Crack Repair of Hot Work Tool Steel by Laser Melt Processing

Abstract

Tool steel used in hot work such as die-casting is required to have the resistance to heat checking which results in fine shallow cracking on the part surface. Laser melt processing, which can produce a localized shallow melted zone, has been adapted to repair such kind of cracks. However, the melted zone has a detrimental effect on impact toughness because the laser heating may generate hard structures during the processing. In this paper, the effect of laser melt processing on repairing cracks was evaluated by means of the Charpy impact test and fractography. The test results suggested that when this laser melt processing can eliminate an extensive damaged volume through heat treatment after laser melt processing, the impact toughness is able to recover again to the initial state after heat treatment.