The influence of laser surface alloying on the thermal fatigue resistance of hot work tool steels

The paper presents results of the effect of laser surface remelting and alloying by carbides powders of NbC, TaC, TiC, VC and WC on the structure and thermal fatigue resistance of the surface layer of hot work tool steels X40CrMoV5-1 and 32CrMoV12-28. The laser surface alloying and remelting treatments was performed using a high power diode laser (HPDL ROFIN SINAR DL 020). In order to investigate the effect of applied laser treatments and used alloying powders on the microstructure and thermal fatigue resistance of processed surface layer of hot work tool steels, the microstructure evaluation by light microscopy, hardness test, and dedicated thermal fatigue resistance test were performed. The best results regarding fatigue cracks inhibition was obtained when the surface of hot work tool steels was alloyed with TiC and VC carbides at the laser beam power of 2.0 and 2.3 kW. The grain refinement effect of laser remelting has a lower impact on the thermal crack inhibition, than a strong strengthening effect of matrix saturation in alloying elements and precipitation of fine carbides in the steel matrix.