THE INFLUENCE OF LASER TREATMENT OF POWDER STEEL PA-ZHGR ON THE GEOMETRIC PARAMETERS OF THE LASER EXPOSURE ZONE
The object of the study is the powder steel PA-ZhGr after laser surface treatment. The aim of the study is to study the effect of laser treatment on powder steel, identifying the dependence of the geometry and microhardness of the heat-affected zone on the processing parameters and the porosity of the material being processed. The results of studies of the microstructure and microhardness of the surface layer of the powder steel PA-ZhGr with a porosity of 4, 8, 10 % compared with cast steel U10 after laser treatment are presented. Samples of porous steel were obtained by traditional methods of powder metallurgy (mixture blending, pressing, sintering) with repeated pressing and annealing to obtain a given porosity. The laser treatment was carried out with a 1 kW fiber laser in argon with different spot moving speeds and streams of different power in the form of single tracks. Microhardness was measured at the cut of the sample at the center of the laser irradiation zone. The microstructure and geometrical dimensions of the heat-affected zone are obtained using an optical microscope. The microstructure of the treated zone of the cast and porous samples is shown. It was found that the microhardness of the treated surface does not depend on the porosity of the steel and has similar values on the surface of the treated zone for all samples. The percentage of porosity has an effect on the microhardness of the deeper layers, increasing the depth of hardening with decreasing porosity. Porosity also affects the geometry of the zone of influence, increasing the depth of the heat-affected zone with increasing porosity. The parameters of laser treatment of the surface of porous steels have been established, which contribute to the increase in microhardness and do not lead to the formation of cracks.