Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c9001012
P. Ogden
An interstage radiator gas coil began leaking after only 45 days of service. The original brass coil with several aluminum fins was replaced three times but each replacement lasted less than a day. After removing the fins, leaks were found at circumferential cracks. A section of a tube was removed and split, revealing a series of cracks, evenly spaced. Crack spacing coincided with fin spacing, indicating that stresses incurred during installation of the fins promoted failure. Metallographic examination showed intergranular, branched cracking, characteristic of stress corrosion failures, with the cracks starting on the inside surfaces of the tubes. There was no known corrosive agent in the system, and no other corrosion damage could be found. Qualitative tests and spectrographic analysis gave a positive indication for mercury. The spacing of the cracks, the branched intergranular cracking, the rapid failure, and presence of mercury led to the conclusion of stress-corrosion cracking. It was impossible to remove mercury from the system so carbon steel coils were substituted for the brass ones. The carbon steel coils gave failure-free service for over nine years.
{"title":"Stress-Corrosion Cracking of a Brass Radiator Coil","authors":"P. Ogden","doi":"10.31399/asm.fach.modes.c9001012","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c9001012","url":null,"abstract":"\u0000 An interstage radiator gas coil began leaking after only 45 days of service. The original brass coil with several aluminum fins was replaced three times but each replacement lasted less than a day. After removing the fins, leaks were found at circumferential cracks. A section of a tube was removed and split, revealing a series of cracks, evenly spaced. Crack spacing coincided with fin spacing, indicating that stresses incurred during installation of the fins promoted failure. Metallographic examination showed intergranular, branched cracking, characteristic of stress corrosion failures, with the cracks starting on the inside surfaces of the tubes. There was no known corrosive agent in the system, and no other corrosion damage could be found. Qualitative tests and spectrographic analysis gave a positive indication for mercury. The spacing of the cracks, the branched intergranular cracking, the rapid failure, and presence of mercury led to the conclusion of stress-corrosion cracking. It was impossible to remove mercury from the system so carbon steel coils were substituted for the brass ones. The carbon steel coils gave failure-free service for over nine years.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131062946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c9001537
E. A. Lauchner, R. E. Herfert
After completing a fatigue test of an aluminum alloy component machined from a 7079-T6 forging, technicians noted a 5 in. crack which ran longitudinally above and through the flange. When the fracture face was examined by light microscopy, observers could not ascertain the exact mode of fracture. Electron fractography revealed that five different modes of crack growth were operative as the part failed. Region 1 was a shallow zone (about 0.002 in. at its deepest) of dimpled structure typical of an overload failure. Region 2 was a zone that grew by a stress corrosion mechanism. Through a fatigue mechanism was operative in Region 3, it was not the cause of the large crack. Region 4, which covered 50% of the fracture area, developed mainly by stress corrosion. This zone gradually changed into the combination of intergranular and transgranular overload in Region 5, which covered approximately the remaining 50% of the fracture. Apparently, after stress corrosion moved halfway through, the part failed by overload. This failure analysis proved that a crack, originally thought to be a fatigue failure, was actually a stress corrosion crack.
{"title":"Electron Fractography Pinpoints Cause of Fatigue Fracture","authors":"E. A. Lauchner, R. E. Herfert","doi":"10.31399/asm.fach.modes.c9001537","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c9001537","url":null,"abstract":"\u0000 After completing a fatigue test of an aluminum alloy component machined from a 7079-T6 forging, technicians noted a 5 in. crack which ran longitudinally above and through the flange. When the fracture face was examined by light microscopy, observers could not ascertain the exact mode of fracture. Electron fractography revealed that five different modes of crack growth were operative as the part failed. Region 1 was a shallow zone (about 0.002 in. at its deepest) of dimpled structure typical of an overload failure. Region 2 was a zone that grew by a stress corrosion mechanism. Through a fatigue mechanism was operative in Region 3, it was not the cause of the large crack. Region 4, which covered 50% of the fracture area, developed mainly by stress corrosion. This zone gradually changed into the combination of intergranular and transgranular overload in Region 5, which covered approximately the remaining 50% of the fracture. Apparently, after stress corrosion moved halfway through, the part failed by overload. This failure analysis proved that a crack, originally thought to be a fatigue failure, was actually a stress corrosion crack.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114710763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c0006417
A cadmium-plated 4340 Ni-Cr-Mo steel ballast elbow assembly was submitted for failure analysis to determine the element or radical present in an oxidation product found inside the elbow assembly. Energy-dispersive x-ray analysis in the SEM showed that iron was the predominant species, presumably in an oxide form. The inside surface had the appearance of typical corrosion products. Hardness measurements indicated that the 4340 steel was heat treated to a strength of approximately 862 MPa (125 ksi). It was concluded that the oxide detected on the ballast elbow was iron oxide. The possibility that the corrosion products would eventually create a blockage of the affected hole was great considering the small hole diameter (4.2 mm, or 0.165 in.). It was recommended that a quick fix to stop the corrosion would be to apply a corrosion inhibitor inside the hole. This, however, would cause the possibility of inhibitor buildup and the eventual clogging of the hole. A change in the manufacturing process to include a cadmium plating on the hole inside surface was recommended. This was to be accomplished in accordance with MIL specification QQ-P-416, Type II, Class 1. A material change to 300-series stainless steel was also recommended.
