Pub Date : 2019-06-01DOI: 10.31399/asm.fach.modes.c9001712
R. Milner
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.
{"title":"Failure Analysis of a Reduction Furnace Heat Resistant Roll","authors":"R. Milner","doi":"10.31399/asm.fach.modes.c9001712","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c9001712","url":null,"abstract":"\u0000 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.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"42 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":"125137841","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.c0046476
A fused-salt electrolytic-cell pot containing a molten eutectic mixture of sodium, potassium, and lithium chlorides and operating at melt temperatures from 500 to 650 deg C (930 to 1200 deg F) exhibited excessive corrosion after two months of service. The pot was a welded cylinder with 3-mm thick type 304 stainless steel walls and was about 305 mm (12 in.) in height and diam. Analysis (visual inspection and 500x micrographs etched with CuCl2) supported the conclusions that the pot failed by intergranular corrosion because an unstabilized austenitic stainless steel containing more than 0.03% carbon had been sensitized and placed in contact in service with a corrosive medium at temperatures in the sensitizing range. Recommendations included changing material for the pot from type 304 stainless steel to Hastelloy N (70Ni-17Mo-7Cr-5Fe). Maximum corrosion resistance and ductility are developed in Hastelloy N when the alloy is solution heat treated at 1120 deg C (2050 deg F) and is either quenched in water or rapidly cooled in air. An alternative, but less suitable, material for the pot was type 347 (stabilized grade) stainless steel. After welding, the 347 should be stress relieved at 900 deg C (1650 deg F) for 2 h and rapidly cooled to minimize residual stresses.
{"title":"Intergranular Corrosion of a Type 304 Stainless Steel Fused-Salt Pot Due to Sensitization","authors":"","doi":"10.31399/asm.fach.modes.c0046476","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0046476","url":null,"abstract":"\u0000 A fused-salt electrolytic-cell pot containing a molten eutectic mixture of sodium, potassium, and lithium chlorides and operating at melt temperatures from 500 to 650 deg C (930 to 1200 deg F) exhibited excessive corrosion after two months of service. The pot was a welded cylinder with 3-mm thick type 304 stainless steel walls and was about 305 mm (12 in.) in height and diam. Analysis (visual inspection and 500x micrographs etched with CuCl2) supported the conclusions that the pot failed by intergranular corrosion because an unstabilized austenitic stainless steel containing more than 0.03% carbon had been sensitized and placed in contact in service with a corrosive medium at temperatures in the sensitizing range. Recommendations included changing material for the pot from type 304 stainless steel to Hastelloy N (70Ni-17Mo-7Cr-5Fe). Maximum corrosion resistance and ductility are developed in Hastelloy N when the alloy is solution heat treated at 1120 deg C (2050 deg F) and is either quenched in water or rapidly cooled in air. An alternative, but less suitable, material for the pot was type 347 (stabilized grade) stainless steel. After welding, the 347 should be stress relieved at 900 deg C (1650 deg F) for 2 h and rapidly cooled to minimize residual stresses.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"74 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":"124277438","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.c0046422
Stator vanes (cast from a Cu-Mn-Al alloy) in a hydraulic dynamometer used in a steam-turbine test facility were severely eroded. The dynamometer was designed to absorb up to 51 MW (69,000 hp) at 3670 rpm, and constituted an extrapolation of previous design practices and experience. Its stator was subject to severe erosion after relatively short operating times and initially required replacement after each test program. Although up to 60 cu cm (3.7 cu in.) of material was being lost from each vane, it only reduced the power-absorption capacity by a small amount. Analysis supported the conclusion that the damage was due to liquid erosion, but it could not be firmly established whether it was caused by cavitation or by liquid impact. Recommendations included making a material substitution (to Mo-13Cr-4Ni stainless steel) and doing a redesign to reduce susceptibility to erosion as well as erosion-producing conditions.
