bluuebunny/crossref_metadata_2025 huggingface dataset:
Failure of Supports in a Petrochemical Product Transfer Line
Authors: da Silveira T.L. , Le May I.
Published: May 2019

Leakage was detected at the welds between stiffening plates and the pipe in a transfer line carrying butane and related petrochemical compounds. The line and reinforcing rings were of AISI 316 stainless steel, the pipe being of 508 mm diam and 6.25 mm wall thickness. The design temperature and pressure were 621 deg C and 2.75 kPa, respectively, while the operating conditions were 579 deg C and 1.03 kPa. The line was insulated. Failure occurred after approximately 90,000 h of operation, shutdowns being approximately two per annum. The cracking occurred at the toe of welds between the plates and the pipe. The creep damage failure was attributed to repeated relaxation cycles of very high thermal stresses of resulting from the periodic shutdowns, temperature fluctuations during service, or both. This failure emphasized the information available from an evaluation of the operative creep mechanism, namely grain boundary sliding, relating to the periodic nature of the loading, with high residual stresses being present.
Fracture of a Lifting Fork Arm
Authors: Paul Günter
Published: May 2019

A forged alloy steel arm of a lifting fork with an approximate cross section of 150 x 240 mm (5.92 x 9.45 in.) fractured after only a short service life on a lift truck. The fracture surface had the appearance of a fracture originating from a surface crack. Analysis (visual inspection, 200x micrographs, chemical analysis, and metallographic examination) supported the conclusion that the primary cause of the failure was the brittleness (lack of impact toughness) of the steel. The coarse bainitic microstructure was inadequate for the service application. The microstructure resulted from either improper heat treatment or no heat treatment after the forging operation. The surface cracks in the lifting-fork arm acted as starter notches (stress raisers), assisting in the initiation of fracture. No recommendations were made.
Galvanized Cable Damaged by Localized Heating
Authors: Waldl Elfriede
Published: May 2019

Two sections of a galvanized cable 10.5 A 160 GR +NORM M 9533 (round stranded cable of normal type, h + 6, Langslay, right-handed) were examined. One had a 100 mm long blackish-brown tarnished zone obviously caused by localized heating at one end, inside which the hemp core was missing, and the other corresponded to the original condition of the cable. The cause of the damage was unknown. About a third of the wires had fractured and the rest had been cut. All were tensile fractures with a relatively high degree of necking. The cause of the localized heating was unknown. It can only be concluded from the investigation that the temperature did not exceed the Ac3 point of the wire material, which should be about 750 deg C, and that the heating lasted a fairly long time.
Fractured Chain Link
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A chain link which was part of the hoisting mechanism of a drop hammer broke after three or four months of service. It was reportedly manufactured of the heat resistant steel 30 Cr-Mo-V 9 (Material No. 1.7707). The fracture of the chain link had a conchoidal structure and ran along the austenitic grain boundaries. Such fractures are characteristic results of strong overheating. The coarse-grained, coarse acicular heat-treated structure of the chain link confirmed overheating. Because temperatures in excess of 1150 deg C are required for the solution of impurities, it is more probable that the real damage was done during the heat-up forging (drop-forging) and could not be removed during heat-treatment.
Broken Eyebolt
Authors: Brunsmann Gisela , Szabó Ödön
Published: May 2019

After several years' use, an eyebolt suffered brittle fracture in the first turn of the thread. The fracture started at the notch at the root of the thread. Neither localized material defect nor an old crack were present. The investigation showed that instead of the specified steel quality St 37-2 N, a steel with about 0.5% C had been used. The microstructure with the coarse ferrite network indicated that the forged eye bolt had been normalized either at too high a temperature or not at all. In any case the anneal at 900 deg C produced a considerably more finely grained structure. In addition, the nature of the fracture and the results of the notched bar impact tests showed that in spite of the high C-content, the eye bolt had become brittle as a result of aging.
Fractured Lock Ring of Drum
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

The lock ring of a centrifuge drum was fractured after one year's operation. The ring, with a trapezoidal thread on the inside, was made of steel with approximately 0.5%C-1.3%Mn-1.1%Cr and was hardened and tempered to 105 kp/sq mm strength at 11% elongation (d10). It fractured radially in one of four places in which the cross section was weakened by short grooves that served as tool grips for tightening the cover. The fracture propagated from the base of the thread and followed it in a circumferential direction until it was broken through radially at the top across the ring due to a weakening caused by the external reduction of the cross section. The uppermost turn was corroded at the base by pitting favored by differences in ventilation and formation of Evans elements in the narrow gap between thread and counterthread. Metallographic examination showed that the pitting favored intergranular fissures and therefore it can be established that stress corrosion accelerated cracking of the ring Although since the drum was used for the processing of various liquids, the exact corroding medium cannot be stated.
Broken Inner Rings of Spherical Roller Bearings
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

