Preparation and Performance of Electroless Nickel on HVOF (High-Velocity Oxygen Fuel) Sprayed Inconel 625 Nickel Coating for Corrosion Protection Applications

Abstract

High Velocity Oxy-Fuel (HVOF) spraying is one of the preferred surface engineering technologies that can offer advantages such as user-friendliness and cost-efficiency in mass production of coatings for various applications. While the main applications of the HVOF process are related to wear, corrosion resistance can be one of the important desired features of the surface engineering process. However, the porosity of HVOF sprayed coatings is usually a problem when coatings are used in corrosion applications. Low carbon steel substrates were High-Velocity Oxygen Fuel (HVOF) sprayed with Inconel 625 and then coated with a thin film of electroless nickel (electroless nickel plating). Reference sample without electroless nickel was sprayed at the same time. Characterization of the coatings was made by X-Ray diffraction analyses, microstructural surveys, cross-section and corrosion tests. Results showed that sequential application of HVOF spraying and electroless coating processes provided the multi-layered coating consisting of an inner inconel 625 based layer and an outer Ni-P layer. Electroless Ni-P also caused the remarkable increasing in the corrossion resistance as compared to the as-HVOF sprayed state.