Evaluation of Hot Corrosion Behavior of WC-Co-Cr Coatings Coated by the HVOF Method

Abstract

Thermal spray coating techniques have wide-ranging applications in various fields, including marine, automotive, biomedical, and aerospace industries. These methods are popularly used because materials coated with thermal spray coatings exhibit excellent resistance to oxidation, erosion, corrosion, and abrasive environments, particularly at high temperatures. The present study utilized the high-speed oxy-fuel (HVOF) technique, a state-of-the-art thermal spray coating method, to apply a hard cermet ceramic coating material consisting of WC-Co-Cr onto a 316L stainless steel substrate. Isothermal hot corrosion tests were also conducted at 750°C in the presence of 45% Na2SO4 and 55% V2O5 hot corrosion salts for 1, 3, and 5 hours. Advanced characterization techniques such as X-Ray Diffractometry (XRD), Energy Dispersive Spectrum (EDS), scanning electron microscopy (SEM), and elemental mapping analysis devices were used to characterize the samples coated with the HVOF technique before and after hot corrosion tests. The findings indicate that WC-Co-Cr hard coatings, which are known for their high resistance to abrasion, sustain severe damage at high temperatures. The coating was damaged after 5 hours in the hot corrosion tests performed in the presence of V2O5 and Na2SO4 molten salt at 750°C. In addition, due to the progressing corrosion process in the coating layer, spills and deterioration occurred. Due to the shedding of the coating layer, damage has occurred in the substrate material.