提交了一个镀镉的4340镍铬钼钢压载弯头组件进行故障分析，以确定在弯头组件内发现的氧化产物中存在的元素或自由基。扫描电镜的能量色散x射线分析表明，铁是主要的物质，可能以氧化物形式存在。内表面具有典型腐蚀产物的外观。硬度测量表明，4340钢经过热处理，强度约为862 MPa (125 ksi)。结果表明，在压载弯头上检测到的氧化物为氧化铁。考虑到小孔直径(4.2 mm, 0.165 in.)，腐蚀产物最终堵塞受影响孔的可能性很大。建议快速解决腐蚀问题的方法是在井内施用缓蚀剂。然而，这可能会导致抑制剂积聚，最终导致井眼堵塞。建议改变制造工艺，在孔内表面镀上镉。这是按照MIL规范q - p -416, II型，1类来完成的。还建议将材料更换为300系列不锈钢。
{"title":"Corrosion of a Ballast Gas Elbow Assembly","authors":"","doi":"10.31399/asm.fach.modes.c0006417","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0006417","url":null,"abstract":"\u0000 A cadmium-plated 4340 Ni-Cr-Mo steel ballast elbow assembly was submitted for failure analysis to determine the element or radical present in an oxidation product found inside the elbow assembly. Energy-dispersive x-ray analysis in the SEM showed that iron was the predominant species, presumably in an oxide form. The inside surface had the appearance of typical corrosion products. Hardness measurements indicated that the 4340 steel was heat treated to a strength of approximately 862 MPa (125 ksi). It was concluded that the oxide detected on the ballast elbow was iron oxide. The possibility that the corrosion products would eventually create a blockage of the affected hole was great considering the small hole diameter (4.2 mm, or 0.165 in.). It was recommended that a quick fix to stop the corrosion would be to apply a corrosion inhibitor inside the hole. This, however, would cause the possibility of inhibitor buildup and the eventual clogging of the hole. A change in the manufacturing process to include a cadmium plating on the hole inside surface was recommended. This was to be accomplished in accordance with MIL specification QQ-P-416, Type II, Class 1. A material change to 300-series stainless steel was also recommended.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"130 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116887851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c0047332
Deterioration of the vanes and a wearing away of the area surrounding the mainshaft-bearing housing of the pump bowl for a submersible water pump used in a well field were noticed during a maintenance inspection. The bowl was sand cast from gray iron and had been in service approximately 45 months. Visual examination of the vanes and the area surrounding the mainshaft-bearing housing revealed a dark corrosion product that was soft, porous, and of low mechanical strength. There were areas with severe erosion. Macrographs of sections through the pump shell and a vane showed darker areas representing graphitic residue and corrosion products that were not removed by erosion. Exposure of the pump bowl to the well water resulted in graphitic corrosion, which generated a soft, porous graphitic residue impregnated with insoluble corrosion products. Failure of the pump bowl resulted from the continuous erosion of the residue by action of the water within the pump.
{"title":"Failure of a Gray Iron Pump Bowl Because of Graphitic Corrosion from Exposure to Well Water","authors":"","doi":"10.31399/asm.fach.modes.c0047332","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0047332","url":null,"abstract":"\u0000 Deterioration of the vanes and a wearing away of the area surrounding the mainshaft-bearing housing of the pump bowl for a submersible water pump used in a well field were noticed during a maintenance inspection. The bowl was sand cast from gray iron and had been in service approximately 45 months. Visual examination of the vanes and the area surrounding the mainshaft-bearing housing revealed a dark corrosion product that was soft, porous, and of low mechanical strength. There were areas with severe erosion. Macrographs of sections through the pump shell and a vane showed darker areas representing graphitic residue and corrosion products that were not removed by erosion. Exposure of the pump bowl to the well water resulted in graphitic corrosion, which generated a soft, porous graphitic residue impregnated with insoluble corrosion products. Failure of the pump bowl resulted from the continuous erosion of the residue by action of the water within the pump.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"441 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123426338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c9001446
A 2 ft. diam 20 ft. long cylinder with a wall thickness of 1 in. used for the transportation of a compressed gas failed by cracking. The cylinder was forged in a low ally steel. The working pressure was 3000 psi and it had been in service for about seven years. A longitudinal crack, about 2 in. long, developed at the approximate mid-length of the vessel, and allowed slow de-pressurization. Subsequent examination by radiography and ultrasonic means indicated the crack was associated with an irregularly shaped, laminar type of defect located within the wall of the vessel. It was concluded that failure of this vessel resulted from the development of a radial crack orientated in the axial direction. This appeared to have originated on the bore surface in a region where the laminar defect closely approached this surface. The defect was introduced during the manufacture of the vessel, probably originating as a secondary pipe in the ingot which was subsequently displaced and forced into the wall of the vessel during the piercing operation.