Inner rings of spherical roller bearings out of full hardening ball bearing steel 100 CrMn 6 (Fe-1C-1.5Cr-1.1Mn, Material No. 1.3520) failed in service. Due to the cracks, parts from the middle flange broke or the rings failed in radial direction completely. All the cracks and fracture originated from the middle flange. In all of the three rings one flank showed heavy wearing and scouring. The cracks started from the edge of this flank with the cylindrical mantle surface of the middle flange. The cracking resembled fatigue cracking. However, in a fine-grained hardened steel such as this, fracture faces due to stress-cracking and overload fracture look the same. Metallographic examination showed the failure of the rings was a result of repeated heating and rapid cooling of the surface due to the grinding of the bearings on one flank of the middle flange. The stress-cracks (grindcracks) spread in steps which finally led to the breaking off of parts from the middle flange and complete failure of the rings.
Broken Helical Compression Spring
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A helical compression spring with ten turns made of 1.8 mm thick wire which was under high pressure during tension applied to a rocker arm broke on the test stand in the third turn. The fracture was a torsion fracture that initiated in the highly loaded inner fiber and showed in its origin the characteristics of a fatigue fracture. A longitudinal fold was located at the fracture crack breakthrough which could still be observed at the fourth and fifth turns, where a further incipient crack originated. A metallographic section was made directly next to the fracture path and the fold was cut. It showed decarburized edges in the outer slanted part and this most likely occurred during rolling. The inner radially proceeding part, however, was probably a fatigue fracture originating in the fold. The fracture of this highly stressed spring was therefore accelerated by a rolling defect. In order to decrease the stress, the construction has meantime been modified.
Wear and Failure of Babbit Bushes in Steam Turbine Sliding Bearings
Authors: Barykin N.P. , Sadykov F.A. , Aslanian I.R.
Published: May 2019

An investigation of wear and failure of babbitt bushes was completed in this study. The results showed that wear at dry sliding of babbitt obtained by plasma spraying was less than that of babbitt in the as-cast state and after a deformation heat treatment. The failure of babbitt bushes was caused by a simultaneous and interrelated exhibition of fatigue and wear processes that depend considerably on cohesion strength between the bush and the bearing base and accumulation of defects on the contact surface between the bush and the shaft.
Coil Spring Failures in Aerospace Hardware
Authors: Frost S. W. , Kamber K. T.
Published: May 2019

Life testing of cyclic loaded, miniature extension springs made of 17-7 PH stainless steel wire and AISI 302 Condition B stainless steel wire has shown end hook configuration to be a major source of weakness. To avoid cracking and subsequent fatigue failure, it was found that stress concentration depended on end hook bend sharpness. Also, interference fits are to be avoided in the end hooks of small springs. Additionally, a need for careful consideration of the stress-corrosion properties of candidate materials for spring applications has been demonstrated by stress-corrosion test results for 17-7 PH CH900 and for Custom 455 CH850 stainless steels. Laboratory testing of these two materials in the form of compression springs confirmed the superiority of the 17-7 PH over Custom 455.
Damage of a Screw in the Seal Coupling
Authors: Kosec B. , Kosec L. , Skraba P. , Bizjan F.
Published: May 2019

The damage to a screw on the head of a 1.8 liter personal car engine was nucleated as the result of common disadvantageous environmental influences and reversed loads leading to corrosion fatigue.
Failure of a Splined Shaft from a Newsprint Plant
Authors: Chan P.C. , Thornley J.C.
Published: May 2019

A splined shaft on a wood chip-to-fiber refiner failed during equipment start-up. The shaft broke into two pieces at a location close to the end of the splined part of the shaft. The failed component showed the classical fatigue-cracking fracture face. The shaft had a diam of approximately 140 mm (5.5 in.) in the unsplined section and was made of 4340 Ni-Cr-Mo alloy steel heat treated to a uniform hardness of HRC 31. Cracks from at least seven different origins had coalesced to produce the single large crack that resulted in failure. The origins of these cracks were on the flanks of the splines. SEM examination revealed the splined shaft failed by fretting fatigue.
Abnormal Wear of a Pinion Gear
Authors: Shah Jivan B.
Published: May 2019

A pinion gear made of AMS 6470 steel, nitrided all over, lost internal splined teeth due to wear. Spline failure of the power turbine gear caused an engine overspeed and disintegration. Excessive spline wear resulted from a new coupling being mated during overhaul with a worn gear spline. Wear on the spline teeth flanks of the coupling was attributed to severe wear on the mating gear (internal) spline teeth. The assigned cause was an inadequate maintenance procedure which resulted in a wear-damaged component being retained in the power train during engine overhaul. To prevent reoccurrence, specific inspection criteria were issued defining maximum limits for spline wear. A procedure and requirements were specified for installing the coupling and pinion gear at the next overhaul.
Corroded Pump Impeller
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

