Erosion–Corrosion Resistance of Laser Surface Alloying of NbC Thermal Spray Coatings on AISI 304L Steel

NbC coatings were flame sprayed on AISI 304L substrates and further remelted using a 400-W power ytterbium-doped fiber laser (YLR-500-MM-AC-Y11), inserted into a chamber for argon atmosphere control. For the selection of the remelting parameters, isolated beads with remelting of the coatings were performed using three focal lengths and three remelting speeds. Using the selected laser parameters, layers were remelted with eight passes and 40% superposition. Erosion–corrosion tests were performed in a solution of NaCl in distilled water with SiO₂. Surfaces and cross sections of the coatings were characterized by optical and scanning electron microscopy with dispersive energy microanalysis and x-ray diffraction. Microhardness measurements were taken in the cross section of the coatings. Modified surfaces 800 μm dense without pores or other defects and interfaces with the substrate of excellent metallurgical bonding were obtained. It was found that the dilution of the coating with the substrate formed a gradient of chemical composition and mechanical properties. The erosive–corrosive wear resistance of the laser-remelted coatings was higher for the eroding impact angle of 90°. When the impact angle was 30°, the weight loss was higher and the ductile wear mechanism was conditioned by the formation of pitting on the modified surface.