHs (see table 3-12). The conventional and ST 

inspections of the 5′′ diameter Ti-6Al-4V billet reference standard was done on a Sonix system 

with the following parameters: 

• Pulser Voltage: 400 V A/D gain: 10 V 

• Gain: 43 dB + EDAC A/D offset: 2036 

• Filter: HP 2-25 MHz, LP off Impedance: Low 

• Energy: 4 Sample rate: 100 MHz 

FIGURE 3-19. SIXTY-INCH CYLINDRICALLY FOCUSED TRANSDUCER 

(Courtesy of Timet Witton) 

TABLE 3-12. ELECTRONIC DISTANCE-AMPLITUDE CORRECTION FOR 

Ti-6Al-4V CONVENTIONAL AND ST INSPECTIONS 

EDAC 

Point 

Gain (dB) 

(Total = 43+) 

Time 

(μsec) 

1 4.40 1.76 

2 3.61 4.23 

3 3.30 6.36 

4 6.59 9.44 

5 7.22 12.58 

6 9.57 15.69 

7 10.36 18.83 

8 12.24 21.94 

9 13.81 24.96 

3-33
Figure 3-20 shows the C-scan resulting from the ST inspection of the 5′′ diameter Ti-6Al-4V 

billet reference standard along with a C-scan illustrating the back-wall echo from the standard. 

Table 3-13 summarizes the SNR results extracted from the C-scan for #2 FBH. Note that the #2 

FBHs were essentially detected with SNR <2.0 at depths greater than 2.25′′. All of the #1 FBHs 

were undetectable in this case. The SNR was calculated using equation 3-1. 

Backwall 

FIGURE 3-20. C-SCAN OF ST INSPECTION OF THE 5′′ DIAMETER Ti BILLET 

TABLE 3-13. SIGNAL-TO-NOISE RATIO FOR CONVENTIONAL AND ST INSPECTIONS 

OF 5′′ DIAMETER Ti BILLET REFERENCE STANDARD 

FBH Size 

FBH 

Depth 

(in.) 

FBH Peak 

Amplitude 

(% screen) 

Noise Peak 

Amplitude 

(% screen) 

Mean Noise 

Amplitude 

(% screen) ST SNR 

ST SNR 

(dB) 

Conventional 

SNR 

Conventional 

SNR 

(dB) 

0.20 26.7 11.8 6.50 3.81 11.62 1.14 1.11 

0.48 32.9 14.9 7.30 3.37 10.55 1.14 1.11 

0.75 25.9 14.1 7.40 2.76 8.82 1.14 1.11 

1.13 27.5 15.7 8.50 2.64 8.43 1.14 1.11 

1.50 35.3 22.0 10.90 2.20 6.84 1.14 1.11 

1.87 36.9 23.5 12.80 2.25 7.05 1.14 1.11 

2.25 32.9 20.4 10.60 2.28 7.14 1.14 1.11 

2.63 32.9 25.9 11.80 1.50 3.50 1.14 1.11 

#2 FBH 

Ti-6Al-4V 

3.00 26.7 25.1 13.40 1.14 1.11 1.14 1.11 

After completing the conventional inspection, a multizone inspection was performed utilizing the 

procedure used for the 5′′ diameter Waspaloy billet standard. The C-scans resulting from this 

inspection are shown in figure 3-21, and the SNR calculated from these C-scans are listed in 

table 3-14. Note that all the #2 and #1 FBHs were detected with a SNR >2.0 at all depths down 

to the centerline of the billet standard. 

3-34
FIGURE 3-21. C-SCANS OF THE 5′′ DIAMETER Ti BILLET REFERENCE STANDARD 

(A total of four zones were used to cover a depth of 3′′ into the billet.) 

TABLE 3-14. SIGNAL-TO-NOISE RATIO FOR MULTIZONE INSPECTION OF A 

5′′ DIAMETER Ti BILLET REFERENCE STANDARD 

FBH 

FBH 

Depth 

(in.) 

Attenuation 

(dB) 

FBH Peak 

Amplitude 

(% FSH) 

Noise Peak 

Amplitude 

(% FSH) 

Mean Noise 

Amplitude 

(% FSH) 

Multizone 

SNR 

Multizone 

SNR 

(dB) 

0.20 40.0 274.7 43.0 28.00 16.44 24.32 

0.48 39.0 223.9 32.0 17.00 13.79 22.79 

0.75 36.5 167.5 30.0 16.00 10.82 20.68 

0.75 40.0 132.1 31.0 14.00 6.95 16.83 

1.13 41.0 185.0 29.0 14.00 11.40 21.14 

1.50 40.0 166.8 29.0 13.00 9.61 19.65 

1.50 32.5 196.1 30.0 14.00 11.38 21.12 

1.87 34.5 225.5 39.0 18.00 9.88 19.89 

2.25 33.0 158.9 40.0 18.00 6.40 16.13 

2.25 29.5 160.6 33.0 17.00 8.98 19.06 

2.63 31.0 197.3 43.0 20.00 7.71 17.74 

#2 FBH 

Multizone 

Ti 

3.00 27.5 126.8 32.0 18.00 7.77 17.81 

0.20 29.5 82.0 53.0 29.00 2.21 6.9 

0.48 29.5 75.0 35.0 16.00 3.11 9.8 

0.75 26.0 50.0 26.0 14.00 3.00 9.5 

0.75 33.0 59.0 26.0 12.00 3.36 10.5 

1.13 33.5 78.0 31.0 14.00 3.76 11.5 

1.50 29.0 47.0 26.0 13.00 2.62 8.4 

1.50 22.5 62.0 29.0 14.00 3.20 10.1 

1.87 25.5 80.0 29.0 17.00 5.25 14.4 

2.25 25.5 67.0 32.0 17.00 3.33 10.5 

2.25 23.0 76.0 33.0 17.00 3.69 11.3 

2.63 22.0 70.0 39.0 21.00 2.72 8.7 

#1 FBH 

Multizone 

Ti 

3.00 21.0 60 36 19.00 2.41 7.6 

3-35
The final inspection performed on the 5′′ diameter Ti standard was a phased array inspection. 

The procedure used for the 5′′ diameter Waspaloy billet standard was applied to the 5′′ diameter 

Ti billet standard. 

Table 3-15 shows some inspection parameters used for each one of the FBHs in the Ti billet 

standard. Figure 3-22 shows typical results collected during the inspection for the #2 and #1 

FBHs at a 1.5′′ depth. The figure shows the top (C), side (B), and the end (D) scans along with 

two A-scans showing the indications for the #2 and #1 FBHs. Appendix D shows similar scans 

for the rest of the holes at all remaining depths in the Ti standard. Again, the SNR was 

calculated according to equation 3-1. The noise was measured using the contour tool in 

Tomoview. A contour is drawn on a desired region over the C-scan. The tool measures the 

mean and maximum noises in the region. Table 3-16 shows the SNR results collected during the 

inspection. 

TABLE 3-15. PHASED ARRAY INSPECTION PARAMETERS FOR THE 

5′′ DIAMETER Ti BILLET STANDARD 

FBH Depth 

(in.) 

ER-Focus 

(in.) 

Beam Size

(mils) 

Gain 

(dB) 

3 3 100 10 

2.63 2.63 100 12 

2.25 2.25 100 13 

1.87 1.87 100 15 

1.5 1.5 100 12 

1.13 1.13 100 6 

0.75 0.75 100 15 

0.48 0.48 100 10 

0.2 0.2 100 15 

Frequency = 5 MHz 

Water Path = 4 inches

3-36
 C D 

 B 

FIGURE 3-22. TYPICAL RESULTS FOR THE #2 AND #1 FBHs AT A 1.5′′ DEPTH 

TABLE 3-16. SIGNAL-TO-NOISE RATIO RESULTS COLLECTED DURING THE 

PHASED ARRAY INSPECTION OF THE 5′′ DIAMETER 

Ti-6Al-4V REFERENCE BILLET STANDARD 

FBH Depth 

Peak Signal 

(% FSH) 

Peak 

Noise 

(% FSH)

Avg 

Noise 

(% FSH) SNR 

SNR 

(dB) 

0.2 71 22.4 11.2 5.34 14.55 

0.48 79.6 10.2 5.7 16.42 24.31 

0.75 74.1 8.6 4.8 18.24 25.22 

1.13 98.8 11.4 5.7 16.33 24.26 

1.5 78.4 13.7 6.9 10.51 20.44 

1.87 78 14.9 8.6 11.02 20.84 

2.25 76.1 18.8 8.3 6.46 16.20 

2.63 75.3 21.16 10 5.85 15.34 

#2 FBH, 

Phased Array 

Ti-6Al-4V 

3 57.6 14.5 8.8 8.56 18.65 

0.2 - - - 

0.48 22.4 10.2 5.7 3.71 11.39 

0.75 20.8 8.6 4.8 4.21 12.49 

1.13 32.2 11.4 5.7 4.65 13.35 

1.5 18.8 13.7 6.9 1.75 4.86 

1.87 23.5 14.9 8.6 2.37 7.48 

2.25 29 18.8 8.3 1.97 5.90 

2.63 28.2 21.16 10 1.63 4.25 

#1 FBH, 

Phased Array 

Ti-6Al-4V

3 20.8 14.5 8.8 2.11 6.47 

3-37
3.8.3 Comparison of the Three Inspection Methods. 

The results collected from inspecting the 5′′ diameter Waspaloy and Ti standards were compared 

to each other based on the SNR and the relative sensitivity of the technique. Figure 3-23(a) 

shows the results of comparing the SNR from each one of the three techniques used in the 

inspection of the 5′′ diameter Waspaloy standard for the #1 FBH at the various depths, whereas 

figure 3-23(b) shows a similar comparison for the #2 FBHs at similar depths. The sensitivity 

curves were constructed based on this data and are illustrated in figure 3-24. Figures 3-23 and 

3-24 show that the performance of the multizone and phased array inspections are almost on the 

same level and are slightly better than the conventional inspection. 

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

FBH Depth [in]

SNR [dB]

Single Transducer Multi-Zone

Phased Array Conventional

(a) #2 FBH in Waspaloy

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

FBH Depth [in]

SNR [dB]

Single Transducer Multi-Zone

Phased Array Conventional

(b) #1 FBH in Waspaloy

FIGURE 3-23. COMPARISON OF THE SNR FROM THE THREE TECHNIQUES USED IN 

INSPECTING THE 5′′ DIAMETER WASPALOY BILLET REFERENCE STANDARD 

3-38
0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.5 1 1.5 2 2.5 3 3.5

Material Depth (inches)

Sensitivity (FBH #)

Single Transducer #2 Single Transducer #1 Multi Zone #1 

Phased Array #1 Conventional #2 Conventional #1 

FIGURE 3-24. SENSITIVITY VS DEPTH AT SNR = 1.4 (3 dB) FOR THE 5′′ DIAMETER 

WASPALOY BILLET REFERENCE STANDARD 

Figure 3-25(a) shows the comparison for the SNR from each of the three techniques used in the 

inspection of the 5′′ diameter Ti standard for the #1 FBH at various depths, whereas 

figure 3-25(b) shows a similar comparison for the #2 FBHs at similar depths. The sensitivity 

curves for this case were also constructed based on SNR data and are illustrated in figure 3-26. 

