Effect of CrxCy–NiCr coating on the hydrogen embrittlement of 17-4 PH stainless steel using the smooth bar tensile test

A Cr x C y –NiCr cermet coating was fabricated using the supersonic plasma spray technique, and its effect on the hydrogen embrittlement of 17-4 PH stainless steel was studied through electrochemical hydrogen charging and slow strain rate tensile testing. The index of hydrogen embrittlement susceptibility was calculated, and the results show that the Cr x C y –NiCr coating plays a significant role in preventing hydrogen embrittlement cracking. The hydrogen content analysis demonstrates that the Cr x C y –NiCr coating enhances the resistance to hydrogen embrittlement by acting as a hydrogen diffusion barrier. This effect is mainly due to the Cr x C y ceramics in the cermet coating having a very low hydrogen diffusion rate. In addition, the strength and ductility of the specimen without the coating decrease gradually with increasing hydrogen charging current density. According to the tensile testing results and the fracture surface analysis, the hydrogen embrittlement phenomenon is explained by a mixed mechanism involving hydrogen-enhanced local plasticity and hydrogen-enhanced decohesion.