After operating for six months, a pump impeller (of nickel-containing cast iron) showed considerable corrosion. Cross sections showed substantial penetration of the wall thickness without loss of material. The observed supercooled structure implied low strength but would not affect corrosion resistance. Etching of the core structure showed a selective form of cast iron corrosion (spongiosis or graphitic corrosion) which lowered the strength of the cast iron enough that a knife could scrape off a black powder (10.85% C, 1.8% S, 1.45% P). Analysis showed that some of the “sulfate” found in the scrubbing water was actually sulfide (including hydrogen sulfide) and was the main cause of corrosion.
Leaky Heating Coils of an Austenitic Chromium-Nickel-Molybdenum Steel
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A solution containing 50 to 70% calcium chloride (pH 7.5 to 8.5) was concentrated by evaporation in a brick-lined vessel by passing steam at a pressure of 15 atmospheres through a system of heating coils made of austenitic stainless steel X 10 Cr-Ni-Mo-Ti 18 12 (Material No. 1.4573). After five months one of the coils, which consisted of tubes having a wall thickness of 3.4 mm, developed a leak. Tightly closed cracks were seen on the outer surface of the tube. Further tests with color penetration process revealed multiple branched cracks. Longitudinal section showed that the cracks had started from the outside surface of the tube. Electrolytic etching further showed that they had propagated mainly across the grains. It was concluded that this was a typical case of transcrystalline stress corrosion.
Destroyed Screen Bars of Stainless Steel
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

Screens made of stainless steel X5 Cr-Ni-Mo 18 10 (Material No. 1.4401), which were exposed to cooling water from the mouth of a river, became unserviceable after a few months because of the breaking out of parts of the bars. The multiple fracturing of the screen bars in the brackish water of the mouth of the river was attributed to stress corrosion and pitting. The steel used, which contained molybdenum, would have withstood the severe corrosive conditions in the heat-treated condition, i.e. quenched after high temperature anneal. However, the stresses caused by deformation and welding, as well as the intensification of corrosive conditions brought about by design, i.e. creation of corrosion currents in the poorly aerated gaps (Evans elements), made this impossible.
Worn Cast Iron Pump Parts
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A slide and the two guideways of a pump had to be disassembled already during run-in time after approximately 20 h because they had galled completely, before the rated speed of 800 rpm was reached. Chemical analysis of the slide showed the following composition: 3.60C, 3.22Graphite, 2.49Si, 0.51Mn, 0.485P, and 0.112S. The iron was thus distinctly hypereutectic. The galling of the pump parts therefore was favored by an unsuitable structure caused by improper composition and fast cooling. Distortion by casting stresses may have been contributory or may have played the principal part. In order to prevent a repetition, the use of hypoeutectic or eutectic iron, slower cooling of the casting, inoculation of the melt with finely powdered ferrosilicon, and possibly rounding-off the edges or machining of the surfaces are recommended.
Corroded Pipe Section of Oil Burner for Superheated Steam Generator
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A heat exchanger made of a pipe in which oil was heated from the outside from approximately 90 deg C to 170 deg C, by superheated steam of about 8 to 10 atmospheres had developed a leak at the rolled joint of the pipe and pipe bottom. The pipes were supposed to be made from St 35.29 steel and annealed at the rolled joint to 100 mm length. The outer pipe surface was strongly pitted by corrosion all around the rolled joint. In the vicinity of the steam chamber the pipe wall had oxidized through from the exterior to the interior at one spot. Adjoining this spot, grooves caused by erosion were noticeable. This was a typical case of crevice corrosion. The rolled joint evidently was not entirely tight, so that saturated steam condensate could penetrate into the gap.
Spalling Failure of a Spur Gear
Authors: Alban Lester E.
Published: May 2019

A portion of two large spur tooth bull gears made from 4147H Cr-Mo alloy steel that had spalling teeth was submitted for evaluation. The gears were taken from a final drive wheel reduction unit of a very large open-pit mining truck. The parts had met the material and initial heat treat hardening specifications. The mode of failure was tooth profile spalling. By definition, spalling originates at a case/core interface or at the juncture of a hardened/nonhardened area. The cause of this failure was either insufficient or no induction-hardened case along the active profile. The cause was activated by a nonfunctioning induction hardening coil that did not or was not allowed to harden the midprofile of several teeth.
Abrasive Wear Failure of a Hypoid Pinion
Authors: Alban Lester E.
Published: May 2019

A hypoid pinion made from 4820 Ni-Mo alloy steel was the driving member of a power unit operating a rapid transit car. The pinion had been removed from service at the end of the initial test period because it showed undue wear. The mode of failure was severe abrasive wear. The cause of failure was insufficient surface hardness, resulting from improper heat treatment. A service recall for the remaining pinions was immediately initiated.
Failure Analysis of a Radio-Activated Accelerator Component
Authors: Sommer W.F. , Maloy S.A. , James M.R. , Louthan M. , Chen J. , Ullmaier H.
Published: May 2019