{"title":"Liquid Erosion of Hydraulic Dynamometer Stator Vanes","authors":"","doi":"10.31399/asm.fach.modes.c0046422","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0046422","url":null,"abstract":"\u0000 Stator vanes (cast from a Cu-Mn-Al alloy) in a hydraulic dynamometer used in a steam-turbine test facility were severely eroded. The dynamometer was designed to absorb up to 51 MW (69,000 hp) at 3670 rpm, and constituted an extrapolation of previous design practices and experience. Its stator was subject to severe erosion after relatively short operating times and initially required replacement after each test program. Although up to 60 cu cm (3.7 cu in.) of material was being lost from each vane, it only reduced the power-absorption capacity by a small amount. Analysis supported the conclusion that the damage was due to liquid erosion, but it could not be firmly established whether it was caused by cavitation or by liquid impact. Recommendations included making a material substitution (to Mo-13Cr-4Ni stainless steel) and doing a redesign to reduce susceptibility to erosion as well as erosion-producing conditions.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"54 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":"128614002","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.c0048361
Several failures occurred in 64-mm schedule 80 type 304 stainless steel (ASME SA-312, grade TP304) piping in a steam-plant heat-exchanger system near tee fittings at which cool water returning from the heat exchanger was combined with hot water from a bypass. Various portions of the piping were subjected to temperatures ranging from 29 to 288 deg C. Each of the failures were revealed to consist of transgranular cracking in and/or close to the circumferential butt weld joining the tee fitting to the downstream pipe leg, where the hot bypass water mixed with the cool return water. The transgranular cracks suggested that thermal fatigue was a more likely cause of failure than SCC. It was concluded by temperature measurements that circumferential temperature gradients, in combination with inadequate flexibility in the piping system as a whole, had caused the failures. The tee fitting was redesigned to alleviate the thermal stress pattern.
{"title":"Low-Cycle Thermal Fatigue Failure of a Type 304 Stainless Steel Tee Fitting","authors":"","doi":"10.31399/asm.fach.modes.c0048361","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0048361","url":null,"abstract":"\u0000 Several failures occurred in 64-mm schedule 80 type 304 stainless steel (ASME SA-312, grade TP304) piping in a steam-plant heat-exchanger system near tee fittings at which cool water returning from the heat exchanger was combined with hot water from a bypass. Various portions of the piping were subjected to temperatures ranging from 29 to 288 deg C. Each of the failures were revealed to consist of transgranular cracking in and/or close to the circumferential butt weld joining the tee fitting to the downstream pipe leg, where the hot bypass water mixed with the cool return water. The transgranular cracks suggested that thermal fatigue was a more likely cause of failure than SCC. It was concluded by temperature measurements that circumferential temperature gradients, in combination with inadequate flexibility in the piping system as a whole, had caused the failures. The tee fitting was redesigned to alleviate the thermal stress pattern.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"8 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":"125280886","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.c0046535
One of five underground drain lines intended to carry a highly acidic effluent from a chemical-processing plant to distant holding tanks failed in just a few months. Each line was made of 304L stainless steel pipe 73 mm (2 in.) in diam with a 5 mm (0.203 in.) wall thickness. Lengths of pipe were joined by shielded metal arc welding. Soundness of the welded joints was determined by water back-pressure testing after several lengths of pipe had been installed and joined. Before completion of the pipeline, a pressure drop was observed during back-pressure testing. An extreme depression in the backfill revealed the site of failure. Analysis (visual inspection, electrical conductivity, and soil analysis) supported the conclusions that the failure had resulted from galvanic corrosion at a point where the corrosivity of the soil was substantially greater than the average, resulting in a voltage decrease near the point of failure of about 1.3 to 1.7 V. Recommendations included that the pipelines be asphalt coated and enclosed in a concrete trough with a concrete cover. Also, magnesium anodes, connected electrically to each line, should be installed at periodic intervals along their entire length to provide cathodic protection.
{"title":"Failure of a Buried Type 304L Stainless Steel Drain Line by Galvanic Attack","authors":"","doi":"10.31399/asm.fach.modes.c0046535","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0046535","url":null,"abstract":"\u0000 One of five underground drain lines intended to carry a highly acidic effluent from a chemical-processing plant to distant holding tanks failed in just a few months. Each line was made of 304L stainless steel pipe 73 mm (2 in.) in diam with a 5 mm (0.203 in.) wall thickness. Lengths of pipe were joined by shielded metal arc welding. Soundness of the welded joints was determined by water back-pressure testing after several lengths of pipe had been installed and joined. Before completion of the pipeline, a pressure drop was observed during back-pressure testing. An extreme depression in the backfill revealed the site of failure. Analysis (visual inspection, electrical conductivity, and soil analysis) supported the conclusions that the failure had resulted from galvanic corrosion at a point where the corrosivity of the soil was substantially greater than the average, resulting in a voltage decrease near the point of failure of about 1.3 to 1.7 V. Recommendations included that the pipelines be asphalt coated and enclosed in a concrete trough with a concrete cover. Also, magnesium anodes, connected electrically to each line, should be installed at periodic intervals along their entire length to provide cathodic protection.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"1 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":"122010850","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.c0091096
A 4340 steel shaft, the driving member of a large rotor subject to cyclic loading and frequent overloads, broke after three weeks of operation. The driving shaft contained a shear groove at which the shaft should break if a sudden high overload occurred, thus preventing damage to an expensive gear mechanism. The rotor was subjected to severe chatter, which was an abnormal condition resulting from a series of continuous small overloads occurring at a frequency of around three per second. Investigation (visual inspection, hardness testing, and hot acid etch images) supported the conclusion that the basic failure mechanism was fracture by torsional fatigue, which started at numerous surface shear cracks, both longitudinal and transverse, that developed in the periphery of the root of the shear groove. These shear cracks resulted from high peak loads caused by chatter. The shear groove in the shaft had performed its function, but at a lower overload level than intended. Recommendations included increasing the fatigue strength of the shaft by shot peening the shear groove to minimize chatter.
