Cold Spray Process Development for the Reclamation of the 

Apache Helicopter Mast Support 

by P. F. Leyman and V. K. Champagne 

ARL-TR-4922 August 2009 

Approved for public release; distribution is unlimited. 
NOTICES 

Disclaimers 

The findings in this report are not to be construed as an official Department of the Army position unless 

so designated by other authorized documents. 

Citation of manufacturer’s or trade names does not constitute an official endorsement or approval of the 

use thereof. 

Destroy this report when it is no longer needed. Do not return it to the originator. 
Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5069 

ARL-TR-4922 August 2009 

Cold Spray Process Development for the Reclamation of the 

Apache Helicopter Mast Support 

P. F. Leyman 

Data Matrix Solutions, Inc. 

and 

V. K. Champagne 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution is unlimited.
ii

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering 

and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, 

including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson 

Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to 

comply with a collection of information if it does not display a currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

August 2009 

2. REPORT TYPE 

Final 

3. DATES COVERED (From - To) 

May 2007–December 2008 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Cold Spray Process Development for the Reclamation of the Apache Helicopter 

Mast Support 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

5e. TASK NUMBER 

6. AUTHOR(S) 

P. F. Leyman and V. K. Champagne 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

U.S. Army Research Laboratory 

ATTN: RDRL-WMM-C 

Aberdeen Proving Ground, MD 21005-5069 

8. PERFORMING ORGANIZATION 

 REPORT NUMBER 

ARL-TR-4922 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 

11. SPONSOR/MONITOR'S REPORT 

 NUMBER(S) 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

Approved for public release; distribution is unlimited. 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

The U.S. Army Research Laboratory at Aberdeen Proving Ground, MD, has developed a novel process for repairing and 

rebuilding damaged aluminum components using Supersonic Particle Deposition, commonly referred to as cold spray. A 

Centerline Model No. SSM-P3300 Portable Cold Spray Deposition System was used to deposit a highly adherent, dense 

aluminum composite material to repair corrosion damage pits and rebuild the snap ring groove and gear teeth on the mast 

support on an Army helicopter. ARL performed microstructural analysis as well as adhesion, fatigue, and corrosion tests to 

evaluate the characteristics of the cold spray aluminum composite coatings. The cold spray deposited material was 

subsequently machined using conventional machining tools to dimensionally restore the component to its original condition. 

Final testing and approval for implementation of this repair procedure is in progress. 

15. SUBJECT TERMS

cold spray, helicopter repair 

16. SECURITY CLASSIFICATION OF: 

19a. NAME OF RESPONSIBLE PERSON

V. K. Champagne 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified

c. THIS PAGE 

Unclassified

17. LIMITATION 

 OF 

 ABSTRACT 

UU 

18. NUMBER 

 OF 

 PAGES 

32 19b. TELEPHONE NUMBER (Include area code) 

(410) 443-0745 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 
iii

Contents 

List of Figures iv

List of Tables v

Acknowledgments vi

1. Objective 1

2. Introduction 1

3. Components Needing Repair 2

3.1 Corrosion Damage Pits....................................................................................................3 

3.2 Mechanical Damage Repair of Snap Ring Groove .........................................................5 

3.3 Damage Repair of the Splines.........................................................................................6 

4. Cold Spray Deposition Trials Conducted at ARL 7

4.1 Cold Spray Deposition System .......................................................................................8 

4.2 Powders ...........................................................................................................................8 

4.3 Microstructural Analysis ...............................................................................................10 

4.4 Hardness Measurements................................................................................................12 

4.5 Bond Strength................................................................................................................13 

4.6 Fatigue Testing..............................................................................................................13 

4.7 Corrosion Test Results ..................................................................................................14 

4.8 Cold Spray Demonstration ............................................................................................14 

5. Demonstration Conducted at Fort Hood, TX 17

6. Discussion 20

7. Conclusions 21

List of Symbols, Abbreviations, and Acronyms 22

Distribution List 23 
iv

List of Figures 

Figure 1. Aluminum helicopter mast support. ................................................................................2 

Figure 2. Corrosion pits in the lower lip of the snap ring groove...................................................3 

Figure 3. Cross section of the pitted surface...................................................................................3 

Figure 4. Blending out of the corrosion pits with a grinding tool...................................................4 