A double-walled, hemispherical metal beam exit window made of alloy 718 developed a crack during service, leading to coolant leakage. The window had been exposed to radiation damage from 800 MeV protons and a cyclic stress from 600 MPa tensile to near zero induced by numerous temperature cycles calculated to be from 400 to 30 deg C (752 to 86 deg F). The window was activated to >200 Sv/h. It was determined through analysis using remote handling techniques and hot cells that the crack initiated near a spot weld used to affix thermocouples to the window surface. In addition to analysis of the crack, some of the irradiated material from the window was used to measure mechanical properties. Hot cell techniques for preparation of samples and testing were developed to determine true operating conditions of radiation, strain, and temperature.
Cracking of Sheet Metal
Authors: Aliya D.
Published: May 2019

A crumpled piece of sheet metal had two cracks in a T-junction shape. The relative locations of shear lips in the cracks allowed deduction of which crack happened first, and which direction the cracks propagated.
Corrosion of Gold Bridgewire in Electronic Components
Authors: Downs G. L. , Braun J. D. , Tibbitts E. E.
Published: May 2019

Accelerated aging tests on detonator assemblies, to verify the compatibility of gold bridgewire and Pd-In-Sn solder with the intended explosives, revealed an unusual form of corrosion. The tests, conducted at 74 deg C (165 deg F) and 54 deg C (130 deg F), indicated a preferential attack of the gold. To investigate the problem, a matrix of test units was produced and analyzed. Scanning electron microscopy, EDX analysis, and x-ray diffraction techniques were used to determine the extent of the corrosion and identify the corrosion products. The results indicated that the preferential attack of the gold was due to HCN formed by decomposition of the explosive powder at high temperatures. Other associated reactions were also observed including the subsequent attack of the solder by the gold corrosion product and degradation of the plastic header.
Failure Analysis of Launch Pad Tubing From the Kennedy Space Center
Authors: McDanels S.J.
Published: May 2019

Piping and structural components used in space launch facilities such as NASA's Kennedy Space Center and the Air Force's Cape Canaveral Air Station face extreme operating conditions. Launch effluent and residue from solid rocket boosters react with moisture to form hydrochloric acid that settles on exposed surfaces as they are being subjected to severe mechanical loads imparted during lift-off. Failure analyses were performed on 304 stainless steel tubing that ruptured under such conditions, while carrying various gases, including nitrogen, oxygen, and breathing air. Hydrostatic testing indicated a burst strength of 13,500 psi for the intact sections of tubing. Scanning electron microscopy and metallographic examination revealed that the tubing failed due to corrosion pitting exacerbated by stress-corrosion cracking (SCC). The pitting originated on the outer surface of the tube and ranged from superficial to severe, with some pits extending through 75% of the tube's wall thickness. The SCC emanated from the pits and further reduced the service strength of the component until it could no longer sustain the operating pressure and final catastrophic fracture occurred. Corrosion-resistant coatings added after the investigation have proven effective in preventing subsequent such failures.
Corrosion of Steel Pipe in a Heating and Cooling System
Authors: Khan A.H.
Published: May 2019

A shopping mall in South Carolina was originally constructed in 1988 and a second phase completed in 1989. The HVAC system inside the mall included an open, recirculating condenser water loop that served various fan coil units located within tenant spaces. The system had a recirculating capacity of about 44,000 gal (166,000 L) of water. It consisted primarily of steel pipes fitted with threaded connectors on the 2 in. (46 cm) pipes and bolted flanged couplings on the larger pipes. Seven years following the completion of the mall, corrosion problems were noted at the outer and inner surfaces of the pipe. Visual observations on the inner diametral surfaces revealed that the pipes were, in almost all cases, filled with corrosion products. A significant amount of base metal loss was documented in all of the samples. The cause of the observed corrosion was determined to be a lack of corrosion monitoring and poor water quality. Pipe replacement and a regular water testing program were recommended.
Failure Analysis of a Reduction Furnace Heat Resistant Roll
Authors: Milner R.D.
Published: May 2019

A failure analysis was conducted in late 1996 on two rolls that had been used in the production of iron and steel powder. The rolls had elongated over their length such that the roll trunnions had impacted with the furnace wall refractory. The result was distortion and bowing of the roll bodies which necessitated their removal from service. The initial analysis found large quantities of nitrogen had been absorbed by the roll shell. Further research indicated nitrogen pickup accounted for 3% volumetric growth for every 1% by weight nitrogen absorption. This expansion was sufficient to account for the dimensional change observed in the failed rolls. This paper details the failure analysis and resulting research it inspired. It also provides recommendations for cast material choice in highly nitriding atmospheres.
Creep Rupture of a Carbon Steel Furnace Tube
Authors: Ogden Paul
Published: May 2019

