Wear Resistance of HVOF-Sprayed Carbide Coatings

Abstract

Abstract The cermet materials have been developed to protect surfaces against wear and corrosion. In cutting tools technology as well as chromium replacement, WC coatings have been used to improve life and performance at higher temperatures. This work compares the abrasion and adhesion resistance of a WC-Co mixed in a x:y relation with a NiCrBSiW alloy deposited by High Velocity Oxy-Fuel (HVOF) process using a JP-5000 gun in two conditions: as sprayed and thermally treated. Abrasion and adhesion tests were performed according to ASTM G-65 and ASTM C-633 respectively. The microstructure and composition of the coatings, failure and worn surface were evaluated using Optical (OM) and Scanning Electron Microscopy (SEM) as well as X-Ray energy Dispersive Spectroscopy (EDX) and X-Ray diffraction (XRD). Vickers microhardness under a 500g load has been averaged from 8 indentations per sample. The results showed that the coatings studied presented a similar microhardness as well as good abrasion resistance. The best behavior of the post-heated coating could be attributed to a lower porosity, better distributions and effective cohesion between hard phases. Partial recrystallization of the amorphous phase produced during the thermal spray process into sub-carbides could be related to the improvement in abrasion resistance of the post-treated coating.