Phase transformation of austempered and quench-tempered gray cast irons under laser surface hardening treatment

ABSTRACT In this research, the effects of laser surface hardening treatment on the phase transformation of austempered and quench-tempered grey cast irons were investigated. It was found that there were four zones in the matrix of austempered grey cast iron and three zones in the matrix of quench-tempered grey cast iron produced by the laser hardening process. Both cast irons had central laser-hardened zones containing ledeburite (Zone 1) and heat-affected zones (Zone 2) containing martensite. For austempering, an additional heat-affected zone (Zone 3) consisting of tempered ausferrite and a substrate (Zone 4) consisting of ausferrite was formed in the matrix, the dimensions of the laser-hardened and heat-affected regions were independent of the austempering and tempering temperatures. The results reported in this work could be used as a valuable reference for future research on laser-hardened grey cast iron applications. For quench tempering, the substrate (Zone 4) consisted of tempered martensite. Additionally