Figure 5. Area filled with cold spray material. ...............................................................................4 

Figure 6. Surface ground or machined back to original surface.....................................................4 

Figure 7. Mechanical damage to the snap ring groove of the Army mast support.........................5 

Figure 8. Complete removal of the snap ring groove. ....................................................................5 

Figure 9. Area filled with cold spray material. ...............................................................................6 

Figure 10. Cold spray material machined back to the original dimensions....................................6 

Figure 11. Mechanical damage to the splines on the Army helicopter mast support. ....................7 

Figure 12. Operator using a Centerline Portable Cold Spray System to repair a rotorcraft 

component..................................................................................................................................8 

Figure 13. A schematic of the Centerline Portable Cold Spray System. ........................................8 

Figure 14. SEM photomicrograph of CP aluminum powder (Valimet H-12). ...............................9 

Figure 15. SEM photomicrograph of A050-aluminum/aluminum oxide powder. .......................10 

Figure 16. SEM micrograph of A027-aluminum/zinc/aluminum oxide powder..........................10 

Figure 17. Microstructural analysis of CP-aluminum cold spray coating. ...................................11 

Figure 18. Microstructural analysis of aluminum/aluminum oxide cold spray coating. ..............12 

Figure 19. Microstructural analysis of the aluminum/zinc/aluminum oxide cold spray 

coating......................................................................................................................................12 

Figure 20. Plot of RCB fatigue test results for cold spray aluminum on 7075 aluminum RCB 

fatigue specimens. (Australian Defence Science and Technology Organization)..................14 

Figure 21. Mast support test section as received. .........................................................................15 

Figure 22. Test section after cleaning and grinding out the pits...................................................15 

Figure 23. High magnification of cold spray repair to corrosion damage conducted at ARL......16 

Figure 24. Cold spray repair on mechanical damage to a snap ring groove conducted at ARL...16 

Figure 25. Corrosion pits in lower lip of snap ring groove before cold spray..............................17 

Figure 26. Corrosion pits after cold spray fill and restoring back to original dimensions. ..........17 

Figure 27. Close up of a corrosion pit filled with cold spray aluminum, machined back to the 

original dimensions..................................................................................................................18 

Figure 28. Mechanical damage on a snap ring groove. ................................................................18 
v

Figure 29. Areas on a snap ring groove and spline requiring repair.............................................19 

Figure 30. Cold spray aluminum fill machined back to the original dimensions.........................19 

Figure 31. Machinist performing re-contouring of the cold spray aluminum repair to the 

original dimensions..................................................................................................................19 

List of Tables 

Table 1. Powder composition (volume %). ....................................................................................9 

Table 2. Hardness and bond strength............................................................................................13 

Table 3. Process parameters..........................................................................................................15 
vi

Acknowledgments 

We wish to thank Joshua Morales and Raymond Boland of Fort Hood, TX, for coordinating the 

cold spray demonstration at Ft. Hood and for the acquisition of actual helicopter parts to validate 

the repair process. Appreciation is also extended to Steve Howell and Courtney Guasti of the 

Aviation and Missile Research, Development and Engineering Center (AMRDEC) as well as 

Michael Kane and George Liu of the Aviation and Missile Command (AMCOM) for their 

continued support of cold spray technology. 
1

1. Objective 

The principal objective of this applied research effort was to demonstrate the ability of the cold 

spray process to repair damaged aluminum mast supports with the use of a commercial, field 

portable, cold spray system capable of restoring the dimensions of corroded or badly worn 

components, resulting in a repair that would be considered flight worthy. 

2. Introduction 

Corrosion and mechanical damage has rendered a number of 7075-T73 aluminum mast supports 

non-serviceable for continued use on Army helicopters. The U.S. Army Research Laboratory 

(ARL) Center for Cold Spray at Aberdeen Proving Ground, MD, developed a Supersonic 

Particle Deposition (SPD) process, more commonly called cold spray, to reclaim aluminum and 

magnesium components that shows significant improvement over existing methods and is in the 

process of qualification for use on rotorcraft.1 The cold spray repair has shown superior 

performance in the tests conducted to date, is inexpensive, can be incorporated into production, 

and has been modified for field repair, making it a feasible alternative over competing 

technologies. The goal of this effort was to repair both the corrosion and mechanical damage by 

blending and machining damaged areas, rebuilding lost material using cold spray with 

aluminum-based powder, and final blending and machining to the original dimensions. 

