Room and high temperature wear behaviors of steelmaking slag coating and WC-reinforced composite coatings

Abstract

Steelmaking slag (SmS) powder and commercial WC-reinforced composite powders (NiCrBSi/WC (50/50) and WC/Co (88/12)) were deposited on the AISI 316 L stainless steel substrates by atmospheric plasma spraying (APS), and high velocity oxy fuel (HVOF) spraying techniques. The microstructures as well as the room and high temperature wear performances of the fabricated coatings were comparatively evaluated to assess the usability of steelmaking slag, an industrial by-product of steelmaking industry, as an alternative protective coating material against room and high temperature sliding wear. The friction-wear tests of all coatings against Al2O3 abrader were performed on a high-temperature ball-on-disk tribometer at room temperature and elevated temperatures (250 degrees C-500 degrees C) under 5 and 10 N normal loads. The powders, as-sprayed and worn samples were characterized by X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques and a 3D optical surface profiler. The SmS coating structure displayed the highest porosity which was followed by NiCrBSI-WC and WC-Co coatings. WC-Co coating exhibited the lowest specific wear rates until being damaged at 500 degrees C due to severe decarburization. NiCrBSi-WC and SmS coatings withstood the 500 degrees C wear test and NiCrBSi-WC coating slightly outperformed SmS coating under high load whereas SmS coating displayed lower wear rates under low load. SmS coating's stable oxide-rich structure acted in the favor of the coating's wear performance. The slight increase in the wear rate of SmS coating with the increase of temperature from 250 degrees C to 500 degrees C is believed to be induced by the large temperature gradients between the real contact areas and their surroundings. Overall, plasma sprayed SmS coating exhibited promising results when compared with its commercial HVOF sprayed WC-reinforced composite counterparts.