Analysis of cracks produced during carburizing of AISI 1018 steel using a ND:YAG laser

Abstract

Reduced processing time, refined microstructure and low distortion are some of the major advantages of selective carburizing of low carbon steel by using lasers. Formation of cracks in the solidified region, on the other hand, is the major drawback. In the past solidification cracks have been reported in the case of laser melting of grey cast iron, and other iron base alloys, but no detailed study has been reported. The fact that very high carbon contents are introduced by the laser carburizing as compared to that in conventional carburizing, where carbon is limited to 0.80 to 1.0 wt%, lead to a detailed study of laser carburizing. As a part of the ongoing research on carburizing of steel using laser, the authors have investigated cracks formed in the laser carburized zone of AISI 1018 steel. This paper describes a detailed analysis of the cracks formed during laser carburizing. A correlation has been established between the various microstructures formed in laser carburizing, and the affinity of the crack formation. Finally an ideal microstructure has been proposed for the laser carburized layer, which will be most desirable (with respect to crack free and high hardness) in laser carburizing.