Protective finishes, such as a conversion coating, primer, and topcoat, may be applied to the 

repaired areas of the cold spray coating. While it is possible to perform a remediation without 

rebuilding lost material, the number of times this type of repair could be performed would be 

limited. By using cold spray to rebuild lost material, the component could be remediated as 

many times as necessary until its safe-life has been reached. The predominant risks associated 

with this repair would be foreign object damage should cold spray material de-bond to 

generate debris. 

 1

Champagne, V. K. The Repair of Magnesium Rotorcraft Components. 61st Meeting of the Society for Machinery Failure 

Prevention Technology, Cold Spray, April 2007. 
2

3. Components Needing Repair 

The purpose of this program is to demonstrate and validate the cold spray deposition of 

aluminum-based material using a Centerline Model SSG-3800 GDS Cold Spray System as a cost 

effective, environmentally acceptable technology to repair corrosion damage pits and rebuild the 

snap ring groove and gear teeth on the mast supports used on Army helicopters. 

Currently, there are 50 helicopter mast supports that are unserviceable with no viable means to 

repair the component for service. ARL was requested to perform spray trials on a test section of 

an Army mast support and then provide technical support to the Aviation and Missile Research, 

Development and Engineering Center (AMRDEC) to perform the cold spray demonstration on 

an actual component at Dyn-Corp in Killeen, TX, to assess the feasibility of restoring an 

unserviceable component to service. This repair effort focused on three types of damage—

corrosion pits along the lower lip of the snap ring groove, mechanical damage on the upper lip of 

the snap ring groove, and mechanical damage to the gear tooth. A helicopter mast support is 

shown in figure 1. 

Figure 1. Aluminum helicopter mast support. 
3

3.1 Corrosion Damage Pits 

The first type of repair was performed on typical corrosion pitting damage shown near the lower 

lip of the snap ring groove on the Army helicopter mast support, as seen in figure 2. The pits, 

shown as a cross section in figure 3, were blended out as shown in figure 4, thereby reducing 

stress concentrators, and an aluminum coating was applied via cold spray to rebuild to original 

dimensions, as schematically shown in figure 5. A final machining and blending restored the 

original surface, as shown in figure 6. 

Figure 2. Corrosion pits in the lower lip of the snap ring groove. 

Figure 3. Cross section of the pitted surface. 
4

Figure 4. Blending out of the corrosion pits with a grinding tool. 

Figure 5. Area filled with cold spray material. 

Figure 6. Surface ground or machined back to original surface. 

The strategy for repairing the corrosion pits was to blend out the pit using either a grinding tool 

or machining to provide a clean surface. The surface was then grit blasted with 60-grit 

aluminum oxide to promote adhesion of the cold spray filler to the substrate surface. The top 
5

surface of the cold spray filler was then surface ground or machined back to the original surface 

as schematically illustrated in figures 3–6. 

3.2 Mechanical Damage Repair of Snap Ring Groove 

Figure 7 shows the second type of repair that would be performed on the mechanical damage. 

To demonstrate this repair, the entire snap ring groove area would be removed, as shown in 

figure 8. The damaged region cross section is completely removed (figure 8), the cold spray 

material is deposited on the entire area (figure 9), and then it is contoured by re-machining to the 

original shape and dimension (schematically depicted in figure 10). 

Figure 7. Mechanical damage to the snap ring groove of 

the Army mast support. 

material. 

Area to be removed 

and filled with Cold 

Spray 

Figure 8. Complete removal of the snap ring groove. 
6

Area filled with Cold 

Spray 

Figure 9. Area filled with cold spray material. 

Figure 10. Cold spray material machined back to the 

original dimensions. 

3.3 Damage Repair of the Splines 

An additional area where mechanical damage occurs is on the splines, as shown in figure 11. To 

demonstrate the effectiveness of the cold spray repair method, a section of the spline was 

mechanically removed using a milling machine, filled in using cold spray, then contoured via remachining to the original dimensions. 
7

Figure 11. Mechanical damage to the splines on the Army 

helicopter mast support. 