As with the Waspaloy data in figure 3-24, the ST inspection sensitivity in figure 3-26 is shown as 

a series of values, one for each of the FBH depths. As with the Waspaloy evaluation, the 

sensitivity of a production conventional inspection would again be represented by a single value 

equivalent to the sensitivity at the center of the billet. In this case, the production sensitivity in 

figure 3-26 is drawn as a straight line across all depths at a value of about #2.2 FBH. This single 

sensitivity again results from the fact that the conventional beam travels throughout the entire 

billet depth when evaluating FBH at all depths. This means the noise levels (mean and peak) for 

FBH at all depths would be identical and equal to the noise values obtained when scanning the 

deepest (3′′ deep) FBH in this study. Figures 3-25 and 3-26 show that the performance of the 

multizone and phased array inspections are almost on the same level (sensitivity < #1 FBH), and 

both are much better (about six times more sensitive at the billet center) than the conventional 

inspection sensitivity that ranges between #1.5 FBH and #2 FBH. 

3-39
0.0

5.0

10.0

15.0

20.0

25.0

30.0

0.00 0.50 1.00 1.50 2.00 2.50 3.00

FBH Depth [in]

SNR [dB]

Phased Array

Multizone

(a) #1 FBH in Ti-6Al-4V

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0.00 0.50 1.00 1.50 2.00 2.50 3.00

FBH Depth [in]

SNR [dB]

Single Transducer

Phased Array

Multizone

Conventional

(b) #2 FBH in Ti-6Al-4V

FIGURE 3-25. COMPARISON OF THE SNR FROM THE THREE TECHNIQUES USED IN 

INSPECTING THE 5′′ DIAMETER Ti BILLET REFERENCE STANDARD 

3-40
0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.511.522.533

Material Depth (Inches)

Sensitivity (FBH#)..

.5

Single Transducer #2 Multi Zone #1

Phased Array #1 Conventional #2

FIGURE 3-26. SENSITIVITY VS DEPTH AT SNR = 1.4 (3 dB) FOR THE 

5′′ DIAMETER Ti BILLET REFERENCE STANDARD 

In this effort, 5′′ diameter Waspaloy and Ti-6Al-4V billet reference standards have been 

inspected using four different inspection techniques, namely, conventional, ST, multizone, and 

phased array. For both materials, note that the multizone and phased array inspections 

performed, in general, significantly better than the conventional and ST inspections. The results 

obtained in this study seem to indicate that, in general, the multizone and phased array 

inspections performed at the same level with the multizone inspection performing slightly better 

than the phased array inspection for the Waspaloy standard. Some degraded performance of the 

phased array inspection was also noticed in the near-surface zone, which can be attributed to the 

improper shape of the spherically focused center element of the probe that resulted from the 

manufacturing process. 

Note that a production setup was used for the multizone inspection for this inspection, which is 

not the case for phased array inspection. The phased array inspection is an experimental 

laboratory evaluation, which still requires some optimization. Currently, this is done 

empirically, and no systematic way exists to check the optimization. Therefore, the phased array 

data should be viewed as one set of data that was collected based on the current best knowledge 

of how to perform the inspection. Future work is needed to optimize this technique and make 

sure that the best inspection scenario is selected. Also note that for the multizone inspection, the 

amplitude of the #2 FBH indications was calculated by scaling the amplitude of the #1 FBH by 

the ratio of the attenuation set for the #1 and #2 FBHs during the calibration process. This was 

done because during collection of C-scans for the multizone inspection, the focus was on the #1 

FBHs, which resulted in all the #2 FBH indications being saturated. 

3-41/3-42
4. SUMMARY. 

The following is a summary of this study: 

• Billet converted with GFM processing is more acoustically noisy than billet converted 

using V-Die processing. GFM material was selected for use in calibration standards 

since this provides a more conservative assessment. 

• Transducer characterization procedures were developed for bicylindrically focused 

transducers, which are useful for ensuring that actual focal characteristics match the 

intended design values. 

• The Waspaloy calibration standard was more ultrasonically noisy than the IN718 material 

(75% peak noise compared to 20%, respectively) when measured with the same 

calibration target. 

• The multizone inspection procedure and transducers originally used for Ti successfully 

exceeded the program goal of #1 FBH for IN718 and #2.5 FBH for Waspaloy by 

substantial margins. The multizone system exceeded the IN718 goal by a minimum of 

3.5 times and was a minimum of 31 times more sensitive than the current conventional 

inspection requirement. Multizone exceeded the Waspaloy goal by a minimum of 4 

times and was a minimum of 14 times more sensitive than the current conventional 

inspection requirement. 

• The use of conventional transducers in the two-zone laboratory inspection nearly met the 

program goal for IN718. The laboratory conventional immersion inspection exceeded the 

program goal of #2.5 FBH sensitivity for Waspaloy in the near-surface zones. No data 

was gathered for the production conventional contact inspection of Waspaloy. 

• The factory assessment showed that the surface finish used for conventional inspection 

was adequate for the increased sensitivity of the multizone test, although the multizone 

test is more sensitive to surface blemishes. 

• The factory assessment showed comparable characteristics for inspection of Ni when 

compared to experience with inspection of Ti multizone procedures. 

• A cost comparison revealed increased investment and operational cost for multizone 

compared to conventional. The initial cost layout was $310,000 higher for the multizone 

equipment and additional yearly costs were documented. Increased operational costs 

associated with multizone inspections were documented for setup, scanning, and analysis. 

The cost of increased material due to more material being rejected could not be clearly 

ascertained. 

• Suppliers expressed concerns regarding transducer manufacturability and limited 

availability of transducer vendors. 

4-1
• The factory demo on 81,000 pounds of two and three times melted IN718 generated 

conclusive results that the multizone system can detect indications that are missed by the 

current conventional inspection. A total of 19 indications were detected by multizone, all 

of which were significantly smaller than conventional inspection requirements, which are 

at a #2 FBH sensitivity and, therefore, below the threshold for detection. 

• Conventional inspection of 5′′ diameter billet nearly met the current #2 FBH sensitivity in 

the center zone of both Ti and Waspaloy standards. However, slight modification of the 

current conventional inspection to reflect the method used for evaluating the results from 

the ST inspection showed that a significant improvement in the sensitivity could be 

achieved. 

• Multizone and phased array inspection of 5′′ diameter Waspaloy billet indicated that 

multizone achieved about a #0.5 FBH sensitivity throughout most of the billet depth 

while phased array achieved about a #0.75 FBH. The multizone inspection exceeded the 

conventional inspection sensitivity by about 20 times at the billet center. 

• Multizone and phased array inspection of 5′′ diameter Ti-6Al-4V billet indicated that 

both achieved about a #0.75 FBH sensitivity throughout the billet depth, which exceeded 

the conventional immersion sensitivity by about nine times. 

4-2
5. REFERENCES. 

1. Howard, P., Copley, D., and Gilmore, R., “Transducer Design for High Sensitivity 

Ultrasonic Inspection of Titanium,” in Review of Progress in QNDE, Vol. 16A, D.O. 

Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1997, pp. 893-900. 

2. Yalda, I., Panetta, P.D., Margetan, F.J., and Thompson, R.B., “Characterization of 

Ultrasonic Focused Transducers Using Axial Scans and C-Scans,” in Review of Progress 

in QNDE, Vol. 16A, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, 

1997, pp. 927-934. 

3. Howard, P., Copley, D., Young, J., Nieters, E., and Gilmore, R., “An Improved 

Methodology for the Inspection of Titanium Alloys,” Proceedings of the 1996 IEEE 

Ultrasonics Symposium, Vol. 1, M. Levy, S. Schneider, and B. McAvoy, eds., IEEE 

Press, 1996, pp. 727-730. 

4. Howard, P. and Gilmore, R.S., “Ultrasonic Noise and the Volume of the Ultrasonic 

Pulse,” in Review of Progress in QNDE, Vol. 15B, D.O. Thompson and D.E. Chimenti, 

eds., Plenum Press, New York, 1996, pp. 1495-1502. 

5. Howard, P., Copley, D., Nieters, E., Young, J., Keller, M., and Gilmore, R., “Ultrasonic 

Inspection of Cylindrical Titanium Billet,” presented at ASNT Fall Conference, October 

1994. 

6. Gray, T.A., “Application of Measurement Models to Specification of Ultrasonic 

Inspections,” in Review of Progress in QNDE, Vol. 16B, D.O. Thompson and D.E. 

Chimenti, eds., Plenum Press, New York, 1997, pp. 2061-2068. 

7. Thompson, R.B., “Use of UT Models in Titanium Inspection Development,” in Review of 

Progress in QNDE, Vol. 16B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, 

New York, 1997, pp. 1537-1545. 

8. Thompson, R.B., “A Generalized Model of the Effects of Microstructure on Ultrasonic 

Backscattering and Flaw Detection,” in Review of Progress in QNDE, Vol. 15B, D.O. 

Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1996, pp. 1471-1477. 

9. Yalda, I., Margetan, F.J., Han, K.Y., and Thompson, R.B., “Survey of Ultrasonic Grain 

Noise Characteristics in Jet Engine Titanium,” in Review of Progress in QNDE, Vol. 

15B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1996, pp. 1487-

1494. 

10. Han, K.Y. and Thompson, R.B., “Relationship Between the Two-Point Correlation of 

Elastic Constants and Backscattered Ultrasonic Noise in Two-Phase Titanium Alloys,” in 

Review of Progress in QNDE, Vol. 14A, D.O. Thompson and D.E. Chimenti, eds., 

Plenum Press, New York, 1995, pp. 67-74. 

5-1
11. Margetan, F.J., Han, K.Y., Yalda, I., Goettsch, S., and Thompson, R.B., “The Practical 

Application of Grain Noise Models in Titanium Billets and Forgings,” in Review of 

Progress in QNDE, Vol. 14B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, 

New York, 1995, pp. 2129-2136. 

12. Panetta, P.D., Margetan, F.J., Yalda, I., and Thompson, R.B., “Ultrasonic Attenuation 

Measurements in Jet-Engine Titanium Alloys,” in Review of Progress in QNDE, Vol. 

15B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1996, pp. 1525-

1532. 

13. Margetan, F.J., Panetta, P.D., and Thompson, R.B., “Ultrasonic Signal Attenuation in 

Engine Titanium Alloys,” in Review of Progress in QNDE, Vol. 17B, D.O. Thompson 

and D.E. Chimenti, eds., Plenum Press, New York, 1998, pp. 1469-1476. 

