HVOF coating of Inconel 625 onto stainless and carbon steel surfaces: corrosion and bond testing

High velocity oxyfuel (HVOF) coating is extensively used in power industry to improve the corrosion and wear resistance of metallic surfaces. In the present study, HVOF coating of Inconel 625 onto stainless steel and mild steel surfaces is considered. The static electrochemical tests are carried out for different durations. Tensile bonding strength of the coatings before and after the electrochemical tests is measured. Optical microscopy and SEM are carried out to investigate the microstructure of the coating before and after the chemical tests. It is found that the coat has a noticeably layered structure with the layers parallel to the substrate’s surface and segregated by a slightly darker contrast phase presumed to be oxide. The tensile bonding strength of the coating reduces considerably after 3 weeks testing in the aqueous corrosion medium.