A carbon steel furnace tube which should have given good service for ten years ruptured after one year. The tube showed obvious swelling at the point of rupture, and the bulged surface of the tube was oxidized at a temperature far above the design temperature. There was little or no loss in wall thickness due to corrosion or scaling, and the tube wall was thinned to a knife edge at the rupture. Metallographic examination showed the condition of the material was satisfactory. The failure was mechanical in nature, typical of short time creep rupture. The localized oxidation indicated improper furnace operation or blockage of the tube. The furnace was checked and found to have a burner tip out of order. After the tip was repaired, localized overheating was minimized and further premature failures did not occur.
Fractures of Electro-Galvanized Cylinderhead Screws
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

Eight cylinderhead screws cracked after a short running time in motors. They were made of Fe-0.45C-1Cr steel, had rolled threads, were heat treated to 110 kg/sq mm tensile strength, and were electrolytically galvanized. All fractured at the root of the thread. The surfaces of fracture were fine-grained and had not spread by rubbing. Because the screws were electrolytically galvanized, failure resulted from “delayed fracture.” Experience has shown that this type of fracture is seen on production parts made of high-strength steels, which absorbed hydrogen during pickling or during a galvanic surface treatment. Such parts will rupture below the elastic limit during continuous stressing. This often occurs only after the expiration of a certain time period, and preferably at locations of stress concentrations such as changes in cross section or threads. As a rule, the hydrogen cannot be verified analytically because most of it escapes again after prolonged storage at room temperature or short heating at 100 to 200 deg C.
Broken Slide of a Friction Press
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A short fracture section of a forged and normalized Ck 35 (DIN 17200) steel slide showed three distinct zones: a dark colored crystalline area, an incipient crack propagating into a far advanced, rubbed fracture surface, and a fine crystalline final break. Metallographic examination showed the dark incipient crack was present before the last heat treatment and was oxidized and decarburized prior to the conclusion of the annealing process. The crack ran perpendicular to the fiber, so it was not formed before or during forging. It was a thermal stress crack produced during flame cutting of the middle section of the slide. The initial crack acted as a sharp notch favoring the formation of the fatigue fracture which lead to the failure of the slide.
Metal Waves or Laking on Zinc-Based Diecastings
Authors: Perger Gustav R. , Robinson Peter M.
Published: May 2019

Lakes in zinc die castings are areas encompassed by irregular lines or waves on flat or slightly contoured surfaces which are intended to look uniform. The laked areas have to be removed by polishing before the castings can be plated. This adds considerably to the overall cost of production. Castings examined were of an automobile name-plate holder with two flat sides of approximately 113 sq cm. All castings produced during a trial showed laking defects, the number and position varying from casting to casting. It was found that formation of metal waves and lakes depended primarily on the design of the gate and runner system and operating conditions. High flow efficiencies, with adequate feeding to all sections of the die, and short cavity fill times are desirable.
Leaky Socket Pipe from the Safety Return Circuit of a Heating Installation
Authors: Kauczor Egon
Published: May 2019

An elbow made from welded steel tube had become leaky along a well-defined line in the axial direction. The entire wall of the tube was corroded, and the longitudinally-welded seam stood out clearly as a result of particularly intensive corrosive attack. The appearance of the corroded surface indicates the action of water with a high oxygen content. The oxygen in the return water must have originated from the ventilation of the open expansion vessel. Because of the corrosion-favoring effect of a crevice, water with a high oxygen-content that was perhaps still warm or even hot found particularly favorable conditions for corrosion in the defective welded seam (crevice corrosion). The tube material itself is perfectly satisfactory and in no way responsible for the failure.
Decarburization
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

Decarburization of steel may occur as skin decarburization by gases either wet or containing oxygen, and as a deep ongoing destruction of the material by hydrogen under high pressure. Guidelines are given for recognizing decarburization and determining at what point cracks occurred. How decarburization changes workpiece properties and the case of hydrogen decarburization are addressed through examples.
Cast Ingot Cracked During Forging
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

An octagonal steel ingot weighing 13 tons made of manganese-molybdenum steel developed gaping cross-cracks on all eight sides in the forging press during initial pressure application. It was reported that the steel had been melted in a basic 12-ton arc furnace, oxygenated, furnished with 42 kg of 75% ferrosilicon and 12 kg aluminum additions, alloyed with 160 kg of 80% ferromanganese, and finally deoxidized in the ladle with 42 kg calcium silicon. For metallographic examination a plate approximately 100 mm thick was cut parallel to one of the eight planes. Platelet-like particles could be discerned on the conchoidal fracture planes with the SEM. The precipitates proved to be thin and partially transparent platelets of a hexagonal crystal lattice whose parameters resemble those of AIN. The precipitates were at least in part still undissolved in spite of the long holding period at high initial forging temperature. Another block melted under the same conditions and immediately after the defective one, was forged into a gear ring without any trouble. This ring was free of grain boundary precipitates, but it contained only 0.012 % AI and 0.0102 % N.
Primary Grain Boundary Cracks in Cast Ingots and Flaky Crankshafts
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

