Ferrite effects on the hydrogen embrittlement of 17-4PH stainless steel

Purpose The purpose of this study is to investigate the effect of ferrite on hydrogen embrittlement (HE) of the 17-4PH stainless steels. Design/methodology/approach The effects of ferrite on HE of the 17-4PH stainless steels were investigated by observing microstructure and conducting slow-strain-rate tensile tests and hydrogen permeability tests. Findings The microstructure of the ferrite-bearing sample is lath martensite and banded ferrite, and the ferrite-free sample is lath martensite. After hydrogen charging, the plasticity of the two steels is significantly reduced, along with the tensile strength of the ferrite-free sample. The HE susceptibility of the ferrite-bearing sample is significantly lower than the ferrite-free steel, and the primary fracture modes gradually evolved from typical dimple to quasi-cleavage and intergranular cracking. After aging at 480 degrees C for 4 h and hydrogen charging for 12 h, the 40.9% HE susceptibility of ferrite-bearing samples was the lowest. In addition, the hydrogen permeation tests show that ferrite is a fast diffusion channel for hydrogen, and the ferrite-bearing samples have higher effective hydrogen diffusivity and lower hydrogen concentration. Originality/value There are a few studies of the ferrite effect on the HE properties of martensitic precipitation hardening stainless steel.

Automated summary

This study investigated the effect of ferrite on the hydrogen embrittlement of 17-4PH stainless steels. By observing microstructure and conducting slow-strain-rate tensile tests and hydrogen permeability tests, it was found that the ferrite-bearing samples exhibited significantly lower hydrogen embrittlement susceptibility compared to the ferrite-free steel.