Purpose: The aim of this paper was to study the laser treatment technique and parameters, particularly the laser power, to achieve a high value of layer properties like hardness and microhardness for protection of this hot work tool steel from losing their work stability and to make the tool surface more resistant for work. The purpose of this work was also to determine technological and technical conditions for remelting the surface layer with HPDL.Design/methodology/approach: This work presents the results of new laser treatment techniques applied in metal surface technology. There is presented laser treatment with remelting and/or alloying of X40CrMoV5-1 and 32CrMoV12-28 hot work tool steels with carbide powders as well as results of laser remelting influence on microstructure and properties of the surface, carried out using the high power diode laser (HPDL). Special attention was devoted to monitoring of the layer morphology of the investigated material and on the particle occurred.Findings: The layer is without cracks and defects as well as has a considerably higher hardness value compared to the non remelted material. The hardness value increases according to the laser power used so that the highest power applied gives to highest hardness value in the remelted layer.Research limitations/implications: The results present only four selected laser powers by one process speed rate. Also carbide powders were used for alloying with the particle size in a chosen range.Originality/value: The originality of this work is based on applying of High Power Diode Laser for improvement of steel mechanical properties.