Stress Corrosion Cracking Of 17 4 Ph Stainless Steel PDF Download

The susceptibility of 17-4PH to hydrogen-stress cracking was found to increase as the hardness of the steel increased from 42 to 47 R sub c. Conditions of hydrogen-stress cracking were created by attaching a piece of aluminum (7075-T6) to a stress corrosion test specimen. In the absence of aluminum, under identical test conditions, no stress-corrosion cracking failures were recorded in times up to 1000 hr. Charging the bolts with hydrogen and statically loading the bolts in air produced failure times similar to those obtained with the test samples coupled to the aluminum alloy and periodically immersed in a 3-1/2% salt solution. When the 17-4PH was over-aged to a hardness of 40 R sub c or less, the susceptibility was eliminated. These variations in hardness did not change the yield point of the bolt (as determined by the Johnson's 2/3 method). Three additional methods of protection against hydrogen-stress cracking were evaluated: nickel-cadmium electroplating of the bolts, anodizing the aluminum, and insulating with a lubricant at the aluminum/stainless steel interface. Nickel-cadmium plating (AMS-2416) the 17-4PH to a thickness of from 0.2- to 0.4- mil nickel/0.1- to 0.2- mil cadmium offered no resistance to hydrogen-stress cracking. The remaining two methods proved effective in inhibiting hydrogen-stress cracking under controlled laboratory conditions, but, with poor handling procedures, the dissimilar metal couple could be easily activated and cause failure by hydrogen-stress cracking. (Author).