Surface Modification of Cold Working Die Steel, SKD11, using Laser Irradiation

Abstract

At present, cold working die steel, SKD11, is commonly being used as a material for metal molds due to its superior wear and corrosion resistance properties. However, it is difficult to obtain die steel SKD11 with a mirror-finished surface during metal mold manufacturing, because of the coarse-grained carbides present in the base metal. In this study, laser surface modification with melting has been proposed to improve the surface finish of SKD11 as a new surface modification method. In this method, coarse-grained carbides can be decomposed by melting the surface layer using a laser beam. As a result, the carbides containing coarse grains in the surface layer can be completely decomposed into their elements by laser beam irradiation to the surface. Both the compositions and crystalline structure in the modified region are entirely uniform, and the laser irradiated material could be polished easily to obtain a mirror-finished surface using alumina as an abrasive. Moreover, the reflectivity of light from the laser irradiated surface after polishing is 15% higher than that from the surface of the as-received sample.