THE INFLUENCE OF LASER PROCESSING ON MICROSTRUCTURE AND SELECTED PROPERTIES OF THE DIFFUSION BORONIZED LAYERS PRODUCED ON TOOL STEEL FOR METAL FORMING

The paper presents the study results of microstructure, phase composition, microhardness and wear resistance of Vanadis-6 tool steel after diffusion boriding and laser processing. In this study the diode laser device was used. As a result of diffusion boriding the obtained surface layers were characterized by needlelike microstructure with good cohesion with the substrate but in the subsurface area delamination and porosity could be observed. Therefore the diffusion boronized layer was processed using laser heat treatment. As a result of influence of the laser beam, three zones were obtained. The remelted zone near the surface, next the heat affected zone and finally steel substrate were observed. The newly created microstructure in the remelted zone consisted of boron-martensite eutectic. Microhardness of boronized layer after laser processing in comparison to the one without laser processing was slightly lower and was approx. from 1300 HV0.1 to 1100 HV0.1. It was found that additional advantage of laser processing of boronized layers was the presence of heat affected zone. This led to obtaining a mild microhardness gradient between the surface and the substrate. The boronized layer after laser processing was characterized by higher wear resistance in comparison to one not subjected to this kind of processing.