Failure Study of 420 Martensitic Stainless Steel Needle Holder with Cr Coating

The failure mechanism of 420 martensitic stainless steel needle holders with a chromium (Cr) coating was investigated. The findings revealed that intergranular fracture occurs in the needle holder due to intergranular corrosion. Moreover, an improper heat treatment process caused the precipitation of numerous M₂₃C₆ Cr-rich nanoparticles along the prior austenite grain boundaries and martensitic lath boundaries, resulting in reduced corrosion resistance in these areas. Additionally, the wear of Cr coating on the surface made the transition area between the jaw and joint of the needle holder susceptible to intergranular corrosion cracking in environments containing chloride. The cracks propagate along the prior austenite grain and martensitic lath boundaries under intergranular corrosion and tensile stress, with some quasi-dissociative and plastic fractures occurring in the late stages of crack propagation. The present study offers theoretical guidance for developing long-life needle holders and ensuring trouble-free service.