14. Panetta, P.D., Thompson, R.B., and Margetan, F.J., “Use of Electron Backscatter 

Diffraction in Understanding Texture and the Mechanisms of Backscattered Noise 

Generation in Titanium Alloys,” in Review of Progress in QNDE, Vol. 17A, D.O. 

Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1998, pp. 89-96. 

15. Thompson, R.B., Margetan, F.J., Yalda, I., Chiou, C.-P., and Panetta, P.D., “Coupling 

Microstructure Outputs of Process Models to Ultrasonic Inspectability Predictions,” in 

Review of Progress in QNDE, Vol. 17B, D.O. Thompson and D.E. Chimenti, eds., 

Plenum Press, New York, 1998, pp. 1847-1853. 

16. Thompson, R.B., Panetta, P.D., and Margetan, F.J., “Relationship of the Ultrasonic 

Backscattering Coefficient of Titanium Alloys to Microstructure,” in Materials and 

Processes Affordability: Keys to the Future, H.S. Kliger, B.J. Rasmussen, L.A. Pilato, 

and T.B. Tolle, eds., SAMPE, Covina, CA, 1998, pp. 1448-1457. 

17. Margetan, F.J., Yalda, I., and Thompson, R.B., “Predicting Gated-Peak Grain Noise 

Distributions for Ultrasonic Inspections of Metals,” in Review of Progress in QNDE, Vol. 

15B, D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1996, pp. 1509-

1516. 

18. Panetta, P.D., Margetan, F.J., Yalda, I., and Thompson, R.B., “Observation and 

Interpretation of Microstructurally Induced Fluctuations of Back-Surface Signals and 

Ultrasonic Attenuation in Titanium Alloys,” in Review of Progress in QNDE, Vol. 16B, 

D.O. Thompson and D.E. Chimenti, eds., Plenum Press, New York, 1997, pp. 1547-1554. 

19. Margetan, F.J., Gigliotti, M., Brasche, L., and Leach, W., “Fundamental Studies: 

Inspection Properties for Engine Titanium Alloys,” FAA Report DOT/FAA/AR-02/114, 

December 2002. 

20. Brasche, L., Chiou, T., Thompson, R.B., Smith, K., Meeker, B., Margetan, F., Panetta, P., 

Chenail, R., Galli, F., Umbach, J., Raulerson, D., Degtyar, A., Bartos, J., Copley, D., 

5-2
McElligott, B., Howard, P., and Bashyam, M., “Contaminated Billet Study,” FAA report 

DOT/FAA/AR-05/16, September 2005. 

21. Umbach, J.A. and Roberts, R.A., “Ultrasonic Phased Array Transducers-Model and 

Experiment,” presented at ASNT Fall Conference, October 1997. 

22. Margetan, F., Nieters, E., Haldipur, P., Brasche, L., Chiou, T., Keller, M., Degtyar, A., 

Umbach, J., Hassan, W., Patton, T., and Smith, K., “Fundamental Studies of Nickel Billet 

Materials—Engine Titanium Consortium II,” FAA report, DOT/FAA/AR-05/17, June 

2005. 

23. Roberts, R.A., “Phased Array Beam Modeling Using a Discretely Orthogonal Gaussian 

Aperture Basis,” in Review of Progress in QNDE, Vol. 23, D.O. Thompson and D.E. 

Chimenti, eds., American Institute of Physics, Melville, NY, 2004. 

24. Keller, M., Patton, T., Degtyar, A., Umbach, J., Hassan, W., Kinney, A., Roberts, R., 

Margetan, F., and Brasche, L., “Inspection Development for Titanium Billet—Engine 

Titanium Consortium Phase II,” FAA report, DOT/FAA/AR-05/30, September 2005. 

25. Hassan, W., “Evaluation of Multizone Inspection Variability at the Supply Base for 8-

Inch-Diameter Ti-6Al-4V: A Round-Robin Study,” in Review of Progress in QNDE, Vol. 

22B, D.O. Thompson and D.E. Chimenti, eds., American Institute of Physics, Melville, 

NY, 2003, pp. 1870-1877. 

5-3/5-4
APPENDIX A—DEFECT CHARACTERIZATION OF NATURALLY

OCCURRING ANOMALIES

Four indications were ultrasonically and metallographically characterized. Samples were 

ultrasonically characterized at ISU and metallographically characterized by the OEM members 

of ETC. The results of the characterization are provided in appendix A. Details of the ultrasonic 

characterization procedure are provided in appendix B. A summary of the anomaly 

characterization is provided in table A-1. 

TABLE A-1. ANOMALY CHARACTERIZATION DATA SUMMARY. 

Indication 

Number Material Description 

Ultrasonic Response 

(% Full) 

Screen Height Anomaly Type 

1 IN718 VIM/ESR/VAR 22.5 Crack 

2 IN718 VIM/ESR/VAR 33.6 Melt-related slag inclusion 

high in oxygen 

3 IN718 VIM/VAR 44.0 Entrapped slag 

4 IN719 VIM/VAR 20.5 Entrapped slag 

A-1
Ni Billet Indication #1 – General Information

• Alloy Inconel 718

• Melt method triple melt 

VIM/ESR/VAR

• Billet diameter 10 inch

• Size of calibration reflector (1/64ths of inch) #1

• Calibration amplitude (% screen height) 80%

• Indication amplitude before evaluation (% screen height) 22.5%

• Indication amplitude after evaluation (% screen height) 22.5%

• Distance Amplitude Correction (DAC) No

• Indication Depth 4.4 inches

• Indication Length 0.75 inches

• Transducer information:

– Frequency 5 MHz

– Transducer Element 2.0 inches circular

– Focal length 7.7 & 19.8 inches

– Lens curvature bi-cylindrical

– Beam diameter 0.245” axial

– Test mode longitudinal

– Water Path 3.0 inches

Ni Billet Indication # 1 – composite micrograph

• Based on multizone UT data, the 

indication was believed to be 50 

mils deep from side #2. After 

metallographic examination, the 

indication appears to have been 

around a depth of 30 mils. When 

the indication was revealed at 30 

mils, the decision was made not to 

use the microprobe to obtain the 

composition of the indication since 

it was thought that indication was at 

a depth of 50 mils. There was no 

indication revealed at depths of 52 

mils and 57 mils. Therefore, no 

microprobe results were obtained 

on this indication. 

• Maximum Indication Size:

– 12.5 mil axial length (Distance 

along crack length)

– 1.2 mil radial length (Distance 

across crack length)

– 6 mils in depth (Length 

determined from assuming 

indication present half way 

between step polishes in which 

indication was revealed and not 

revealed)

Side #1

Side #3

Side #6 Side #5

NOTE: Polished surface is Side #2 

& indication was in between three 

EDM plunged holes

Side #2

A-2
Depth = 10 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

Depth = 20 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

Depth = 30 mils

25X

50X

20 mils

10 mils 12.5 mils

1.2 mils

Ni Billet Indication # 1 – composite micrograph

A-3
Depth = 32 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

Depth = 37 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

Depth = 42 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

A-4
Depth = 47 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

Depth = 52 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

Depth = 57 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 1 – composite micrograph

A-5
Billet Information

 Found in 10" triple melt Inconel 718 billet

Cube Information

 Dimension: sides 1&3 - 25.70mm, sides 2&4 - 25.23mm and sides 5 &6 - 25.37mm

 UT scans were performed at ISU using a Utex WinSpect system.

 UT data include single a-scans at peak positions, c-scan images, and volumetric ascans at c-scan scan grids using 5 and 50 MHz transducers.

 Additional a-scans were obtained from fused quartz block as reference waveforms.

 Indication signals can only be identified on sides 1 and 3. 

Billet/Cube Orientation

1

5 Billet axis

4

UT beam direction 2

3

6 1

5 Billet axis

4

UT beam direction 2

3

6

Ni Billet Indication # 1 – Ultrasonic Measurements

Scan Parameters

250 MHz sampling rate and 61 x 61 pixels 

(scan positions) at 5 mils spatial increment 

applied to all scans. 

PH scans used 4 time averages and 0.5ms 

time gates. 

P6 scans used 16 time averages and 1.37 

and 0.78 ms time gates for sides 1 and 3, 

respectively.

A-6
P6 (5MHz) C-scan Images

5 5 6 6

Side 1

Gain=37dB

Side 3

Gain=46 dB

4 2

4 2

Multizone Color Code

0 128 255=1v

Ni Billet Indication # 1 – Ultrasonic Measurements

PH (50MHz) C-scan Images

5 6 5 6

Side 1

Gain=39dB

Side 3

Gain=47 dB

2

2

4

4

Multizone Color Code

0 128 255=1v

A-7
Ni Billet Indication #2 – General Information

• Alloy Inconel 718

• Melt method Triple melt 

VIM/ESR/VAR

• Billet diameter 10 inch

• Size of calibration reflector (1/64ths of inch) #1

• Calibration amplitude (% screen height) 80%

• Indication amplitude before evaluation (% screen height) 33.6%

• Indication amplitude after evaluation (% screen height) 33.6%

• Distance Amplitude Correction (DAC) No

• Indication Depth 4.375 inches

• Indication Length 0.75 inches

• Transducer information:

• Frequency 5 MHz

• Transducer Element 2.0 inches circular

– Focal length 7.7 & 19.8 inches

– Lens curvature bi-cylindrical

– Beam diameter 0.245” axial

– Test mode longitudinal

– Water Path 3.0 inches

Ni Billet Indication # 2 – composite micrograph

• Based on multizone UT data, 

the indication was believed to 

be 50 mils deep from side #2. 

After metallographic 

examination, the indication was 

revealed at a depth of 50 mils. 

When the indication was 

revealed at 50 mils, the decision 

was made to use the 

microprobe to obtain the 

composition of the indication. 

There was no diffusion zone 

around the indication. 

Indication was believed to be 

melt related (slag) defect based 

on chemical analysis.

• Maximum Indication Size:

– 26.7 mil axial length

– 0.4 mil radial length

– 9.5 mils in depth (Length 

determined from assuming 

indication present half way 

between step polishes in which 

indication was revealed and not 

revealed)

Side #1

Side #3

Side #6 Side #5

NOTE: Polished surface is Side #2 & 

indication was in between three EDM 

plunged holes

Side #2

A-8
Depth = 10 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

Depth = 20 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

Depth = 30 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

A-9
Depth = 35 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

Depth = 40 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

Depth = 45 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

A-10
Depth = 50 mils

13.3 mils

0.6 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0 20 40 60 80 100

Position (microns)

Element Weight % (wt. %)

Ni

Cr

Fe

Nb

Mo

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 20 40 60 80 100

Position (microns)

Element Weight % (wt. %)

Ti

Al

Mg

Ca

Si

Cl

Ni Billet Indication # 2 – SEM analysis – 50 mil slice

A-11
•Oxygen is present in abundance in indication.

