Surface normalization of sensitized stainless steel by laser surface melting

Abstract

A scanning laser beam was used to melt and normalize the surface layer of sensitized 304 stainless steel. Subsequent Strauss tests indicated a complete resistance to intergranular corrosion. Mechanical testing at strains less than 15% also showed laser surface melting to indefinitely extend specimen life in a stress corrosion environment. At strains greater than 15%, the laser-scanned protective layer was breached by cracks. A maximum critical laser-scanning velocity compatible with normalization of the surface layer is calculated. Similarly, a minimum critical laser-scanning velocity required to avoid resensitization is determined. The stress distribution in a 304 stainless-steel specimen with a laser-melted and self-quenched surface layer is estimated and shown to be compatible with the observed appearance of martensite in the melted surface layer.