Octagonal cast ingots weighing 6.5 tons and made of unalloyed heat treated steel CK 45 according to DIN 17200, and crankshafts forged from these ingots showed internal separations during ultrasonic testing. To determine the cause of defect, an ingot slice and a crank arm were examined metallographically. Investigation showed this was a case where flaky forgings were made from cast ingots with primary grain boundary cracks. This parallelity supports the often expressed opinion that both occurrences have the same origin, i.e. that hydrogen precipitation was the driving force in the formation of primary grain boundary cracks in cast ingots.
Poorly Drawable Steel Wire for Ball Bearings
Authors: Naumann Friedrich Karl , Spies Ferdinand
Published: May 2019

A drawing plant which processed steel wire of designation 105 Cr 2 for ball bearings had losses due to crack formation and wire breakage during drawing. To establish the reason for the breakage, seven fractures were submitted for investigation with contiguous wire segments on both sides of the fracture of 300 mm each. Missing in the lamellar surface structure, with the exception of the remnants of a coarse network, were the pre-eutectically precipitated carbides to be expected in this steel. Surrounding the ferritic region in the surface structure, a ring of lamellar pearlite is seen, which turns into the granular annealed structure towards the core. The described structural phenomena were noted in all of the seven fracture regions. Their intensity always decreased with increasing distance from the fracture. Surface decarburization caused the formation of lamellar pearlite during annealing. This investigation further revealed that the localized decarburization and pearlite formation was present already in the rolled wire in uneven distribution over the entire coil length.
Plating Adherence Problems in Electronic Components
Authors: Kumar Arun
Published: May 2019

Electroless nickel plating separation from copper alloy CDA175 retaining clips used on printed circuit boards was caused by a copper oxide layer that reduced adhesion of the nickel plating on the clips. Stresses that developed during module insertion caused flaking to occur at the oxidized copper surface. Electroless nickel plating separation from OFHC copper leads was caused by improper handling rather than a plating anomaly per se. Tin plating separation from copper underplating on a hybrid package lid occurred because of a four-week delay between the copper plating and tin plating steps. It was recommended that tin plating should follow the copper underplating within 24 h and a cleaning step of bright dipping after copper plating be performed.
Failure Analysis of an Aluminum Casting
Authors: Medeiros Steven C.
Published: May 2019

In the EMD-2 Joint Directed Attack Munition (JDAM), the A357 aluminum alloy housing had been redesigned and cast via permanent mold casting, but did not meet the design strength requirements of the previous design. Mechanical tests on thick and thin sections of the forward housing assembly revealed tensile properties well below the allowable design values. Radiology and CT evaluations revealed no casting defects. Optical microscopy revealed porosity uniformly distributed throughout the casting on the order of 0.1 mm pore diam. Scanning electron microscopy revealed elongated pores, which indicated turbulent filling of the mold. Spherical pores would have indicated the melt had been improperly degassed. Based on these findings, it was recommended that the manufacturer analyze and redesign the gating system to eliminate the turbulent flow problem during the permanent mold casting process.
Structural Instability of Cold Worked Alloy 304 in 650 °C Service
Authors: Krafft H.
Published: May 2019

A heavily worked 304 stainless steel wire basket recrystallized and distorted while in service at 650 deg C (1200 deg F). This case study demonstrates that heavily cold worked austenitic stainless steel components can experience large losses in creep strength, and potentially structural collapse, under elevated temperature service, even at temperatures more than 300 deg C (540 deg F) below the normal solution annealing temperature. The creep strength of the recrystallized 304/304L steel was more than 1000 times less than that achievable with solution annealed 304H. These observations are consistent with limitations (2000 Addendum to ASME Boiler and Pressure Vessel Code) on the use of cold worked austenitic stainless steels for elevated temperature service.
An Analysis of Fiber-Induced Surface Defects in Electroless Plated Components
Authors: Mehta S. , Vysotskaya A. , Mistry N.
Published: May 2019

The paper discusses the analysis of a coating defect on a high phosphorus electroless nickel (Ni-11 wt. % P) deposit plated on an aluminum alloy substrate. Preliminary investigations had indicated that the elongated defects were possibly caused by the entrapment of long fibers or particles during the plating. The possible sources of fibers were identified. The SEM/EDS analysis of fibers collected from the air duct filters correlated very well with the defect shape and the EDS profile collected from under the defect site. It appears that the fibers from air duct filters directly above the plating line were blown into the plating tank and getting co-deposited. The paper describes the step-by-step analysis of the defect that led to successful identification of the root cause of the defect.
An Investigation of the Development of Defects During Flow Forming of High Strength Thin Wall Steel Tubes
Authors: Rajan K.M. , Narasimhan K.
Published: May 2019