{"title":"Failure of a Large Gas Cylinder Due to Internal Laminar Defects","authors":"","doi":"10.31399/asm.fach.modes.c9001446","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c9001446","url":null,"abstract":"\u0000 A 2 ft. diam 20 ft. long cylinder with a wall thickness of 1 in. used for the transportation of a compressed gas failed by cracking. The cylinder was forged in a low ally steel. The working pressure was 3000 psi and it had been in service for about seven years. A longitudinal crack, about 2 in. long, developed at the approximate mid-length of the vessel, and allowed slow de-pressurization. Subsequent examination by radiography and ultrasonic means indicated the crack was associated with an irregularly shaped, laminar type of defect located within the wall of the vessel. It was concluded that failure of this vessel resulted from the development of a radial crack orientated in the axial direction. This appeared to have originated on the bore surface in a region where the laminar defect closely approached this surface. The defect was introduced during the manufacture of the vessel, probably originating as a secondary pipe in the ingot which was subsequently displaced and forced into the wall of the vessel during the piercing operation.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128663782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c0047199
The lower receiver of the M16 rifle is an anodized forging of aluminum alloy 7075-T6. Degradation of the receivers was observed after three years of service in a hot, humid atmosphere. The affected areas were those in frequent contact with the user's hands. There was no question that the material failed as a result of exfoliation corrosion, so an investigation was undertaken, centered around the study of thermal treatments that would increase the exfoliation resistance and still develop the required 448 MPa (65 ksi) yield strength. The results of the study concluded that rolled bar stock should be preferred to extruded bar stock. Differences in grain structure of the forgings, as induced by differences in thermal-mechanical history of the forged material, can have a significant effect on susceptibility to exfoliation corrosion. Regarding thermal treatment, the results show conclusively that large changes in strength and exfoliation characteristics of 7075 forgings can be induced by changes in temperature or time of thermal treatment. With regard to the effect of quenching rate on exfoliation characteristics, a cold-water quench below 25 deg C (75 deg F) would appear to be far superior to an elevated-temperature quench to minimize exfoliation for 7075 forgings in the T6 temper.
{"title":"Failure of Rifle Receivers Caused by Exfoliation","authors":"","doi":"10.31399/asm.fach.modes.c0047199","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0047199","url":null,"abstract":"\u0000 The lower receiver of the M16 rifle is an anodized forging of aluminum alloy 7075-T6. Degradation of the receivers was observed after three years of service in a hot, humid atmosphere. The affected areas were those in frequent contact with the user's hands. There was no question that the material failed as a result of exfoliation corrosion, so an investigation was undertaken, centered around the study of thermal treatments that would increase the exfoliation resistance and still develop the required 448 MPa (65 ksi) yield strength. The results of the study concluded that rolled bar stock should be preferred to extruded bar stock. Differences in grain structure of the forgings, as induced by differences in thermal-mechanical history of the forged material, can have a significant effect on susceptibility to exfoliation corrosion. Regarding thermal treatment, the results show conclusively that large changes in strength and exfoliation characteristics of 7075 forgings can be induced by changes in temperature or time of thermal treatment. With regard to the effect of quenching rate on exfoliation characteristics, a cold-water quench below 25 deg C (75 deg F) would appear to be far superior to an elevated-temperature quench to minimize exfoliation for 7075 forgings in the T6 temper.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129915412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c0092103
A polyoxymethylene gear wheel that had been in operation in a boiler room failed. Investigation (visual inspection and 305x images) supported the conclusion that failure was due to postcrystallization causing considerable shrinkage. Breakdown along the crystalline superstructure started mainly at the mechanically stressed tooth flanks. In addition, oil vapors, humidity, and other degradative agents could also have contributed to the observed failure. No recommendations were made.
