Microstructural Changes in Electroplated Chromium Coating–Substrate Interfaces Induced by Shot Peening

Abstract

Shot peening has been widely used for industrial field because of its attractive effects to increase strength of treated material. In addition, microstructural changes induced by shot peening have been recent interest since they possibly promise adding surface functions and enhancing the surface characteristics. In this study, shot peening was conducted on electroplated chromium coatings deposited on carbon steel substrate in order to create mechanically-mixed microstructure which was composed of iron and chromium. Microstructural changes induced by shot peening was carefully analyzed under ranging peening time. Results indicated that shot peening using steel grit particles created specific microstructure where fragments of chromium plating were dispersed into steel matrix whereas shot peening using spherical shot insufficiently induced the microstructural changes. It was implied that fragments of chromium plating were transported from top surface to steel substrate interior and simultaneously pulverized due to continuous impact of the particles during shot peening process. Severe plastic deformation induced at the shot-peened surface played as a driving force to induce material transportation and resulting “composite” microstructure formation.