Flow forming technology has emerged as a promising, economical metal forming technology due to its ability to provide high strength, high precision, thin walled tubes with excellent surface finish. This paper presents experimental observations of defects developed during flow forming of high strength SAE 4130 steel tubes. The major defects observed are fish scaling, premature burst, diametral growth, microcracks, and macrocracks. This paper analyzes the defects and arrives at the causative factors contributing to the various failure modes.
Discoloration of a Stainless Steel Tube after Pickling
Authors: Suess S.J.
Published: May 2019

A type 17-4PH stainless steel tube exhibited brown discoloration after a pickling operation. EDS analysis of the extracted substance revealed relatively high levels of iron and chromium, along with lower amounts of aluminum, silicon, sulfur, chlorine, calcium, manganese, and nickel. The iron, chromium, and nickel are likely in the form of dissolution products from the pickling solution. FTIR analysis revealed the presence of polypropylene and poly(ethylene:propylene). The EDS results showed that the discoloration of the tube was associated with oxidation products of the tube material, as well as adherent organic residue. Analysis by FTIR of the residue revealed detectable levels of two polymeric substances, which were later determined to be construction materials of the pickling tank. It was recommended that more frequent cleaning and/or replacement of the pickling solution be put into place and another type of tank material be considered.
Tinting of Electropolished Copper Parts
Authors: Suess S.J.
Published: May 2019

A large number of electropolished copper parts showed evidence of discoloration (tinting) after electropolishing. Because these parts are used in a high-vacuum application, even trace amounts of organic materials would be problematic. Scanning electron microscopy of nondiscolored and discolored areas both showed trace amounts of residue in the form of adherent deposits. EDS, FTIR spectroscopy, XPS, and secondary ion mass spectroscopy (SIMS) analyses indicated that the discoloration to the copper components was due to the development of CuO at localized regions. It was recommended that process changes be made to completely remove residual processing fluids from the part surfaces before electropolishing. The use of more aggressive detergents was suggested, and it was recommended also that a filtering and recirculating system be considered for use in the cleaning and electropolishing tanks.
Plating Blemishes in Zinc Die Castings
Authors: Aliya D.
Published: May 2019

Near-surface porosity in zinc die castings that were subsequently plated with copper, nickel, and bright chromium was causing blemishes in the plating. Identifying die casting turbulence and hot spots were keys to process modifications that subsequently allowed porosity to be greatly minimized.
Carbon Steel Heat Treating Problems
Authors: Aliya D.
Published: May 2019

A plant had manufactured and heat treated their product in house for years. As time went on, the special steel that they had been using became more expensive, and a switch was made to a more common and less highly alloyed material. However, no change in hardness specifications were made, because calculations of ideal critical diameter and analysis of available hardenability data indicated that the original hardness specification could be met. There was, however, less room for process variation. The parts ended up containing temper carbides, developed heavy decarburization, and experienced excessive distortion because they were left in the furnace for extended and varying periods with the temperature “turned down a couple hundred degrees.”
Investigation of Cracking and Erratic Behavior of the Uranium-Titanium Alloy
Authors: Bird E. L.
Published: May 2019

The U-0.8wt%Ti alloy is often used in weapon applications where high strength and fairly good ductility are necessary. Components are immersion quenched in water from the gamma phase to produce a martensitic structure that is amenable to aging. Undesirable conditions occur when a component occasionally cracks during the quenching process, and when tensile specimens fail prematurely during mechanical testing. These two failures prompted an investigative analysis and a series of studies to determine the causes of the cracking and erratic behavior observed in this alloy. Quench-related failures whereby components that cracked either during or immediately after the heat treatment/quenching operation were sectioned for metallographic examination of the microstructure to examine the degree of phase transformation. Examination of premature tensile specimen failures by scanning electron microscopy and X-ray imaging of fracture surfaces revealed pockets of inclusions at the crack origins. In addition, tests were conducted to evaluate the detrimental effects of internal hydrogen on ductility and crack initiation in this alloy.
Plug Weld Defects in Low-Carbon Steel Bomb Fins
Authors: Pepi M.
Published: May 2019

Welded low-carbon steel bomb fins were rejected because of poor weld practice. Visual and metallographic examination revealed that the resistance plug welds that attach the outer skin to the inner spar displayed inadequate weld penetration. Recommended changes to the resistance welding parameters resulted in acceptable welds.
Use of Electron Fractography to Diagnose Cracking in a Chromium-Plated AISI 4340 Pivot Bolt
Authors: Scott James A.
Published: May 2019

Overhaul mechanics discovered a crack in an AISI 4340 Cr-Mo-Ni alloy steel pivot bolt when grinding off the chromium plating. The bolt had served for an estimated 10,000 h and was replated when last overhauled. On checking the bolt, several fine cracks were found on the surface. A 6500x micrograph revealed the intergranular nature of a crack. By trying different grinding procedures, investigators were able to reproduce this type of failure in the laboratory. It was concluded that grinding cracks initiated the failure. It should be noted that governing specifications prohibit grinding on high-strength steel; chromium should be stripped by electrochemical methods.
Evaluating Component Failures: The Cure Can Be Worse Than the Illness
Authors: Suss Henry
Published: May 2019

