Modification of the steel surface layer for its better wear resistance by means of laser melting and alloying

摘要

The paper presents two different techniques: laser melting and laser alloying that use laser beam in order to change the surface layer properties. The microstructure and selected properties (microhardness, wear resistance and chemical composition) of the laser melted ASP 2060 high speed tool steel surface layer, as well as carbon steel laser alloyed with chromium, were investigated. The surface alloyed zones varied in microstructure, its depth, width and Cr content which depends on the thickness of pre-coated powder layer, binder type in the powder slurry and the process parameters (power and scanning velocity). The electron microprobe analysis of the alloyed layer showed that higher chromium content in the melted zone resulted from the thicker Cr pre-coating as well as slower scanning velocity. Scanning electron microscopy examinations show that dendritic structure of the melted zone becomes evident when an organic binder was used as one of the slurry components. It was also found that lower weight loss is obtained for higher chromium coating thickness as well as higher laser power.