Hardness of the Powder Coating PG-CP4 Applied to Steel 40H13 and Subjected Laser Treatment

Abstract

The article examines the hardness of the coating made of PG-CP4 powder. Plasma powder deposition was performed to samples made of 40H13 steel and then the samples treated with a laser beam. A multi-factor model was established that relates the hardness of the protective coating to the radiation power W, the longitudinal feed Spr of the laser beam, and the distance L from the protective casing of the laser head to the treated surface. Depending on the laser treatment modes, coating was in a state of complete, partial reflow or its absence. Full reflow is characterized by the adhesion of the filler material to the substrate, by maximum hardness of HRC 51.2–56.6 and no defects. In the absence of reflow, gas sinks, transverse microcracks, detachments, and other defects were found in the coating material, and the hardness decreased to HB 125–212. An increase in W and a decrease in Spr lead to increases the hardness of the treated coating, which is explained by an increase in the specific heat flux supplied to the coating per unit time, and a high rate of heat removal deep into the surface layer of 40H13 steel. The thickness of the surface layer with increased hardness ranged from 0.1 to 1.5 mm. Based on the multi-factor model, laser processing modes are controlled to ensure the required values of the protective coating hardness. The research results are recommended for use in enterprises that implement laser technologies and develop modern laser systems.