Chiang Mai Journal of Science

This paper presents the results of the influence of laser alloying on structure and properties of the surface of HS6-5-2 high speed steel, carried out using a high power diode laser (HPDL). Niobium carbide powder was used for alloying. It was found out that remelting and laser alloying with carbide result in structure refinement across the entire investigated laser power range. Fine grained, dendritic structures occur in the remelted and alloyed zones with the crystallization direction related to the dynamical heat movement from the laser beam influence zone. The remelted zone structure is characterized by significant martensite dispersion with its laths several times shorter than those developed during conventional quenching. The fine grained martensite structure is responsible for hardness increase of the alloyed layer. Micro-hardness changes depend upon the effects of the laser beam on the treated surface, and especially in the alloyed layer. The outcome of the research provides better understanding of the structural mechanisms accompanying laser remelting and alloying. It has important significance and provides a basis for the practical employment of these technologies for forming the surfaces of new tools and regeneration of the used ones.