•Not clear if Nitrogen is present in indication

•Could be just Titanium or Titanium and Nitrogen

Oxygen Titanium

Boron Carbon Nitrogen & Titanium

Ni Billet Indication # 2 – SEM analysis – 50 mil slice

Step Scan Through Defect (5x5um rasters)

Pt# um Ni Cr Fe Ti Mo Nb Al Mn V W Zr S Mg Ca Na Si Cl

1 0 53.75 18.16 18.00 0.93 3.32 5.51 0.46 0.03 0.03 0.00 0.08 0.08 0.00 0.01 0.11 0.07 0.03

2 5 53.96 18.22 17.98 1.01 3.34 5.50 0.44 0.11 0.00 0.01 0.00 0.05 0.00 0.00 0.00 0.08 0.02

3 10 54.35 18.09 18.10 0.99 2.89 5.45 0.46 0.05 0.02 0.00 0.00 0.09 0.01 0.00 0.03 0.05 0.03

4 15 53.46 18.14 18.07 0.96 3.07 5.21 0.46 0.10 0.00 0.05 0.03 0.10 0.02 0.00 0.00 0.05 0.00

5 20 53.54 18.13 17.92 0.95 2.99 5.44 0.46 0.07 0.03 0.03 0.00 0.14 0.00 0.00 0.07 0.05 0.01

6 25 53.33 18.05 17.85 0.99 3.15 5.38 0.43 0.07 0.01 0.00 0.09 0.03 0.05 0.01 0.08 0.05 0.00

7 30 53.77 18.18 18.02 0.99 3.33 5.46 0.49 0.07 0.01 0.00 0.03 0.04 0.00 0.00 0.15 0.04 0.03

8 35 53.25 18.10 17.99 0.99 3.14 5.37 0.46 0.06 0.03 0.00 0.00 0.02 0.00 0.01 0.00 0.08 0.00

9 40 53.61 18.01 18.00 0.97 3.23 5.33 0.46 0.08 0.01 0.00 0.03 0.07 0.00 0.00 0.08 0.05 0.01

10 45 51.33 17.74 17.42 1.47 2.96 5.44 0.97 0.08 0.03 0.00 0.00 0.05 0.27 0.02 0.10 0.24 0.06

11 50 23.48 8.39 7.81 9.33 1.19 3.98 13.10 0.04 0.04 0.00 0.11 0.23 5.62 0.85 0.25 1.53 0.16

12 55 36.62 13.02 12.75 6.06 1.86 4.00 8.06 0.05 0.00 0.00 0.00 0.12 2.14 0.22 0.08 1.21 0.13

13 60 41.34 14.49 14.41 6.29 2.56 4.60 7.91 0.10 0.05 0.00 0.00 0.07 4.78 0.19 0.15 0.22 0.04

14 65 53.39 18.17 18.07 1.02 3.20 5.25 0.44 0.08 0.04 0.00 0.29 0.04 0.00 0.01 0.07 0.03 0.04

15 70 53.06 18.07 17.92 0.99 3.01 5.31 0.43 0.05 0.02 0.00 0.00 0.03 0.00 0.01 0.01 0.02 0.02

16 75 53.01 18.29 17.99 1.00 3.41 5.21 0.44 0.09 0.01 0.00 0.13 0.03 0.00 0.00 0.10 0.07 0.01

17 80 53.43 18.13 17.99 0.98 3.00 5.26 0.49 0.06 0.00 0.00 0.00 0.11 0.00 0.01 0.00 0.09 0.03

18 85 53.64 18.42 18.06 0.99 3.12 5.41 0.44 0.04 0.00 0.00 0.00 0.11 0.00 0.00 0.00 0.06 0.02

19 90 53.58 18.07 17.86 1.00 3.05 5.49 0.44 0.04 0.03 0.02 0.00 0.03 0.00 0.00 0.22 0.07 0.02

20 95 53.66 18.06 17.95 0.98 2.84 5.41 0.46 0.06 0.01 0.00 0.00 0.13 0.00 0.00 0.03 0.05 0.00

21 100 53.31 17.91 17.89 1.00 2.82 5.43 0.44 0.10 0.00 0.00 0.00 0.10 0.00 0.00 0.17 0.06 0.08

Ni Billet Indication # 2 – SEM analysis – 50 mil slice

A-12
Depth = 52 mils

25X

50X

20 mils

10 mils

26.7 mils

0.4 mils

Ni Billet Indication # 2 – composite micrograph

Depth = 54 mils

25X

50X

20 mils

10 mils

26.7 mils

0.4 mils

Ni Billet Indication # 2 – composite micrograph

Depth = 56 mils

25X

50X

20 mils

10 mils

0.4 mils

2.9 mils

Ni Billet Indication # 2 – composite micrograph

A-13
Depth = 58 mils

25X

50X

20 mils

10 mils

Ni Billet Indication # 2 – composite micrograph

Billet Information

 Found in 10" triple melt Inconel 718 billet 

Cube Information

 Dimension: sides 1&3-26.39mm, sides 2&4-26.83mm and sides5 &6-25.97mm. 

 UT scans were performed at ISU using a Utex WinSpect system.

 UT data include single A-scans at peak positions, C-scan images, and volumetric Ascans at C-scan scan grids using 5 and 50 MHz transducers.

 Additional A-scans were obtained from fused quartz block as reference waveforms.

 Indication signals can only be identified on sides 1 and 3. 

Billet/Cube Orientation

TS1Top, 1

F, 6 Billet axis

R, 4

UT beam direction L,2

Bot, 3

Back, 5 TS1Top, 1

F, 6 Billet axis

R, 4

UT beam direction L,2

Bot, 3

Back, 5

Ni Billet Indication # 2 – Ultrasonic Measurements

Scan Parameters

250 MHz sampling rate, 16 time 

averages and 61x61 pixels (scan 

positions) at 5 mils spatial increment 

applied to all scans. 

PH scans used 0.69 ms time gates. 

P6 scans used 0.49 and 1 ms time 

gates for sides 1 and 3, respectively.

A-14
P6 (5MHz) C-scan Images

5 6 5 6

Side 1

Gain=48dB

Side 3

Gain=53 dB

2 4

4 2

Multizone Color Code

0 128 255=1v

Ni Billet Indication # 2 – Ultrasonic Measurements

PH (50MHz) C-scan Images

5 6 5 6

Side 1

Gain=50dB

Side 3

Gain=54dB

2

2

4

4

Multizone Color Code

0 128 255=1v

PH (50MHz) C-scan Images

5 6 5 6

Side 1

Gain=50dB

Side 3

Gain=54dB

2

2

4

4

Multizone Color Code

0 128 255=1v

A-15
Ni Billet Indication #3 – General Information

• Billet: double melt 718, 10” diameter

• MZ Calibration: #1 flat-bottom hole at 80% of full screen height

• MZ Indication Amplitude: 44% of full screen height (zone 2)

• MZ Depth: 5.2”

• MZ Length: 0.45”

• MZ Transducer Information:

– Frequency 5 MHz

– Transducer Element 1.25 inches circular

– Focal length 6.0 & 8.6 inches

– Lens curvature bi-cylindrical

– Beam diameter 0.245” axial

– Test mode longitudinal

– Water Path 3.0 inches

• Conv Calibration: #2 flat-bottom hole

• Conv Indication Amplitude: 15%

• Conv Depth: 4.8”

• Conv Length: 0.125”

Ni Billet Indication # 3 – sample sectioning convention

Top=1

Billet axis Front=6

Right=4

Left=2 UT beam direction

BOT=3

Back=5

Top=1

Billet axis Front=6

Right=4

Left=2 UT beam direction

BOT=3

Back=5

A-16
Ni Billet Indication # 3 – composite micrograph

Polish 1

Polish 2

Ni Billet Indication # 3 – composite micrograph

Polish 3

Ni Billet Indication # 3 – composite micrograph

A-17
Polish 4

Ni Billet Indication # 3 – composite micrograph

Polish 5

Ni Billet Indication # 3 – composite micrograph

Polish 6

Ni Billet Indication # 3 – composite micrograph

A-18
Ni Billet Indication # 3 – SEM analysis 

Flaw approximately 0.015” as it appeared after removal of 0.052” of 

material

 

A-19
Ni Billet Indication # 3 – SEM analysis

Flaw approximately 0.015” as it appeared after removal of 0.052” of 

material

XES analysis of material in the flaw area showed the presence of primarily nickel, 

chromium, iron, niobium, molybdenum, titanium, aluminum and magnesium.

A-20
Ni Billet Indication # 3 – SEM analysis 

Flaw approximately 0.015” as it appeared after removal of 0.052” of 

material

Spot XES analysis within the flaw (location 1 above) showed the presence of 

primarily aluminum, magnesium and oxygen.

A-21
Spot XES analysis within a basemetal area near the flaw (location 3,

previous page) verified the surrounding material composition is consistent 

with IN718.

Ni Billet Indication # 3 – SEM analysis 

Flaw approximately 0.015” as it appeared after removal of 0.052” of 

material

XES elemental maps showing the concentration of 

specific elements within a portion of the flaw are 

found on subsequent pages.

A-22
Ni Billet Indication # 3 – SEM analysis

A-23
Ni Billet Indication # 3 – Ultrasonic Measurements

Side 2 15 MHz Side 4

Image resolution: All are of 0.005” scan increment (in-between pixels)

Orientation: side 5 on left and side 6 on right for sides 1~4; side 2 on left and side 4 on right for sides 5~6;

both images centered w.r.t. cube face

0.8” X 0.8”

Gain=40 dB Multizone Color Code

0 128 255

Experimental C-scan Images

0.5” X 0.5”

Gain=43 dB

50 MHz

Side 1 Side 3

0.3” X 0.3”

Gain=41 dB

1.0” X 1.0”

Gain=36 dB

air bubble 

on surface

Image resolution: 0.002” scan increment (in-between 

pixels)

Orientation: side 5 on left and side 6 on right; both images 

centered w.r.t. cube face

Multizone Color Code

0 128 255

5 MHz Side 1 Side 2 Side 3 Side 4

Image resolution: All are 0.8” by 0.8” centered; of 0.01” scan increment (in-between pixels)

Orientation: side 5 on left and side 6 on right ; all images centered w.r.t. cube face

Multizone Color Code

0 128 255

Gain=47 dB Gain=52 dB Gain=46 dB Gain=55 dB

A-24
Ni Billet Indication #4 – General Information

• Alloy Inconel 718

• Melt method Double melt 

VIM/VAR

• Billet diameter 10 inch

• Size of calibration reflector (1/64ths of inch) #1

• Calibration amplitude (% screen height) 80%

• Indication amplitude before evaluation (% screen height) 20.5% 

• Indication amplitude after evaluation (% screen height) 20.5%

• Distance Amplitude Correction (DAC) No

• Indication Depth 1.7 inches

• Indication Length 0.18 inches

• Transducer information:

– Frequency 5 MHz

– Transducer Element 1.5 inches circular

– Focal length 7.0 & 13.7 inches

– Lens curvature bi-cylindrical

– Beam diameter 0.245” axial

– Test mode longitudinal

– Water Path 3.0 inches

Ni Billet Indication # 4 – Cube orientation naming system

Top=1

Billet axis Front=6

Right=4

Left=2 UT beam direction

BOT=3

Back=5

Top=1

Billet axis Front=6

Right=4

Left=2 UT beam direction

BOT=3

Back=5

A-25
Ni Billet Indication # 4 – composite micrograph

Depth = 40 mils

Depth = Distance From Original Surface of Side #2

Axial Measurement = Distance along crack length (27.6 Mils)

25X 50X

Ni Billet Indication # 4 – SEM results from slice 1 and depth of 40 mils

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0 20 40 60 80 100 120

Position (um)

Elemental Weight %

Ni

Cr

Fe

Nb

Mo

S

0.00

10.00

20.00

30.00

40.00

50.00

0 20 40 60 80 100 120

Position (um)

Elemental Weight %

Ti

Al

Mg

Ca

Si

Cl

A-26
Microprobe Dot Maps

•Oxygen is present in 

abundance.