{"title":"Torsional-Fatigue Fracture of a Large 4340 Steel Shaft That Was Subject to Cyclic Loading and Frequent Overloads","authors":"","doi":"10.31399/asm.fach.modes.c0091096","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0091096","url":null,"abstract":"\u0000 A 4340 steel shaft, the driving member of a large rotor subject to cyclic loading and frequent overloads, broke after three weeks of operation. The driving shaft contained a shear groove at which the shaft should break if a sudden high overload occurred, thus preventing damage to an expensive gear mechanism. The rotor was subjected to severe chatter, which was an abnormal condition resulting from a series of continuous small overloads occurring at a frequency of around three per second. Investigation (visual inspection, hardness testing, and hot acid etch images) supported the conclusion that the basic failure mechanism was fracture by torsional fatigue, which started at numerous surface shear cracks, both longitudinal and transverse, that developed in the periphery of the root of the shear groove. These shear cracks resulted from high peak loads caused by chatter. The shear groove in the shaft had performed its function, but at a lower overload level than intended. Recommendations included increasing the fatigue strength of the shaft by shot peening the shear groove to minimize chatter.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"78 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":"127873629","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.c0091336
A type 304 austenitic stainless steel tube (0.008 max C, 18.00 to 20.00 Cr, 2.00 max Mn, 8.00 to 10.50 Ni) was found to be corroded. The tube was part of a piping system, not yet placed in service, that was exposed to an outdoor marine environment containing chlorides. As part of the assembly, a fabric bag containing palladium oxide was taped to the tube. The palladium served as a “getter.” Investigation (visual inspection and EDS analysis of corrosion debris) supported the conclusion that chlorides and palladium both contributed to corrosion in the crevice created by the tape on the tube, which was periodically exposed to water. Recommendations included taking steps to prevent water from entering and being trapped in this area of the assembly.
发现304型奥氏体不锈钢管(0.008 max C, 18.00 ~ 20.00 Cr, 2.00 max Mn, 8.00 ~ 10.50 Ni)被腐蚀。该管道是管道系统的一部分，尚未投入使用，暴露在含有氯化物的室外海洋环境中。作为组装的一部分，一个含有氧化钯的布袋被粘在管子上。钯起到“吸气剂”的作用。调查(目视检查和腐蚀碎片的EDS分析)支持这样的结论:氯化物和钯都导致了管道上的胶带形成的裂缝腐蚀，管道定期暴露在水中。建议包括采取措施防止水进入和被困在大会的这个区域。
{"title":"Crevice Corrosion on Stainless Steel Tube","authors":"","doi":"10.31399/asm.fach.modes.c0091336","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0091336","url":null,"abstract":"\u0000 A type 304 austenitic stainless steel tube (0.008 max C, 18.00 to 20.00 Cr, 2.00 max Mn, 8.00 to 10.50 Ni) was found to be corroded. The tube was part of a piping system, not yet placed in service, that was exposed to an outdoor marine environment containing chlorides. As part of the assembly, a fabric bag containing palladium oxide was taped to the tube. The palladium served as a “getter.” Investigation (visual inspection and EDS analysis of corrosion debris) supported the conclusion that chlorides and palladium both contributed to corrosion in the crevice created by the tape on the tube, which was periodically exposed to water. Recommendations included taking steps to prevent water from entering and being trapped in this area of the assembly.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"28 2 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":"132637204","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.c9001165
F. Naumann, F. Spies
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.