4. Cold Spray Deposition Trials Conducted at ARL 

The first phase of this effort was a laboratory demonstration conducted at ARL. ARL developed 

a material and cold spray process specification to deposit an aluminum-based material and 

demonstrated this capability on a test section of mast support. The mast support is fabricated 

from aluminum alloy 7075-T73; therefore, a cold spray coating of aluminum-based material 

would be compatible with regards to corrosion. Adequate adhesion is also necessary so that cold 

spray material does not de-bond and the ensuing foreign object damage can be avoided. The 

Centerline Model SSM-P3300 Portable Cold Spray System (figure 12) was used to deposit the 

cold spray aluminum coating on the test section of the Army helicopter mast support supplied to 

ARL. A schematic of the Centerline Cold Spray System is shown in figure 13. 
8

4.1 Cold Spray Deposition System 

Figure 12. Operator using a Centerline Portable Cold Spray System to repair a rotorcraft component.

Figure 13. A schematic of the Centerline Portable Cold Spray System. 

4.2 Powders 

Three potential cold spray aluminum-based coating candidates were identified that can be used 

for repairing and rebuilding damaged aluminum components using the low pressure deposition 

process. The coatings were deposited using a feedstock powder composed of commercially pure 

aluminum (CP-Al), an aluminum/aluminum oxide mixture (A050), or an 
9

aluminum/zinc/aluminum oxide mixture (A027). The volume % composition of each feedstock 

powder is listed in table 1. The CP-Al powder is available from Valimet, Inc., while the A027 

and A050 mixtures are available from Centerline (Windsor) Limited. 

Table 1. Powder composition (volume %). 

Powder Aluminum Zinc Aluminum Oxide 

CP aluminum 100 — — 

A050 70 — 30 

A027 65 15 25 

Scanning electron microscope (SEM) examination of the three feedstock powders was performed 

to analyze the structure and composition of each of the powders. The CP-Al powder has a 

spherical morphology with a particle size distribution range of 7–28 μm with an average particle 

size of 10.6 μm (figure 14). Since pure aluminum powder is softer than aluminum alloys such as 

7075, two additional powder mixtures that contained aluminum oxide were evaluated. The 

aluminum oxide particles increase the hardness of the resultant coating and impart 

increased wear resistance. A050 powder contained 5–25 μm aluminum powder and 100–200 μm 

angular shaped aluminum oxide particles (figure 15). A027 powder is a mixture of the same 

aluminum powder and aluminum oxide particles as A050 but with the addition of 1–10 μm 

zinc powder (figure 16). 

Figure 14. SEM photomicrograph of CP aluminum powder (Valimet H-12). 
10

Figure 15. SEM photomicrograph of A050-aluminum/aluminum oxide powder. 

Figure 16. SEM micrograph of A027-aluminum/zinc/aluminum oxide powder. 

4.3 Microstructural Analysis 

Coatings deposited using all three powders were cross-sectioned and metallographically 

prepared. A representative scanning electron micrograph for each coating is shown in figures 17, 

18, and 19. The coatings exhibit a fully dense structure with no visible voids and good bonding 

Alumina Particle 

Aluminum 

Zinc 

Alumina Particle 

Aluminum 
11

between the coating and the substrate. The bonding mechanism of cold spray is analogous to 

that of explosive cladding; whereas, the formation of a solid-state jet of metal occurs at the 

impact point between the particle and the substrate. The coating material is in intimate contact 

with the substrate forming a metallurgical bond as a result of the severe plastic deformation of 

the accelerated particle impact and is referred to as Super Plastic Agglomerate Mixing (SPAM).2

 

Figure 17. Microstructural analysis of CP-aluminum cold spray coating. 

 2

Champagne, V. K.; Helfritch, D.; Leyman, P. F.; Grendahl, S.; Klotz, B. Interface Material Mixing Formed by the 

Deposition of Copper on Aluminum by Means of the Cold Spray Process. J Thermal Spray Tech. 2005, 14 (3), 330–334. 
12

Figure 18. Microstructural analysis of aluminum/aluminum oxide cold spray coating.

Figure 19. Microstructural analysis of the aluminum/zinc/aluminum oxide cold spray coating. 

