Quantifying Heat-Affected Zone Hydrogen-Induced Cracking in High-Strength Naval Steels

The implant test was used to compare a recently developed blast-resistant steel (BA-160) to two existing naval steels, HY-100 and HSLA-100, in order to assess potential susceptibility to heat-affected zone (HAZ) hydrogen-induced cracking (HIC). Based on the implant test results of applied tensile stress vs. time to failure, the lower critical stress (LCS), normalized critical stress ratio (NCSR), and embrittlement index (El) were determined in order to make a quantitative comparison. In all cases, failure during implant testing occurred in the coarse-grained HAZ (CGHAZ). The microstructure of the CGHAZ was characterized using optical and transmission electron microscopy. It was found that martensite is the predominant microstructural feature in the CGHAZ of BA-160 and HY-100, while a mixture of martensite and bainite are observed in HSLA-100. The fracture behavior was characterized and related to microstructure and cracking susceptibility. Based on both NCSR and El values, it can be concluded that BA-160 is more susceptible to HAZ HIC compared to HSLA-100, but more resistant than HY-100.