•Not clear if Nitrogen is 

present

•Could be just Titanium 

or, Titanium and 

Nitrogen

Oxygen Titanium

Carbon Nitrogen & Titanium

Ni Billet Indication # 4 – SEM results from slice 1 and depth of 40 mils

Ni Billet Indication # 4 – SEM results from slice 7 and depth of 50 mils

Microprobe data

Step Scan Through Defect (5x5um rasters)

Pt# um Ni Cr Fe Ti Mo Nb Al Mn V W Zr S Mg Ca Na Si Cl Total

1 0 53.29 17.78 17.69 0.98 2.97 5.53 0.46 0.05 0.04 0.01 0.14 0.01 0.02 0.00 0.00 0.09 0.06 99.13

2 5 53.81 17.74 17.93 0.97 3.20 5.48 0.49 0.06 0.06 0.00 0.09 0.08 0.00 0.02 0.00 0.08 0.02 100.04

3 10 53.25 17.71 17.92 0.98 3.01 5.37 0.47 0.07 0.05 0.00 0.04 0.13 0.00 0.00 0.00 0.06 0.05 99.11

4 15 53.65 17.89 17.83 1.00 3.11 5.33 0.43 0.06 0.06 0.00 0.00 0.16 0.04 0.00 0.02 0.11 0.01 99.72

5 20 53.39 17.72 17.74 1.04 2.59 5.52 0.48 0.05 0.03 0.00 0.00 0.10 0.00 0.00 0.01 0.04 0.05 98.76

6 25 52.58 17.67 17.82 0.99 2.83 5.54 0.48 0.04 0.02 0.00 0.18 0.03 0.01 0.00 0.00 0.03 0.03 98.27

7 30 52.06 17.64 17.99 1.00 2.82 5.42 0.48 0.05 0.03 0.00 0.20 0.07 0.00 0.00 0.00 0.05 0.03 97.84

8 35 52.11 17.73 17.65 1.00 3.16 5.72 0.46 0.09 0.03 0.00 0.15 0.08 0.01 0.01 0.00 0.09 0.05 98.31

9 40 51.41 17.92 17.87 1.04 2.90 5.34 0.50 0.04 0.03 0.00 0.00 0.10 0.00 0.00 0.01 0.08 0.08 97.32

10 45 51.70 18.04 17.72 1.08 3.01 5.54 0.49 0.06 0.05 0.00 0.00 0.08 0.03 0.01 0.00 0.05 0.06 97.91

11 50 44.37 15.44 14.68 5.24 2.73 5.57 0.71 0.06 0.03 0.00 0.00 0.36 0.12 0.13 0.08 0.23 0.29 90.04

12 55 21.33 8.40 7.97 32.56 1.10 5.42 2.35 0.02 0.12 0.00 0.15 0.26 0.58 0.81 0.02 0.20 0.32 81.60

13 60 20.46 8.02 7.55 38.76 1.18 5.34 0.76 0.00 0.15 0.00 0.00 0.10 0.04 0.25 0.01 0.06 0.33 83.02

14 65 14.84 5.99 5.47 13.56 0.97 3.90 19.97 0.01 0.05 0.00 0.00 0.14 6.50 1.18 0.03 0.69 1.81 75.10

15 70 18.86 7.32 6.77 7.47 1.07 3.92 17.38 0.01 0.04 0.00 0.06 0.16 8.01 0.70 0.02 0.80 2.10 74.67

16 75 48.86 16.72 16.51 3.01 2.82 6.71 0.62 0.06 0.04 0.02 0.15 0.18 0.38 0.05 0.07 0.09 0.14 96.45

17 80 51.95 17.98 17.84 1.04 2.98 5.50 0.51 0.03 0.06 0.00 0.00 0.06 0.05 0.01 0.05 0.09 0.08 98.22

18 85 52.15 17.90 17.64 0.99 2.95 5.47 0.47 0.04 0.04 0.00 0.15 0.05 0.02 0.00 0.01 0.07 0.02 97.98

19 90 52.32 17.82 17.86 1.01 3.07 5.76 0.49 0.03 0.07 0.00 0.01 0.04 0.00 0.01 0.04 0.05 0.03 98.62

20 95 52.75 17.90 17.65 0.98 2.66 5.46 0.49 0.06 0.00 0.00 0.20 0.09 0.03 0.00 0.00 0.10 0.09 98.48

21 100 52.62 17.94 17.72 1.00 2.92 5.58 0.47 0.05 0.05 0.00 0.16 0.08 0.00 0.00 0.00 0.11 0.06 98.76

22 105 52.67 18.03 17.59 1.02 3.03 5.37 0.49 0.08 0.05 0.00 0.06 0.08 0.00 0.00 0.00 0.07 0.03 98.56

23 110 52.62 17.82 17.27 1.00 3.05 5.82 0.47 0.06 0.03 0.00 0.00 0.05 0.01 0.00 0.00 0.07 0.01 98.28

24 115 52.11 17.83 17.63 1.00 2.74 5.44 0.47 0.09 0.03 0.00 0.00 0.01 0.00 0.00 0.01 0.05 0.02 97.43

25 120 51.62 17.45 18.07 1.01 3.14 5.22 0.48 0.04 0.05 0.01 0.00 0.06 0.03 0.00 0.02 0.09 0.01 97.29

(Step Scan through 120um 

using 5x5 rasters)

A-27
Ni Billet Indication # 4 – composite micrograph

Depth = 41.6 mils

25X 50X

Ni Billet Indication # 4 – composite micrograph

Depth = 43.6 mils

25X 50X

A-28
Ni Billet Indication # 4 – composite micrograph

Depth = 43.6 mils – appearance of second discontinuity

25X

50X

Ni Billet Indication # 4 – composite micrograph

Depth = 45.6 mils – appearance of third discontinuity

25X

50X

Large indication is 

beginning to break up

3rd

A-29
Ni Billet Indication # 4 – composite micrograph

Depth = 47.6 mils

25X 50X

Ni Billet Indication # 4 – composite micrograph

Depth = 49.6 mils – appearance of fourth discontinuity

25X 50X

500x

Sample was unetched because of 

the number of surface scratches. 

More material would have to be 

polished in order to etch.

A-30
Side 1 Side 2 5 MHz Side 3 Side 4

Image size: 5MHz=0.8” by 0.8”; 15MHz=0.8” by 0.8” (sides 1 and 2), 1” by 1” (the rest)

Image resolution: 5MHz=0.01”, 15MHz=0.005”

Orientation: side 5 on left and side 6 on right for sides 1~4; side 2 on left and side 4 on right for sides 5~6

NOTE: (1) Each image is roughly centered at the corresponding cube face 

(2) flaw depth is approximated by using time-of-flight of main flaw signal and measured Ni L-wave speed 

Gain=57 dB Gain=52 dB Gain=57 dB

Gain=37 dB

Flaw depth~1.18cm

Multizone Color Code

0 128 255

C-scan Images

15 MHz

Side 1 Side 2 Side 3 Side 4 Side 5

Surface 

air 

bubble

Surface 

air 

bubble

Gain=34 dB

Flaw depth~1.42cm

Gain=28 dB

Flaw depth~1.29cm

Gain=38 dB

Flaw depth~1.20cm ?

Gain=37 dB

Ni Billet Indication # 4 – Ultrasonic Measurements

50 MHz side 1

1.1” X 1.1”@0.002” (centered at cube face)

Time gate: (1.48,4.25) μs after front surface echo

Gain=28 dB

0.3” X 0.3”@0.002” (centered at cube face)

Time gate: (3.53,5.3) μs after front surface echo

Gain=31 dB

Scan #1

Scan #2

?

Ni Billet Indication # 4 – Ultrasonic Measurements

A-31
50 MHz side 2

Scan #1 Scan #2

1.1” X 1.1”@0.002” (centered at cube face)

Gain=23 dB

0.9” X 0.9”@0.002” (centered at cube face)

Gain=34 dB

Two flaw depths: ~0.835 cm and ~0.785cm

Ni Billet Indication #4 – Ultrasonic Measurements

50 MHz side 3

0.3” X 0.3”@0.002” (centered at cube face with ~0.1” offset toward lower-left corner)

Gain=38 dB

A-32
APPENDIX B—DATA ACQUISITION PROCEDURE

UT Data Acquisition Procedure for ETC Real Defects 

Using a Sonix Immersion System 

by C. Thomas Chiou, Mike Keller, Jeff Umbach and Andrei Degtyar 

Last update: 04-17-01 

1. Introduction 

This procedure is written for internal use in ETC-II Task 1.1.1 Fundamental Studies and 

other related tasks. The objective is to acquire UT A-scan, C-scan and multiple b-scan 

(volumetric A-scan) data of naturally occurring defects embedded in a small Ti- or Ni-based 

cube block. The target readers are NDE staff with sufficient experience in use of a Sonix 

immersion system. Some technical details has been included here in an attempt to make this 

document self-contained. Section 2 lists the basic requirements of system components and 

accessories. Section 3 lays out the experimental setups of the reference and defect data 

acquisition, for which the step-by-step procedures are described in Sections 6 and 7. Other 

supporting materials are provided in the remaining sections. For clarification of several key 

terminologies, the readers are referred to Section 9. 