4.4 Hardness Measurements 

The hardness of the cold spray coatings deposited using cp-aluminum, A050 and A027 powders 

measured from metallographic cross sections with a Wilson Tukon 240B Micro-Hardness Tester 

using a Vickers indenter at a load of 500 g. Table 2 shows a comparison between the hardness of 

all three powders. The tremendous plastic deformation of each particle as it impacts the surface 

Alumina Particle 

Zinc 

Aluminum 

Cold Spray Al/Alumina 

Aluminum Substrate 

Alumina Particle 
13

of the substrate during the cold spray process results in microstructural changes that increase the 

hardness. It has been well established that cold spray is considered to be a powder shock 

compaction and consolidation process resulting in high localized strain and substantial grain 

refinement via fracturing or the formation of sub-grain structures.3 Therefore, an increase in 

hardness, commensurate with the amount of plastic deformation of each particle during 

consolidation, was anticipated. Even though this consolidation theory has been associated with 

the deposition of powder mixtures, it is apparent that as a result of the high localized strain that 

occurs within each particle during impact the conditions were satisfied for significant grain 

refinement. The aluminum oxide particles in the A027 and A050 powders not only act as a 

hammer to aid in compaction of the coating, their entrapment in the coating results in an 

increased hardness of the resultant coatings as compared to the pure aluminum coating (table 2). 

The coating produced using the A027 powder yielded the hardest coating. 

Table 2. Hardness and bond strength. 

Powder 

Hardness 

(Vickers) 

Bond Strength 

(psi) 

CP aluminum 46.2 3300 

A050 60.1 8184 

A027 66.9 4948 

4.5 Bond Strength 

Adhesion bond bar tensile tests, as per the American Society for Testing and Materials (ASTM) 

C633-014, were performed on 0.020-in thick coatings deposited on the 1-in diameter surface of 

the 2.5-in-long 6061-T6 aluminum alloy bond bars. FM 1000 adhesive film manufactured by 

Cytec Engineered Materials was used to glue the top surface of the coating to another 

1 in × 2.5 in bond bar and cured for 3 h at 160 °C. The adhesively bonded bars were then 

threaded into the cross-heads of a tensile test machine and pulled apart. The loads were 

measured and converted to tensile strength. The results of the three different coatings are listed 

in table 2. Even though all three coatings failed cohesively within the coating, the coatings 

containing the aluminum oxide particles showed increased adhesion to the aluminum alloy 

substrate due to the hammer effect of the aluminum oxide as compared to the 

pure aluminum coating. 

4.6 Fatigue Testing 

Rotating cantilever beam (RCB) testing was performed on aluminum alloy 7075-T651 straight 

shank specimens, which had been grit blasted with 60-grit aluminum oxide particles at 30 psi 

pressure and then coated with a .010-in-thick coating of cold spray CP-aluminum. The RCB 

 3Stoltenhoff, T.; Kreye, H.; Krommer, W.; Richter, H. Cold Spraying-from Thermal Spraying to High Kinetic Energy 

Spraying. HVOF Colloquium 2000, Gemeinschaft Thermisches Spritzen e.V., 2000, 29–38. 

4

Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings, Annual Book or ASTM Standards, 

American Society for Testing and Materials, Vol. 3. 2001. 
14

fatigue tests are performed at fully reversed (r = –1) loading at loading frequency of 100 Hz 

(6000 rpm), similar to the RR Moore fatigue testing. These were compared to specimens that 

were uncoated in addition to specimens that had been grit blasted using the same process as the 

coated specimens. The plot of the resultant data is shown in figure 20. The uncoated and grit 

blasted specimens had very similar cycles before failure, while the cold spray aluminum coated 

specimens had a consistently higher number of cycles before the specimens failed. The cold 

spray aluminum coating had an improved fatigue life and enhanced the fatigue performance of 

the 7075 aluminum alloy. 

Figure 20. Plot of RCB fatigue test results for cold spray aluminum on 7075 aluminum RCB 

fatigue specimens. (Australian Defence Science and Technology Organization) 

4.7 Corrosion Test Results 

Corrosion testing was performed on aluminum alloy 7075-T651 panels that had been coated with 

0.015 in of cold spray CP-aluminum. The coated panels underwent neutral salt spray testing 

(NSS), as per ASTM B117-85.5

 After 7000 h in the salt spray chamber, there was no visible 

evidence of corrosion of the AA7075-T651 substrates. The tests were conducted at the 

Australian Defence Science and Technology Organization. 

