Friction and Wear Behaviors of Plasma Sprayed Conventional and Nanostructured WC-12Co Coatings at Elevated Temperature

Abstract

The conventional and nanostructured WC-12Co coatings were deposited by atmospheric plasma spraying with microstructured and nanostructured WC-12Co feedstock powders on 1Cr18Ni9Ti stainless steel substrate. Then, the friction and wear behaviors of the two types of coatings against silicon nitride ceramic ball were investigated with a sliding, reciprocating and vibrating SRV tester from 25 °C to 500°C under dry-friction condition. The microstructure, phase composition, microhardness, wear volume, worn surface morphology and wear debris of both coatings were characterized by combination of field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD), microhardness tester, 3D non-contact surface mapping profiler, and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The results showed that as-sprayed nanostructured WC-12Co coating possessed denser and finer structure, higher microhardness and less surface roughness than its conventional counterpart, although the slightly higher decomposition of WC in the former than that in the latter. In friction and wear test, the friction coefficients for both coatings took on minor difference including two varied regimes (25 °C∼200 °C and 300 °C∼500 °C) and the nanostructured coating exhibited slightly smaller friction coefficient than the conventional coating at the same test conditions. Moreover, compared with conventional WC-12Co coating, the plasma sprayed nanostructured coating showed better wear-resistance property at elevated temperature. The wear mechanism of nanostructured WC-12Co coating was delamination and adhesion wear, the latter was dominant wear mechanism at high temperature. While in the case of the as-sprayed conventional coating, it was a combination of brittle micro-fracture, fatigue wear and abrasive wear. Their wear behaviors were explained in terms of their microstructure, mechanical properties as well as wear debris obtained at elevated temperature.