{"title":"Failure of a Polyoxymethylene Gear Wheel","authors":"","doi":"10.31399/asm.fach.modes.c0092103","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0092103","url":null,"abstract":"\u0000 A polyoxymethylene gear wheel that had been in operation in a boiler room failed. Investigation (visual inspection and 305x images) supported the conclusion that failure was due to postcrystallization causing considerable shrinkage. Breakdown along the crystalline superstructure started mainly at the mechanically stressed tooth flanks. In addition, oil vapors, humidity, and other degradative agents could also have contributed to the observed failure. No recommendations were made.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116626171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c0092102
A nylon oil-lubricated driving gear showed pitting upon visual inspection. The pitting produced numerous surface microcracks. Further investigation (visual inspection and 37x images) supported the conclusion that failure occurred in association with large-scale fragmentation (frictional wear). No recommendations were made.
{"title":"Failure of a Nylon Driving Gear","authors":"","doi":"10.31399/asm.fach.modes.c0092102","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0092102","url":null,"abstract":"\u0000 A nylon oil-lubricated driving gear showed pitting upon visual inspection. The pitting produced numerous surface microcracks. Further investigation (visual inspection and 37x images) supported the conclusion that failure occurred in association with large-scale fragmentation (frictional wear). No recommendations were made.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121588506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c9001177
F. Naumann, F. Spies
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.
将含有50%至70%氯化钙(pH值为7.5至8.5)的溶液在砖内衬容器中蒸发浓缩，蒸汽在15个大气压下通过由奥氏体不锈钢x10cr - ni - mo - ti 1812(材料号1.4573)制成的加热盘管系统。五个月后，其中一个由壁厚为3.4毫米的管子组成的线圈出现了泄漏。管的外表面有紧密闭合的裂缝。进一步的彩色渗透试验发现了多个分支裂纹。纵断面显示，裂纹是从管的外表面开始的。电解蚀刻进一步表明，它们主要在晶粒间传播。结果表明，这是典型的跨晶应力腐蚀。
{"title":"Leaky Heating Coils of an Austenitic Chromium-Nickel-Molybdenum Steel","authors":"F. Naumann, F. Spies","doi":"10.31399/asm.fach.modes.c9001177","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c9001177","url":null,"abstract":"\u0000 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.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127565282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c0046991
The outlet-piping system of a steam-reformer unit failed by extensive cracking at four weld locations. The welded system consisted of Incoloy 800 (Fe-32Ni-21Cr-0.05C) pipe and fittings. The exterior surfaces of the system were insulated with rock wool that did not contain weatherproofing. On-site visual examination and magnetic testing indicated severe external corrosion of most of the piping. The system showed extensive cracking in weld HAZ. One specimen indicated that corrosion extended to a depth of 3.2 mm and cracks were seen at the edge of the cover bead and in the HAZ of the weld. Metallographic examination showed that cracking was intergranular and that adjacent grain boundaries had undergone deep intergranular attack. Examination at higher magnification revealed heavy carbide precipitation, primarily at grain boundaries, indicating that the alloy had been sensitized, which resulted from heating during welding. Electron probe x-ray microanalysis showed the outside surface of the tube did not have the protective chromium oxide scale normally found on Incoloy 800. The inside surface of the tube had a thin chromium oxide protective scale. This evidence supported the conclusions that the deep oxidation greatly decreased the strength of the weld HAZ and cracking followed.
{"title":"Failure of an Incoloy 800 Piping System","authors":"","doi":"10.31399/asm.fach.modes.c0046991","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0046991","url":null,"abstract":"\u0000 The outlet-piping system of a steam-reformer unit failed by extensive cracking at four weld locations. The welded system consisted of Incoloy 800 (Fe-32Ni-21Cr-0.05C) pipe and fittings. The exterior surfaces of the system were insulated with rock wool that did not contain weatherproofing. On-site visual examination and magnetic testing indicated severe external corrosion of most of the piping. The system showed extensive cracking in weld HAZ. One specimen indicated that corrosion extended to a depth of 3.2 mm and cracks were seen at the edge of the cover bead and in the HAZ of the weld. Metallographic examination showed that cracking was intergranular and that adjacent grain boundaries had undergone deep intergranular attack. Examination at higher magnification revealed heavy carbide precipitation, primarily at grain boundaries, indicating that the alloy had been sensitized, which resulted from heating during welding. Electron probe x-ray microanalysis showed the outside surface of the tube did not have the protective chromium oxide scale normally found on Incoloy 800. The inside surface of the tube had a thin chromium oxide protective scale. This evidence supported the conclusions that the deep oxidation greatly decreased the strength of the weld HAZ and cracking followed.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127813072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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