4.8 Cold Spray Demonstration 

Cold spray trials were conducted on a test section of the Army helicopter mast support to 

demonstrate that the aluminum based coating could be used to fill in both the corrosion pits and 

the mechanical damage areas and be ground and/or machined back to the original specifications 

without delaminating from the substrate material. The A027 feedstock powder, which 

 5

Standard Test Method for Salt Spray (Fog) Testing; ASTM-B-117-85; Annu. Book ASTM Stand. 2001. 
15

had yielded good microstructure, hardness, and adhesion performance, was deposited on 

the test section of the mast support employing a circular nozzle at the process parameters 

listed in table 3. 

Table 3. Process parameters. 

Nozzle temperature 350 °C 

Gun air pressure 85–90 psi 

Standoff distance 5–10 mm 

Powder feed setting 20% 

The results of the initial demonstration for the corrosion damage are shown in figures 21–23. 

Figure 21. Mast support test section as received. 

Figure 22. Test section after cleaning and grinding 

out the pits. 
16

Figure 23. High magnification of cold spray repair to corrosion damage conducted at ARL. 

Cold spray trials were also performed on the snap ring groove by removing a section of the snap 

ring groove to about 0.50 in deep and 1.0 in long into the snap ring groove (figure 19) and then 

filling it with cold spray aluminum above the surface of the snap ring grove. The excess material 

was machined back to the original surface contour of the component, as seen in figure 24. 

Metal removed from 

ring groove 

Areas to be removed 

and filled with Cold 

Spray 

Area filled with 

Cold Spray 

Re-machined 

ring groove 

Figure 24. Cold spray repair on mechanical damage to a snap ring groove conducted at ARL. 
17

5. Demonstration Conducted at Fort Hood, TX 

After the successful completion of the first phase, the second phase of the demonstration was 

initiated, which consisted of remediation at Ft. Hood, TX, on otherwise non-serviceable, 

Category D hardware. All process feasible cold spray repairs similar to those developed at ARL 

on scrap components, but at other locations on actual hardware, were also evaluated. The 

Centerline Portable Cold Spray System was transported to the test site to perform a 

demonstration of the process on both corrosion pits (figures 25–27) and mechanical damage 

(figures 28–30) on a full-size scrap Army mast support component. The final machining was 

done by the machine shop on site, as shown in figure 31.

Figure 25. Corrosion pits in lower lip of snap ring groove before cold spray. 

Figure 26. Corrosion pits after cold spray fill and restoring back to original dimensions. 
18

Figure 27. Close up of a corrosion pit filled with cold spray aluminum, machined back 

to the original dimensions. 

Figure 28. Mechanical damage on a snap ring groove. 
19

Figure 29. Areas on a snap ring groove and spline requiring repair. 

Figure 30. Cold spray aluminum fill machined back 

to the original dimensions. 

Figure 31. Machinist performing re-contouring of the cold 

spray aluminum repair to the original dimensions. 
20

6. Discussion 

The microstructural analysis, adhesion, fatigue, and corrosion testing results obtained from this 

study indicated that there are three cold spray aluminum composite materials that are viable 

candidates for remediation repair of 7075-T6 aluminum components using the portable 

Centerline Cold Spray System. An aluminum composite material using the cold spray process 

was applied to all three types of repair during the on-site demonstration. The corrosion pits and 

the mechanical damage on the three targeted sections of the Army helicopter mast support were 

successfully repaired. The machinability and structural integrity of the cold spray material was 

determined to be acceptable and the method was demonstrated to be capable of repairing both 

corrosion pits and mechanical damage on both the snap ring groove and the splines. 

Therefore, cold spray has proven to be a viable and cost-effective repair process for the 

remediation of an otherwise unserviceable component critical to the operation of the Army 

helicopter.6 Final testing and approval to implement this repair procedure is currently in 

progress. Further process development using alternative powder formulations, including cp-Al 

are being evaluated in an effort to improve the bond strength and structural properties of the 

resultant cold spray coating. 

The focus of this effort was to demonstrate the feasibility of using the Centerline Cold Spray 

System to repair worn and/or corroded regions on the 7075-T6 aluminum mast support, but it 

should be noted that these areas were considered to be non-structural and did not require the 

stringent qualification testing of structural repairs. For repairs that require higher impact velocity 

and/or alternative coating materials, such as cp-aluminum, 6061 aluminum, or other alloys, it is 

recommended that a stationary cold spray system be used to achieve higher particle velocities. 