{"title":"Corroded Pump Impeller","authors":"F. Naumann, F. Spies","doi":"10.31399/asm.fach.modes.c9001165","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c9001165","url":null,"abstract":"\u0000 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.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"13 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":"127809220","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.c0047879
The stub-shaft assembly which was part of the agitator shaft in a polyvinyl chloride reactor, fractured in service after a nut that retained a loose sleeve around the smaller-diam section of the shaft had been tightened several times to reduce leakage. The shaft was made of ASTM A105, grade 2 steel, and the larger-diam section was covered with a type 316 stainless steel end cap. The cap was welded to each end using type ER316 stainless steel filler metal. The forged steel shaft was revealed to have fractured at approximately 90 deg to the shaft axis in the weld metal and not in the heat-affected zone of the forged steel shaft. Microscopic investigation and chemical analysis of the steel shaft revealed presence of martensite (offered a path of easy crack propagation) around the fusion line and dilution of the weld metal by the carbon steel shaft. The microstructure was found to be martensitic as the fusion line was approached. The forged steel shaft was concluded to have failed by ductile fracture and possible reasons were discussed. Corrective measures adopted in the replacement shaft were specified.
{"title":"Ductile Fracture of a Forged Steel Shaft at a Change in Section and at a Stainless Steel Weld","authors":"","doi":"10.31399/asm.fach.modes.c0047879","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0047879","url":null,"abstract":"\u0000 The stub-shaft assembly which was part of the agitator shaft in a polyvinyl chloride reactor, fractured in service after a nut that retained a loose sleeve around the smaller-diam section of the shaft had been tightened several times to reduce leakage. The shaft was made of ASTM A105, grade 2 steel, and the larger-diam section was covered with a type 316 stainless steel end cap. The cap was welded to each end using type ER316 stainless steel filler metal. The forged steel shaft was revealed to have fractured at approximately 90 deg to the shaft axis in the weld metal and not in the heat-affected zone of the forged steel shaft. Microscopic investigation and chemical analysis of the steel shaft revealed presence of martensite (offered a path of easy crack propagation) around the fusion line and dilution of the weld metal by the carbon steel shaft. The microstructure was found to be martensitic as the fusion line was approached. The forged steel shaft was concluded to have failed by ductile fracture and possible reasons were discussed. Corrective measures adopted in the replacement shaft were specified.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"52 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":"126615393","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.c0046418
Equipment in which an assembly of in-line cylindrical components rotated in water at 1040 rpm displayed excessive vibration after less than one hour of operation. The malfunction was traced to an aluminum alloy 6061-T6 combustion chamber that was part of the rotating assembly. Analysis (visual inspection, 100x/500x/800x micrographic examination, spectrographic analysis, and hardness testing) supported the conclusions that, as a result of improper heat treatment, the combustion-chamber material was too soft for successful use in this application. Misalignment of the combustion chamber and one or both of the mating parts resulted in eccentric rotation and the excessive vibration that caused malfunction of the assembly. Irregularities in the housing around the combustion chamber and temperature variation relating to the combustion pattern in the chamber were considered to be possible contributing factors to localization of the cavitation erosion. Recommendations included adopting inspection procedures to ensure that the specified properties of aluminum alloy 6061-T6 were obtained and that the combustion chamber and adjacent components were aligned within specified tolerances. In a similar situation, consideration should also be given to raising the pressure in the coolant in order to suppress the formation of cavitation bubbles.
{"title":"Cavitation Erosion of a Water-Cooled Aluminum Alloy 6061-T6 Combustion Chamber","authors":"","doi":"10.31399/asm.fach.modes.c0046418","DOIUrl":"https://doi.org/10.31399/asm.fach.modes.c0046418","url":null,"abstract":"\u0000 Equipment in which an assembly of in-line cylindrical components rotated in water at 1040 rpm displayed excessive vibration after less than one hour of operation. The malfunction was traced to an aluminum alloy 6061-T6 combustion chamber that was part of the rotating assembly. Analysis (visual inspection, 100x/500x/800x micrographic examination, spectrographic analysis, and hardness testing) supported the conclusions that, as a result of improper heat treatment, the combustion-chamber material was too soft for successful use in this application. Misalignment of the combustion chamber and one or both of the mating parts resulted in eccentric rotation and the excessive vibration that caused malfunction of the assembly. Irregularities in the housing around the combustion chamber and temperature variation relating to the combustion pattern in the chamber were considered to be possible contributing factors to localization of the cavitation erosion. Recommendations included adopting inspection procedures to ensure that the specified properties of aluminum alloy 6061-T6 were obtained and that the combustion chamber and adjacent components were aligned within specified tolerances. In a similar situation, consideration should also be given to raising the pressure in the coolant in order to suppress the formation of cavitation bubbles.","PeriodicalId":231268,"journal":{"name":"ASM Failure Analysis Case Histories: Failure Modes and Mechanisms","volume":"145 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":"116410454","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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