2. System Requirements 

The designated scan hardware is a computerized Sonix immersion scan system produced in 

the 1990’s (or later) with three-axis scan capability, controlled by Sonix FlexSCAN-C 

software version 4.0 (or higher). Sonix default pulser/receiver such as DPR-35+ should be 

used if equipped, but other typical pulser/receivers such as Panametrics 505x series can be 

substituted. A standard transducer search tube (mounting pole) and a mechanical transducer 

manipulator capable of two angular position controls are assumed to be parts of the scan 

system. The defect specimen should have been sectioned down to a minimum size (typically 

around 1′′ cube) with the defect centered in the block. Knowledge of defect depth on each of 

the six sides is expected. The front and back surfaces of the defect cube block in the three 

orthogonal directions should also be made as parallel as possible. The accessories include a 

sample stand, a thermometer, transducer sets and fused-quartz reference sets. The 

specifications and usage of each accessory component are as follows. 

2.1 Sample stand 

A three- or four-legged flat stand of circular (or rectangular) shape with minimal size of 4′′

diameter (or side) is needed to support the cube sample and the reference plate in the scan 

tank. This stand should be made of rust-free materials such as stainless steel, Ti or epoxy 

glass, and the stand legs must be adjustable with good precision for leveling. 

B-1
2.2 Thermometer 

A thermometer is needed to measure the water temperature of the scan tank from which the 

water attenuation can be estimated. The precision of the thermometer should be within 1 

degree Celsius or Fahrenheit. 

2.3 Transducer Set 

Minimally, two focused transducers are needed to acquire the UT data. Both should 

generally be spherically focused with central frequencies around 5MHz for one and at least 

15 MHz for the other. Assuming a maximum 0.5′′ defect depth below all six sides of the 

defect cube block, all transducers must have at least a 2′′ true focal length (see Section 9.1 for 

definition) for good focusing. The size and focal length combination of the transducer 

should be carefully selected so that the beam entry area will not be larger than the 1′′ square 

surface of the defect cube block. The typical transducer set used consisted of a 5MHz, 1′′

diameter, 8′′ true focal length transducer and a 25 MHz, 0.25′′ diameter, 2′′ true focal length 

transducer. 

In order to determine the key transducer parameters such as the true focal lengths, geometric 

focal lengths and equivalent diameters (Section 9.1), all transducers must also be 

characterized. The transducer characterization task may be performed at ISU before a 

procedure is specified and tested at other sites in the future. 

2.4 Reference Set 

Minimally one (two recommended) fused-quartz plate is needed for the above-mentioned 

transducers to take reference waveforms (A-scans). These reference waveforms will be used 

by UT models to estimate the system efficiency factor of the scan system (Section 3.1). The 

plate thickness should be 1′′ (used with 5MHz transducer) and 0.5′′ (used with 15 MHz 

transducer and above) for the primary and the second optional plates, respectively. The size 

of the plate(s), normally 2′′-4′′ in diameter (or per side), should fit with the service area of the 

sample stand. Like the defect cube block, the front and back surfaces of the plate(s) should 

also be parallel. 

3. Experimental Setups 

3.1 Basic Setups 

One of the objectives of acquiring UT data with this procedure is to support UT modeling 

activities. The UT models used in ETC are based on ISU’s Thompson-Gray measurement 

model framework [1]. In order to predict real defect signals at absolute levels as seen on the 

oscilloscope, these UT models require a separate reference experiment from which the scan 

system response or system efficiency factor can be estimated. Thus, the data acquisition 

actually consists of two parts: the main task is to acquire the defect data from the cube block, 

and the other is to obtain the reference waveforms from, as mentioned in Section 2.4 above, 

B-2
the fused-quartz set(s). The setup of these two experiments, both in immersion mode, are 

illustrated below. 

In Figure 3.1, a focused transducer (specified in Section 2.3) is normalized (Section 3.4) to 

the front surface of a fused-quartz plate of thickness Yr,s. Given the UT speeds in water and 

fused-quartz (Sections 9.2 and 9.3), plate thickness, and the transducer focal length, the water 

path is set (see Section 9.4 for formula) to Yr,w such that the geometric focal length (section 

9.1) is on the back surface of the fused-quartz plate. Echoes from the back surface, i.e. the 

reference waveforms (A-scans), are to be acquired in this experiment. Note that additional 

spacers need to be placed between the fused-quartz plate and the stand, which ensures water 

to be the backing medium. This is important for UT models to set up correct interface 

parameters without ambiguity. 

In Figure 3.2, the same transducer is similarly normalized to the front surface of the defect 

cube block. However, a different water path Yd,w is used so that true focal length is on the 

nearest (front) surface of the defect, for which the defect depths Yd,s in all six sides should 

have been measured (Section 1). Prior to transducer normalization, the stand needs to be 

leveled with respect to the paths of the scan bridge (Section 3.2). It is also assumed that both 

front and back surfaces of the defect block are in parallel to the leveled stand surface (Section 

1). In this experiment, single-shot A-scans, two-dimensional C-scans, and three-dimensional 

b-scans (see Section 9.1 for definition) will be acquired. 

fused

quartz

focused

transducer

stand

Figure 3.1 Reference Experiment

Yr,w

defect

cube

block

focused

transducer

stand

Figure 3.2 Defect Experiment

Yr,s

Yd,s

Yd,w

It should be pointed out that all hardware connections (such as the co-axial cables and 

transducer search tube) and settings (such as damping, pulse rate, energy level on 

pulser/receiver unit) must be kept the same for both the reference and defect experiments. 

The only adjustable setting is the gain (or attenuation on Panametrics models) of the 

pulser/receiver unit. This is to ensure the accuracy of the system efficiency factor as stated 

above. 

B-3
In order to warrant the best possible data obtained in an optimal condition of a given scan 

system, extra care should also be taken on the specimen placement issues. Specimen 

placement involves the leveling of the specimen and orienting the specimen with respect to 

the scan system coordinates. These are the subjects of the following subsections. 

3.2 Specimen Leveling 

For a typical linear scan, the rule of thumb is to maintain a constant distance between the 

beam entry surface and the transducer face. This constant distance can in turn be related to 

the planar path that the scan bridges move about, assuming there is no bending of the scan 

bridges (see Section 4.2). This ensures the alignment of the specimen and the scan bridges to 

avoid the fluctuations of beam focusing and signal time-of-flight. This is referred as 

specimen leveling with constant water path, and the surface to be leveled is often the front 

surface of the specimen. A common technique of leveling a front surface is to perform a 

lengthy line scan on that surface. During the scanning, the amount of change in time-offlight of an echo from the front surface, as seen on the oscilloscope, determines the degree of 

tilting of the surface. One can then adjust, for instance, the screws of the sample stand to 

correct the tilt. However, given the relatively large size of the transducer (1′′ diameter for the 

5MHz transducer) and small dimension of the defect block (~1′′ cube), this technique does 

not work well in this case. The solution here is to level the surface of the sample stand 

instead. The leveling of the sample stand ensures the same for the front and back surfaces of 

the defect cube block, since they are parallel to each other as was required (Section 1). For 

the reference fused-quartz plate, the leveling is not as crucial because only single-shot Ascans are acquired. 

3.3 Specimen Orientation 

Based on past experience with the Sonix system, issues related to specimen orientation have 

frequently been the source of error and confusion. Often the C-scan images were rotationally 

disoriented or mirror-inverted from the actual specimen layout. The problem arises largely 

from the inconsistency between the specimen orientation (in the water tank) and the Sonix 

scan plan. To avoid such difficulty, it is recommended that the Sonix scan plan be set up to 

match exactly with the actual specimen orientation. As an example, Figure 3.3a illustrates a 

hypothetical specimen orientation and the matching Sonix C-scan line paths (see Section 9.5 

for detailed scan/step direction settings under FlexSCAN-C’s Scan Setup menu). If the 

bottom-up image convention (with origin at lower-left corner) is followed, then the 

orientation of the C-scan image, as depicted in Figure 3.3b, should match correctly with that 

of the specimen. It is also recommended to keep a drawing of the specimen orientation with 

respect to the scan plan and a copy of the details of the scan plan settings for future reference. 

B-4
defect

scan lines

Step direction

defect

origin origin

Figure 3.3 specimen and scan orientations Figure 3.4 resulting C-scan image Figure 3.3.a specimen and scan orientations Figure 3.3b resulting C-scan image 

3.4 Transducer Normalization 

In addition to specimen leveling, the normalization of the transducer is also an important but 

often difficult task. By normalization we mean to orient the transducer with respect to the 

beam entry surface in such a way that the sound beam enters the specimen with minimum 

energy loss and achieves the optimal focusing. For spherically focused transducers, a 

popular ring wave method of normalization has proven reliable. The ring wave method takes 

advantage of the time-of-flight difference between the outer transducer ring wave and inner 

main beam. As depicted in Figure 3.4b, when the transducer is very close to a flat surface, 

the central main component of the beam takes a longer time to travel back and forth than the 

outer ring components do. This results in a separation of the time domain front surface echo 

into a small leading ring signal and a large trailing main signal as shown in Figure 3.4b. If 

the transducer is well fabricated, the ring signal will reach its maximum when the transducer 

is perpendicular to the surface such that all ring components travel using the same amount of 

time. This phenomenon thus provides a practical way to normalize a focused transducer of 

axial symmetry. The degree of time separation between the ring and main components 

depends on the size, focal length and frequency of the transducer. For the 5MHz, 1′′

diameter, spherically focused transducer with focal length 8′′ at about 0.5′′ above a flat 

surface, the time separation is substantial. For a higher frequency transducer with shorter 

focal length and smaller diameter, the separation becomes less clear. In this case, the 

inseparable main and ring signals should be viewed as a whole and maximized in the process 

of transducer normalization. 

focused transducer

ring 

waves ring 

waves

main 

beam

main 

beam ring 

waves

time

Figure 3.4a “ring-wave” Figure 3.5 “ring-wave” s setup Figure 3.4b corresponding A-scan etup Figure 3.6 corresponding A-scan

B-5
4. System Calibration 

In addition to an optimal experimental setup, a thorough system calibration process is the key 

to data accuracy and should be conducted BEFORE any data acquisition. In this procedure, 

there are three elements in the system calibration process: pulser/receiver, mechanical scan 

bridges, and oscilloscope. It is also strongly recommended to follow all calibration 

procedures described in FlexSCAN-C user’s guide.

4.1 Pulser/Receiver

Important electronic parts like the pulser/receiver are often overlooked in the calibration 

process. While the accuracy of other aspects of the pulser/receiver matters, the single most 

critical function of the pulser/receiver for this procedure is the gain (or attenuation) setting, 

the only adjustable electronic parameters in the system (recall Section 3.1). Extra care 

should be taken in operating this setting. For example, the receiver of Panametrics 5052 is 

rated maximum output voltage of +0.5 volt into 50 Ohms. Any signal that has peak-to-peak 

amplitude exceeding 1 volt is subjected to distortion and loss of data accuracy. Thus, it is 

vital to maintain a linear undistorted operation of the gain (attenuation) setting in the 

pulser/receiver unit and acquire measurements in this linear range. A simple test of the 

linearity is to measure the peak-to-peak amplitude of a stationary signal (within the 

maximum output limit) with a sequence of gain settings that lie in the expected range of 

operation. The amplitude change in measurement should be linearly proportional to that in 

the gain settings. Proper remedy needs to be made if significant deviation from the linearity 

is observed. 

