Cavitation resistance of tungsten carbide applied on AISI 1020 steel by HVOF and remelted with CO2 laser

In engineering, there are major concerns about cavitation wear, as well as erosion, caused by the transport of abrasive sediments in hydraulic installations, like pumps and turbines, due to the damage these phenomena can cause in pumping stations and hydroelectric plants. Several studies are proposed to reduce this problem, like component design alteration and deposition of coatings with different materials that can be optimized for different wear issues. The objective of this work was to characterize and analyze the cavitation erosion of AISI 1020 steel samples coated with WC10Co4Cr deposited by high-velocity oxy fuel (HVOF) and laser-remelted with CO2 laser beam to evaluate the influence of this process in the cavitation erosion resistance of the coating. Microstructure, before and after laser treatment, was analyzed by means of optical and scanning electronical microscopy with SEM/EDS, indicated the metallurgical bonding between substrate and coating and a thickness reduction in the initial coating sprayed by HVOF of 100-35 mu m after laser irradiation, with an enhanced coating hardness (20%) near the surface. The cavitation erosion resistance evaluated using vibratory ultrasonic equipment, according ASTM G32-92 standard, indicated a reduction of 40% after laser treatment. This performance could be attributed to the surface densification of the HVOF-sprayed coating.