The presence of secondary, branching intergranular stress-corrosion cracking in a type 440C stainless bearing caused the analyst to overlook the real culprit, which was a mechanically-initiated, primary transgranular crack that propagated through the steel's hard chromium carbide. Failure was actually caused by overload. Had the original conclusion been accepted, a relatively exotic alloy would have been specified. In another case, brass heat exchanger tube failure was automatically attributed to attack by an acidic cleaner, and a decision was made to stop using the solution. A more thorough analysis showed failure was caused by tube vibration. In a third case, a type 304 stainless steel bellows in a test loop was thought to have failed because of chloride stress corrosion. The report concluded with a recommendation that carbon steel be used as an alternative bellows material. Caustic, not chloride, stress corrosion was the culprit. Had material substitutions been made on the original premise of countering chloride stress corrosion, most of the loop's highly stressed components would have eventually failed.
Problematic Failure Analysis of a Cast Steel Crankshaft
Authors: Moore D.A. , Packer K.F. , Jones A.J. , Carlson D.M.
Published: May 2019

This case study involves two continuously cast steel crankshaft failures. Three parties performed their own failure analyses: (1) the engine manufacturer responsible for component design, specification, and application; (2) the steel supplier and forging supplier responsible for making the steel, forging the shape, and preliminary heat treatment; and (3) a supplier that provided induction hardening, finish machining, and inspection. An independent engineering firm was subsequently involved, but because each party had its own agenda, there was no agreement on the metallurgical source of the failure and thus no continued analysis to pin down and eliminate the root cause.
Failure of a Fairground Ride
Authors: Crosky A.
Published: May 2019

On 22 Feb 1997, one of the arms on an amusement park ride became detached from the central pylon, allowing the passenger carriage at the end of the arm to fall to the ground. Detachment of the arm was found to have occurred as a result of fracture of the cast steel bearing cap and the retaining bolt, which then allowed the axle to move out of its housing. The cap material was a cast 0.25% carbon steel. The retaining bolt failed in the threaded region, with no evidence of fatigue. One of the reinforcing straps welded to the outer surface of the cap had also fractured as the result of fatigue. Evidence of a weld repair could be seen at the location of the fracture. The bearing cap, cap 2L, failed by fatigue initiated from the corners of the two threaded holes. One of the two reinforcing straps then failed by overload, while the second one became detached by fracturing through the welds. The bolt then failed by overload. The cracking in cap 2L was not an isolated occurrence. Cracking was detected at the same location in almost all the other caps on the same device. The cracking had been in progress for considerable time. To prevent the reoccurrence of such a failure, recommendations are given for a more-rigorous inspection protocol.
Failure of Large Tantalum Heat Exchanger During Transportation to Site
Authors: Blum M. E.
Published: May 2019

A steam heated exchanger was designed for concentrating sulfuric acid. Tantalum was selected for the tubing and the tube sheet liner because of its outstanding corrosion resistance. However, although the exchanger passed a searching shop inspection, it leaked during site testing. Considerable argument ensued about whether the cracking observed was due to poor welding during fabrication, or through abuse during handling on site. An SEM examination of the fractures revealed high cycle, low amplitude fatigue, and the problem was traced to vibration during road transport. Further failures were avoided by improved design and packing. This paper illustrated the value of SEM fractography when a rapid investigation is needed under the pressures of a fast moving project.
Metallurgical Examinations of a Fragmented Blank Firing Adapter and Associated Components from an M-16 Rifle
Authors: Gray R. J. , Houck C. W.
Published: May 2019

Personnel responsible for laboratory protection at some plants are required to participate in exercises simulating a breach of security at the site. This document reports a metallurgical investigation of blank firing adapters (BFA), one of which exploded during such a training exercise. Determination of the cause of the explosion was the primary objective of the examination. Metallographic studies included the examination of BFAs fabricated from two different types of alloys that were tested for shock reaction. Optical microscopy supported by electron microscopy and analytical methods were used. Our investigation supports the supposition that a live round of ammunition was inadvertently fired.
Failure of Propeller Attachment Bolts
Authors: Craft C. Howard
Published: May 2019

The propeller from a small private airplane came off in flight. The head ends of all six attachment bolts remained in the propeller hub when it was found. Two threaded shanks with nuts remained with the engine, while the remaining four shank ends with their nuts were missing. Parts available for examination, in addition to the hub and attachment bolts, were the two propeller blades and the engine crankshaft. The purpose of this examination was to determine the nature and probable cause of failure in the six attachment bolts. Indications of fatigue failure and wear were the major findings in visual and low power microscopic examination. Fracture surfaces indicated failure was initiated in the threads in four bolts and in the shanks in two. The group of four bolts failed primarily due to tensile loads, while the other two bolts failed primarily due to bending loads. It was concluded that failure was due to improper installation torqueing of the bolts.