Laser modification of surface layer properties of a hot-work tool steel

Purpose: The objective of the present work was to study the modification of the microstructure of hot-work tool steel X40CrMoV5-1 during the surface modifying by means of laser technology. Design/methodology/approach: The initial experiments consisting in alloying the hot work tool steel indicate to the clear influence of the laser power on the run face shape and its depth. Findings: The structure of material solidifying after laser remelting is characteristic of the diversified morphology connected with the repeated changes of the crystals’ growth direction, from the small dendrites, whose principal axes are oriented in accordance with the heat removal directions at the boundary between the solid and liquid phases, clusters of carbides arranged in accordance with the swirls caused by the metallic liquid convection motion, and partially non-remelted WC conglomerates as the alloying material in the central area of the remelted zone, to the fine equiaxial grains in the subsurface zone. Research limitations/implications: Laser remelting and alloying with the tungsten carbide results in refinement of the structure in the entire laser power range and in diversification of the grain size in the particular surface layer zones. Practical implications: Laser alloying has the important cognitive significance and gives grounds to the practical employment of these technologies for forming the surfaces of new tools and regeneration of the used ones. Originality/value: The fine grained, dendritic structure occurs in the remelted and alloyed zone with the crystallization direction connected with the dynamical heat abstraction from the laser beam influence zone. The fine grained martensite structure is responsible for hardness increase of the alloyed layer.