Mechanical Scan Bridges 

Typical problems with mechanical scan parts are scan bridge bending due to aging and scan 

backlash effects. Severe scan bridge bending may cause data loss and/or incorrect data 

registration. For example, heavy weight over time can cause the center of a scan bridge to 

buckle downward, which leads to a shorter water path in the central portion of scan. For a 

fixed narrow time gate in which UT data are digitized, a portion of the target UT signal may 

then shift out in this central scan path depending on the amount of bending. The 

misalignment problem may also arise when the beam entry surface of specimen has variable 

curvature. Because of these shortcomings, at most times it is good idea to turn ON the front 

surface follower feature in Gate Control window of FlexSCAN-C. 

The backlash effect frequently originates from excessive looseness in the lead screws of the 

mechanical scan bridge. This looseness can cause misalignment problem in data when 

scanned in bi-directional mode (i.e. taking data in both scan and return pass of a scan line). 

One way to determine the amount of backlash is to scan an object of well-defined shape and 

examine the degree of distortion in the C-scan image, especially the outlines of the object 

image. In FlexSCAN-C, the backlash effect may be compensated by software operation 

(Scan -> Backlash Correction). In any event, it is recommended to scan only in 

unidirectional mode (scan -> Scan Setup -> Bidirectional OFF) to reduce this effect.

B-6
Oscilloscope 

The Sonix digital oscilloscope comes with default settings, as seen in the A/D Offset of A/D 

8100 window, for the vertical baseline position of signal trace. Normally, these default 

settings are sufficient to keep the trace baseline in the middle (zero) of the scope display. In 

situations that the signal baseline deviates substantially from this zero position, the A/D 

Offset setting must be adjusted accordingly. 

Another problem with the Sonix digital scope is a constant time trace offset as seen in some 

systems using an external pulser/receiver unit. This is possibly due to inconsistent timing 

between the trigger signal and the initial transmitted pulse in the combination of 

pulser/receiver and Sonix A/D card. This offset, typically causing 1-2 s longer in a timeof-flight reading, should be pre-determined and compensated as much as possible. One way 

to determine this time trace offset is to take a time-of-flight measurement from a specimen of 

known thickness, e.g. the 1′′ fused-quartz reference plate. This can be done as follows: 

First proceed with the procedures of leveling the sample stand, transducer normalization with 

respect to sample stand, and determining the water wave speed as described in Sections 3.2, 

3.4 and 9.2. Next, place the fused-quartz plate on the sample stand, manually lower the 

transducer to be in contact with the front surface of fused-quartz plate, and then carefully 

remove the fused-quartz plate from below. In this way, an exact 1′′ water path is readily set 

for a time-of-flight measurement of the front surface echo from the sample stand surface. 

Follow Section 9.4 to calculate the time-of-flight and compare that with the Sonix scope 

reading. The difference is the offset needed to be compensated in all future time-of-flight 

measurements. Note that this time trace offset depends on system loading (the combination 

of pulser/receiver, transducer, cables, etc.) and must be re-calibrated if any system 

component and/or major setting changes. 

5. Data Format

Three types of UT data are acquired in this procedure: A-scan, multiple b-scan, and C-scans. 

By default, FlexSCAN-C generates a UT scan data file using the traditional DOS naming 

system: XXXXXXXX.YYY where X’s are the user supplied file name (8 characters 

maximum) and Y’s are the three-character file extension assigned by FlexSCAN-C. 

Files with CS1 extension are binary C-scans stored either in Sonix proprietary format or 

TIFF format. The former format can be read by any image processing software supporting 

RAW format. The actual data follow the first 9276-bytes header. Note that the image origin 

is at the lower left corner stored in row major. The TIFF format is one of the popular publicdomain file formats and should be supported by most image processing software. From the 

programming point of view, the Sonix proprietary format is the preferred format because it is 

easier to work with. 

Files with RF extension are multiple-line b-scans stored in a Sonix proprietary format, which 

is a special version of multi-page TIFF format. Files of this type can be accessed by 

FlexSCAN-C directly. Some image processing software also support this format. 

B-7
Files with TXT extension are numeral screen dump of A-scan traces and can be opened by 

any text file editor. It contains a short header followed by waveform data points in 256-level 

integer, separated by commas. It is always a good practice to maintain a concise file naming 

convention and provide such convention along with the corresponding data structure in a 

readme file for future reference and use. 

6. Reference Waveform Acquisition 

To ensure best data quality and minimal errors, it is advised to follow the steps below when 

acquiring the reference waveform. The transducer should have been mounted on the angular 

manipulator, which is in turn attached to the search tube of the scan bridge. 

The following steps need only to be done once for each new fused-quartz plate: 

• Measure and record the dimensions and weight of the fused-quartz plate. Deduce the 

density accordingly and check with the tabulated generic value (Section 9.3) if 

applicable. Take necessary action if the difference is significant. 

• Measure and record the UT speeds of the fused-quartz plate and check with the 

tabulated generic values (Section 9.3) if applicable. Take necessary action if the 

difference is significant. 

The following steps need to be done for each transducer loaded with the system at the 

beginning of the scans: 

• Determine the time trace offset (Section 4.3). 

• Measure and record the UT speed in water (Section 9.2). 

• Measure and record water temperature within 1-degree precision. 

Steps below are to be done for both low-frequency (5 MHz) and high-frequency transducers 

with matching fused-quartz plate: 

• Measure and record the UT speed in water (Section 9.2) when water 

quality/temperature changes significantly during the scans. Be sure to update the 

new water speed in FlexSCAN-C (under Edit->Configuration->couplant velocity). 

• Measure and record water temperature within 1-degree precision when temperature 

changes significantly during the scans. 

• Normalize transducer with respect to front surface using ring wave method (Section 

3.4). 

• Calculate the time-of-flight prediction of the front surface echo so that the 

geometric focus is set on the back surface (Section 9.2). Use the pre-determined 

plate thickness in the calculation. 

• Manipulate FlexSCAN-C’s digital scope to locate the front surface echo. Adjust 

water path until front surface echo appears at the predicted time instance as 

calculated in the last step. Be sure to account for the time trace offset if any 

(Sections 3.1 and 4.3, and Figure 3.1). 

• Manipulate FlexSCAN-C’s digital scope to display the back surface echo. 

• Measure the time-of-flight of the back surface echo. Check measurements against 

the predictions. Make correction if necessary. 

B-8
• Adjust both pulser/receiver’s gain setting (or attenuation setting on Panametrics 

505x series) and the A/D Gain setting in FlexSCAN-C’s A/D 8100 window so that 

the peak back surface waveform is about at 80% full screen height. Also set the 

time scale of FlexSCAN-C’s digital scope so that time resolution is sufficient (at 

least 20 time trace data points across the signal duration). 

• Check and adjust the baseline offset (A/D offset in A/D 8100 window) if necessary 

(Section 4.3). 

• Record all Sonix system settings. This can be done by properly arranging all 

FlexSCAN-C’s setting windows on the screen and then print screen from File 

menu. 

• Record all other experimental settings. 

• Take single-shot A-scan waveform of back surface echo. The time average feature 

should be turned ON to reduce noise. Use highest average number available. Ascan waveform data is obtained by entering File -> Export ... -> Scope to ASCII. 

Record peak-to-peak amplitude of the waveform. 

6. Defect Data Acquisition 

To ensure best data quality and minimal errors, it is advised to follow the steps below when 

acquiring the defect data. The defect depth in each side of the defect cube block should have 

been determined previously. The transducer should have been mounted on the angular 

manipulator, which is in turn attached to the search tube of the scan bridge. 

The following steps need only to be done once for each new defect cube block: 

• Measure and record the UT speeds of the defect cube block and check with the 

tabulated generic values (Section 9.3) if applicable. Take necessary action if the 

difference is significant. 

• Measure and record the dimensions and weight of the defect cube block. Deduce the 

density accordingly and check with the tabulated generic value (Section 9.3) if 

applicable. Take necessary action if the difference is significant. 

The following steps need to be done for each transducer loaded with the system at the 

beginning of the scans. This step can be skipped if it has been done in reference data 

acquisition. 

• Measure and record the UT speed in water (Section 9.2). 

• Measure and record water temperature within 1-degree precision. 

• Determine the time trace offset (Section 4.3). 

• Go to Edit -> Configuration -> Image Format to set C-scan format to Sonix 

proprietary format. 

The steps below are to be done for both low-frequency (5 MHz) and high-frequency 

transducers. For each transducer, repeat the applicable steps on every accessible side of the 

cube block: 

• Measure and record the UT speed in water (Section 9.2) when water 

quality/temperature changes significantly during the scans. Be sure to update the 

new water speed in FlexSCAN-C (under Edit->Configuration->couplant velocity). 

B-9
• Measure and record water temperature within 1-degree precision when temperature 

changes significantly during the scans. 

• Level the sample stand and set the defect cube block on the stand (Section 3.2). 

• Maintain a consistent and precise orientation of the defect cube block with respect 

to the scan system coordinates (Section 3.3). 

• Normalize transducer with respect to front surface of the defect cube block using 

ring wave method (Section 3.4). 

• Calculate the time-of-flight prediction of the front surface echo so that the true 

focus is set on the nearest defect surface (Section 9.4). Calculate the prediction for 

the time-of-flight of defect signal from the pre-determined defect depth. Also 

calculate the prediction for the time-of-flight of back surface echo from the predetermined cube dimensions. 

• Manipulate FlexSCAN-C’s digital scope to locate the front surface echo. Adjust 

water path until front surface echo appears at the predicted time instance. Be sure 

to account for the time trace offset if any (Section 4.3). 

• Manipulate FlexSCAN-C’s digital scope to locate the defect signal and back surface 

echo. 

• Measure the time-of-flight of the defect signal and back surface echo. Check 

measurements against the predictions. Make correction if necessary. 

• Adjust both pulser/receiver’s gain (or attenuation on Panametrics 5052x series) 

setting and the A/D Gain setting in FlexSCAN-C’s A/D 8100 window so that the 

maximum defect waveform is about at 80% full screen height (Section 9.5). 

• Check and adjust the baseline offset (A/D offset in A/D 8100 window) if necessary 

(Section 4.3). 

• Set proper time gate location and width for defect signal in FlexSCAN-C’s Gate 

Control window. Make sure the sampling rate is at least 100 MHz (Section 9.5). 

Also turn on Front Follow gate (Sections 4.2 and 9.5). 

• Record all Sonix system settings. This can be done by properly arranging all 

FlexSCAN-C’s setting windows on the screen and then print screen from File 

menu. 

