Study of Stress Corrosion Cracking Susceptibility of Type 316L Stainless Steel In Vitro

Abstract

Post-failure analyses of Type 316L stainless steel implants have frequently implicated stress corrosion cracking as the mode of failure. If stress corrosion cracking of this stainless steel is likely in vivo, this material would have questionable utility for such applications. However, this material is widely used by manufacturers and approved by government regulating agencies. This study was designed to critically evaluate this issue. No susceptibility to stress corrosion cracking of 316L was found in manufactured implants or in specimens from implant quality material in vitro by both static loading and slow strain rate testing techniques. An adjunct in vitro fatigue study disclosed multiple fatigue cracks with branching tendencies. It is concluded that crack branching and secondary cracking in 316L implants are not adequate indicia of stress corrosion cracking of implants.

Stainless Steels for Implants

“…This study also determined that little difference exists in the slow strain rate stress corrosion cracking of these alloys in de-ionized distilled water and Ringers solution at 371C when no stress concentrator is present. This research is supported by previous studies in the same area by other investigators (18)(19)(20). Other investigators have suggested that SCC may occur in vivo at temperatures well below the generally accepted threshold for these alloys in chloride solutions of 601C because of the complexity of the in vivo environment (21).…”