The stationary cold spray systems operate with higher gas temperatures and pressures, and also 

have the capability to pre-heat the powder stock, which assists in the consolidation of the 

coating. Higher values of adhesion and a wider variety of coating materials are capable of being 

sprayed with these types of cold spray systems. Additionally, greater deposit efficiencies can 

also be realized. 

 6

Celloto, S. et al. “The Economics of the Cold Spray Process” In The Cold Spray Materials Deposition Process; 

Champagne, V. K., ed.; Woodhead Publishing Limited: Cambridge, 2007. 

 
21

7. Conclusions 

• It is recommended that the Centerline Cold Spray System be considered as a viable means 

to produce aluminum composite coatings to reclaim 7075-T6 aluminum Apache Mast 

Supports in non-structural areas. 

• For repairs that require higher impact velocity and/or alternative coating materials, such as 

6061 aluminum or other alloys, it is recommended that a stationary cold spray system be 

used. 
22

List of Symbols, Abbreviations, and Acronyms 

AMCOM Aviation and Missile Command 

AMRDEC Aviation and Missile Research, Development and Engineering Center 

CP-Al commercially pure aluminum 

ARL U.S. Army Research Laboratory 

ASTM American Society for Testing and Materials 

NSS neutral salt spray testing 

RCB Rotating cantilever beam 

SEM scanning electron microscope 

SPAM Super Plastic Agglomerate Mixing 

SPD Supersonic Particle Deposition 
NO. OF NO. OF 

COPIES ORGANIZATION COPIES ORGANIZATION

23

 1 ADMNSTR 

ELEC DEFNS TECHL INFO CTR 

 ATTN DTIC OCP 

 8725 JOHN J KINGMAN RD STE 0944 

 FT BELVOIR VA 22060-6218 

 1 DARPA 

 ATTN IXO S WELBY 

 3701 N FAIRFAX DR 

 ARLINGTON VA 22203-1714 

 1 CD OFC OF THE SECY OF DEFNS 

 ATTN ODDRE (R&AT) 

 THE PENTAGON 

 WASHINGTON DC 20301-3080 

 1 US ARMY RSRCH DEV AND ENGRG 

 CMND 

 ARMAMENT RSRCH DEV AND 

 ENGRG CTR 

 ARMAMENT ENGRG AND 

 TECHNLGY CTR 

 ATTN AMSRD AAR AEF T J MATTS 

 BLDG 305 

 ABERDEEN PROVING GROUND MD 

 21005-5001 

 1 PM TIMS, PROFILER (MMS-P) 

 AN/TMQ-52 

 ATTN B GRIFFIES 

 BUILDING 563 

 FT MONMOUTH NJ 07703 

 1 US ARMY INFO SYS ENGRG CMND 

 ATTN AMSEL IE TD A RIVERA 

 FT HUACHUCA AZ 85613-5300 

 1 COMMANDER 

 US ARMY RDECOM 

 ATTN AMSRD AMR 

 W C MCCORKLE 

 5400 FOWLER RD 

 REDSTONE ARSENAL AL 35898-5000 

 1 US GOVERNMENT PRINT OFF 

 DEPOSITORY RECEIVING SECTION 

 ATTN MAIL STOP IDAD J TATE 

 732 NORTH CAPITOL ST NW 

 WASHINGTON DC 20402 

 1 US ARMY RESEARCH LAB 

 ATTN RDRL WMM C 

 V CHAMPAGNE 

 ABERDEEN PROVING GROUND MD 

 21005 

 1 US ARMY RSRCH LAB 

 ATTN RDRL CIM G T LANDFRIED 

 BLDG 4600 

 ABERDEEN PROVING GROUND MD 

 21005-5066 

 3 US ARMY RSRCH LAB 

 ATTN IMNE ALC HRR 

 MAIL & RECORDS MGMT 

 ATTN RDRL CIM L TECHL LIB 

 ATTN RDRL CIM P TECHL PUB 

 ADELPHI MD 20783-1197 

TOTAL: 13 (1 ELEC, 1 CD, 11 HCS) 
24

INTENTIONALLY LEFT BLANK.