Type 410 stainless steel bolts were used to hold together galvanized gray cast iron splice case halves. Before installation, the bolts were treated with molybdenum disulfide (MoS 2 ) antiseize compound. Several failures of splice case bolts were discovered in flooded manholes after they were in service for three to four months. Laboratory experiments were conducted to determine if the failure mode was hydrogen-stress cracking, if sulfides accelerate the failure, if heat treatment can improve the resistance against this failure mode, and if the type 305 austenitic stainless steel would serve as a replacement material. Based on test results, the solution to the hydrogen-stress cracking problem consisted of changing the bolt from type 410 to 305 stainless steel, eliminating use of MoS2, and limiting the torque to 60 N·m (540 in.·lb).

Cadmium-coated type 410 martensitic stainless steel 1 4 -14 self-drilling tapping screws fractured during retorquing tests within a few weeks after installation. The screws were used to assemble structural steel frames for granite panels that formed the outer skin of a high-rise building. Fractographic and metallographic examination showed that the fractures occurred in a brittle manner from intergranular crack propagation. Laboratory and simulated environmental tests showed that an aqueous environment was necessary for the brittle fracture/cracking phenomenon. The cracks were singular and intergranular with little branching. Secondary subsurface cracks suggested possible hydrogen embrittlement. The 410 screws had been introduced to replace conventional case-hardened carbon steel screws that conform to SAE specification J78. Carbon steel screws had a proven record of acceptable performance for the intended application. It was recommended that use of the 410 screws be discontinued in preference to the case-hardened carbon steel screws.

During installation, a clamp-strap assembly, specified to be type 410 stainless steel-austenitized at 955 to 1010 deg C (1750 to 1850 deg F), oil quenched, and tempered at 565 deg C (1050 deg F) for 2 h to achieve a hardness of 30 to 35 HRC, and used for securing the caging mechanism on a star-tracking telescope, fractured transversely across two rivet holes closest to one edge of the pin retainer in a completely brittle manner. Comparison with a non-failed strap using microscopic examination, spectrographic analysis, and slow-bend tests showed that both fit the 410 stainless steel specs, but hardness and grain size were different. Reheat treatment of full-width specimens showed that coarse grain size (ASTM 2 to 3) was responsible for the brittle fracture, and excessively high temperature during austenitizing caused the large grain size in the failed strap. The fact that the hardness of the strap that failed was lower than the specified hardness of 30 to 35 HRC had no effect on the failure because that of the non-failed strap was even lower. Recommendation was that the strap should be heat treated as specified to maintain the required ductility and grain size.

A wall section of a carbon steel choke body in gas service at 4400 psig blew out three months after the use of a corrosion inhibitor was stopped. Corrosion damage occurred in ripples, leaving both smoothly polished and unattacked areas. The corrodent in condensate wells was principally carbon dioxide dissolved in water condensed from the gas stream, with organic acids possibly an aggravating factor. A gas analysis showed no other corrosive agents. No metallurgical or fabrication defects were found in the carbon steel part. The mode of attack was corrosion-erosion, caused by the corrosive, high velocity gas flow. The corrosion rate of either the inhibited or uninhibited gas stream was too high for equipment in high pressure gas service. Type 410 (12% Cr) stainless steel was recommended for the choke bodies because other equipment such as valves made of type 410 showed no evidence of corrosion damage after three years' exposure. This change was made five years ago and there have been no failures since.

To ensure no malfunctions and although there were no apparent problems, a main fuel control was returned to the factory for examination after service on a test aircraft engine that had experienced high vibrations. When the fuel control was disassembled, a lever, cast from AMS 5350 (AISI type 410) stainless steel that was through-hardened to 26 to 32 HRC and passivated, was shown to be cracked. The crack initiated at the sharp corner of the elongated milled slot and propagated across to the outer wall. The sections around the crack were spread about 30 deg apart, showing the fracture surface under investigation had beach marks initiating at the sharp corner along the milled slot. Changes in frequency or amplitude of vibration caused different rates of propagation, resulting in a change in pattern. This evidence supported the conclusion that the lever failed in fatigue as a result of excessive vibration of the fuel control on the test engine. Recommendations included redesign of the lever with a large radius in the corner where cracking originated. This would reduce the stress-concentration factor significantly, thus minimizing the susceptibility of the lever to fatigue.

A lever (machined from a casting made of AISI type 410 stainless steel, then surface hardened by nitriding) that was a component of the main fuel-control linkage of an aircraft engine fractured in flight after a service life of less than 50 h. Investigation (radiographic inspection) supported the conclusions that the lever broke at a cold shut extending through approximately 95% of the cross section. The normally applied load constituted an overload of the remainder of the lever. Recommendations included adding magnetic-particle inspection to the inspection procedures for this cast lever.

Stainless steel bolts broke after short-term exposure in boiler feed-pump applications. Specifications required that the bolts be made of a 12% Cr high-strength steel with a composition conforming to that of AISI type 410 stainless steel. Several bolts from three different installations were examined. It was found that fracture of the bolts was by intergranular stress corrosion. A metallic copper-containing antiseizure compound on the bolts in a corrosive medium set up an electro-chemical cell that produced trenchlike fissures or pits for fracture initiation. Because the bolts were not subjected to cyclic loading, fatigue or corrosion fatigue was not possible. To prevent reoccurrence, bolts were required to conform to the specified chemical composition. The hardness range for the bolts was changed from 35 to 45 HRC to 18 to 24 HRC. Petroleum jelly was used as an antiseizure lubricant in place of the copper-containing compound. As a result of these changes, bolt life was increased to more than three years.

AISI type 410 stainless steel tube bundles in a heat exchanger experienced leakage during hydrostatic testing even before being in service. The inside surfaces of the tubes was observed to have been pitted. Chloride-ion pitting was revealed by the undercutting in the cross section of a pit and further confirmed by x-ray spectrometry. It was concluded that the failure was caused by pitting due to chlorides in the water used to flush the tubes before service. The use of brackish water to flush or test stainless steel equipment was recommended to avoid pitting.