• Record the cube block orientation drawing and all other experimental settings. 

• Take single-shot A-scan waveform of defect at peak position with time average 

feature ON. This is done by entering File -> Export ... -> Scope to ASCII. Record 

peak-to-peak amplitude of the defect waveform. 

• Turn OFF time average feature (time averaging requires time-consuming multiple 

data acquisitions at the same scan which is not possible in high-speed scans such as 

c- or b-scans. The scan speed will be greatly compromised if this feature is not 

turned off). 

• Go to Scan -> Scan Setup. Set all necessary parameters for C-scan. Make sure the 

scan and step increments are 5 mils for 5 MHz scan, and 2 mils for high-frequency 

scans, respectively (see example in Section 9.5). 

• Go to Scan -> Scan Go to dry run C-scan data acquisition. 

• Make changes such as scan sizes (pixels) in Scan Setup if necessary. 

• Repeat last three steps until data quality criterion is met. 

• Follow the last four steps to acquire b-scan data (see example in Section 9.5). 

B-10
7. Key Parameter Calculations/Settings 

In this section, the methods of calculation for all key parameters used in this procedure are 

given. In support of these calculations and clarification of the procedure contents, some key 

terms are first described. Examples of Sonix scan settings are also attached for future 

reference. 

7.1 Key Terminology 

Time-of-flight (TOF) in UT NDE is the round-trip time that ultrasound travels in a medium 

(or media) between transducer face and a point of interest, or between two points of interest. 

The horizontal time axis as seen on oscilloscope measures the time-of-flight of signals. 

Water path is the distance between the transducer face and the front surface of the specimen 

in an immersion test. 

Geometric and true focal lengths and equivalent diameter are the most important 

transducer parameters for a spherically focused transducer. Geometric focal length is the 

axial length (measured from the transducer face) as determined by geometric optics with 

respect to a given lens curvature. True focal length is the one most transducer specifications 

refer to, indicating the actual focal depth. Usually true focal length is shorter than geometric 

focal length. Equivalent diameter is the transducer size (diameter) produced by transducer 

characterization procedure, not necessarily the same as the manufacturer’s specification. 

Multiple-line B-scan takes an A-scan (waveform) at each scan position in a two-dimensional 

C-scan path. The results are three-dimensional A-scan data covering the volume being 

scanned. 

7.2 UT speed in water 

A simple measurement of the longitudinal-wave speed in water can be done by using two 

reference signals from a flat surface. In most cases, the front surface echoes are conveniently 

used as the reference signals. First normalize the transducer with respect to the flat surface 

(Section 3.4). Measure the TOF, T1, of a reference point on the front surface echo, say, at the 

peak position. Secondly, move the transducer up or down a known distance, D, 

perpendicular to the flat surface. In a Sonix immersion system, this can be easily done by 

moving the motorized vertical scan bridge on which the transducer search tube attaches. The 

distance moved can be monitored in the Motor window in FlexSCAN-C. Next, measure the 

TOF, T2, of the same peak reference point on the front surface echo at the new position. 

Finally, by simple physics of motion, 

TT 12

2D speed water − =

B-11
where | | means the absolute difference. For example, let D=2 inch=5.08cm, T1=30 μs 

(microsecond; 1 μs =10-6 second) and T2=98.65 μs then water speed = 0.148 cm/μs (0.0583 

in/μs) which is typical for tap water at 70°F. This water speed should also match with the 

couplant velocity in FlexSCAN-C (accessed from Edit menu -> Configuration -> Couplant 

Velocity). 

7.3 UT speeds in defect cube block/fused-quartz plate 

Longitudinal-wave speed in cube block/fused-quartz plate can be measured similar to that in 

water. The difference is that the back surface echo taken from the defect cube block or 

fused-quartz plate (without moving the transducer up or down) replaces the second front 

surface echo in the case of water. For example, let the TOF of front surface be 20μs and 

TOF of back surface echo be 28.2 μs. From the above formula, the longitudinal-wave speed 

in a 1′′ Ti-6Al-4V cube block is 0.62 cm/μs. Shear-wave speed, however, requires the use of 

a shear-wave transducer measured in contact mode. One can take the first and the second 

bounces of the back surface echoes as the reference signals. If no shear-wave transducer is 

available, the values in Table 9.1 may be used. 

Table 9.1 UT and material properties of several frequently used materials in ETC 

Material Longitudinalwave speed 

(cm/μs) 

Shear-wave 

speed (cm/μs) 

Density 

(g/cm3) 

Water 0.148 NA 1.00 

Ti-64 0.620 0.319 4.43 

IN718 0.610 0.326 7.86 

Fused-quartz 0.597 0.309 2.20 

7.4 Water path 

Given transducer focal lengths, wave-speeds in water and in the specimen, the correct water 

path and the corresponding TOF can be easily computed. Let the geometric and true focal 

lengths be Fg and Ft, respectively. Also denote longitudinal wave-speeds in water, fusedquartz and defect cube block as Vw, Vf, and Vs For the reference experiment, the following 

formula applies: 

sr, w

f

wr,g Y V

V YF +=

For the defect experiment, the parameters change slightly in the same formula: 

sd, w

s wd,t Y V

V YF +=

B-12
where the subscripted Y’s are the water paths and specimen thickness/depths described in 

Section 3.1 and Figures 3.1 and 3.2. The corresponding TOFr for the back surface echo 

(measured from beginning of the time trace) is the sum of TOF for front surface echo (also 

from beginning) and TOF for the back surface echo (measured after the front surface echo) in 

the reference experiment: 

s

sr,

w

wr,

r wr, sr, V

2Y

V

2Y

 TOF TOF TOF +=+=

Likewise, TOFd for the defect in the defect experiment is 

d,w d,s

d d,w d,s

w s

2Y 2Y

TOF TOF TOF . V V = + =+

7.5 Examples of Sonix FlexSCAN-C scan settings 

Figures 9.1 through 9.5 are the actual scan settings used in the first Ni real defect. Most 

settings should be suitable for future use except those specifics on transducer characteristics 

and defect size. Figures 9.1 and 9.2 are examples of the SCAN SETUP menu in Sonix 

FlexSCAN-C settings for low-frequency (5 MHz) and high-frequency C-scans, respectively. 

Figure 9.3 shows the SCAN SETUP menu for high frequency b-scan. Figures 9.4 and 9.5 are 

examples of screen snap shot of Sonix FlexSCAN-C showing the various settings for lowfrequency (5 MHz) and high-frequency scans. 

8. Further Contact 

Questions/corrections/comments are welcome and should be forwarded to 

C. Thomas Chiou (515)294-0299 cchiou@cnde.iastate.edu

Mike Keller (513)552-4643 mike_keller@geae.com

Jeff Umbach (561)796-6047 umbachj@pwfl.com 

Andrei Degtyar (860)565-3987 degtyaa@pweh.com 

B-13
B-14

Figure 9.1 The SCAN SETUP menu in Sonix FlexSCAN-C for low-frequency (5 MHz) C-scan settings 
B-15

Figure 9.2 The SCAN SETUP menu in Sonix FlexSCAN-C for high frequency C-scan settings 
B-16

Figure 9.3 The SCAN SETUP menu in Sonix FlexSCAN-C for high frequency b-scan settings 
B-17

Figure 9.4 A screen snap shot of Sonix FlexSCAN-C shows the various settings for low-frequency (5 MHz) scan 
B-18

Figure 9.5 A screen snap shot of Sonix FlexSCAN-C shows the various settings for high-frequency scan
REFERENCE, 

 

1. Gray, T.A., “Application of Measurement Models to Specification of Ultrasonic 

Inspections,” in Review of Progress in QNDE, Vol. 16B, D.O. Thompson and D.E. 

Chimenti, eds., Plenum, New York, 1997, pp. 2061-2068. 

B-19/B-20
APPENDIX C—NICKEL SMALL-DIAMETER BILLET DATA

The following are the results from the phased array inspection of the 5′′ diameter Waspaloy billet 

reference standard. 

Waspaloy, f = 5 MHz, Depth = 2.63′′, ER-focus = 2.63′′, WP = 4′′, BW = 100 mils, Gain = 15 dB 

Waspaloy, f = 5 MHz, Depth = 2.25′′, ER-focus = 2.25′′, WP = 4′′, BW = 100 mils, Gain = 10 dB 

C-1
Waspaloy, f = 5 MHz, Depth = 2.25′′, ER-focus = 2.25′′, WP = 4′′, BW = 100 mils, Gain = 10 dB 

Waspaloy, f = 5 MHz, Depth = 1.87′′, ER-focus = 1.87′′, WP = 4′′, BW 100 mils, Gain = 10 dB 

C-2
Waspaloy, f = 5 MHz, Depth = 1.13′′, ER-focus = 1.13′′, WP = 4′′, BW = 100 mils, Gain = 13 dB 

Waspaloy, f = 5 MHz, Depth = 0.75′′, ER-focus = 0.75′′, WP = 4′′, BW = 100 mils, Gain = 13 dB 

C-3
Waspaloy, f = 5 MHz, Depth = 0.48′′, ER-focus = 0.48′′, WP = 4′′, BW = 100 mils, Gain = 15 dB 

Waspaloy, f = 5 MHz, Depth = 0.2′′, ER-focus = 0.2′′, WP = 5′′, BW = 100 mils, Gain = 20 dB 

C-4
APPENDIX D—TITANIUM SMALL-DIAMETER BILLET DATA

The following are the results from the phased array inspection of the 5′′ diameter Ti-6Al-4V 

billet reference standard. 

Titanium, f = 5 MHz, Depth = 3.0′′, ER-focus = 3.0′′, WP = 4′′, BW = 100 mils, Gain = 10 dB 

Titanium, f = 5 MHz, Depth = 2.63′′, ER-focus = 2.63′′, WP = 4′′, BW = 100 mils, Gain = 12 dB 

D-1
Titanium, f = 5 MHz, Depth = 2.25′′, ER-focus = 2.25′′, WP = 4′′, BW = 100 mils, Gain = 13 dB 

Titanium, f = 5 MHz, Depth = 1.87′′, ER-focus = 1.87′′, WP = 4′′, BW = 100 mils, Gain = 15 dB 

D-2
Titanium, f = 5 MHz, Depth = 1.13′′, ER-focus = 1.13′′, WP = 4′′, BW = 100 mils, Gain = 6 dB 

Titanium, f = 5 MHz, Depth = 0.75′′, ER-focus = 0.75′′, WP = 4′′, BW = 100 mils, Gain = 15 dB 

D-3
Titanium, f = 5 MHz, Depth = 0.48′′, ER-focus = 0.48′′, WP = 4′′, BW = 100 mils, Gain = 10 dB 

Titanium, f = 5 MHz, Depth = 0.2′′, ER-focus = 0.275′′, WP = 4′′, BW = 100 mils, Gain = 15 dB 

D-4