The Effect of Processing Variables on Stress-Corrosion Cracking in 9Ni-4Co Steel Alloy.

摘要

The effect of processing variables on SCC,including residual stress and microstructure,was determined for HP 9-4-30 (M) 220/240 KSI,HP 9-4-45 (M) 260/280 KSI,and HP 9-4-45 (B) 260/280 KSI. HP 9-4-30 (M) was immune to SCC except when (1) untempered martensite was present from severe grinding,severe drilling,or welding,or (2) pre-cracked. For tempered martensite the SCC threshold was above 205 KSI,and for untempered martensite the threshold was between 90and 120 KSI. HP 9-4-45 (M) was very susceptible to SCC with all variables except shot peen (immune). For tempered martensite,the SCC threshold was between 89and 127 KSI. HP 9-4-45 (B) was immune to SCC except when cadmium-plated or pre-cracked. Severe grinding and drilling caused SCC in the burn area only. The oxide surface film from 400F thermal cycle (air) during SCC tests gave protection from SCC. Residual surface stress,by X-ray diffraction,was additive to applied stress and had a general relationship to SCC.