Effect of Carbide Particle Size on the Microstructure, Mechanical properties, and Wear Behavior of HVOF-sprayed WC-17% Co Coatings

This study investigates the effect of carbide particle size on the microstructure, mechanical properties, and abrasive wear resistance of WC-17%Co HVOF-sprayed coatings. The characteristics of WC-1, WC-2, and WC-3 coatings with carbide sizes of 1 µm, 0.9 µm, and 0.5 µm, respectively, were also investigated. WC-1 coating experienced the maximum carbon loss of 42%, while WC-2 and WC-3 coatings underwent lower carbon losses of 30% and 29%, respectively. The XRD pattern revealed W2C/WC peak ratios of 15.58, 9.14, and 14.96% for WC-1, WC-2, and WC-3 coatings, respectively. The Vickers microhardness of WC-1, WC-2, and WC-3 coatings was measured as 1418 ± 61, 1306 ± 71, and 1203 ± 57 kgf/mm2, respectively. The WC-2 coating showed the maximum fracture toughness of 5.9 MPa.m1/2, after which WC-3 and WC-1 coatings were characterized by 5.6 and 5.4 MPa.m1/2, respectively. The wear rate of the coatings abraded by alumina 60 was 1.2-7.8 times higher than that of the coatings abraded by silica 70 almost over the whole range of applied loads (19.6-127.5 N). The WC-3 coating exhibited lower abrasive wear resistance against alumina 60 than WC-1 and WC-2 coatings. The worn surfaces produced by alumina 60 abrasive showed indications of grooving, pitting, and cutting of the coatings’ surfaces. For all coatings abraded by silica 70, removal of the matrix, micro-grooving, carbide particles fragmentation, and voids formation through carbide pullout were detected. For WC-3 coating, in contrast to WC-2 and WC-3, the indications of sub-surface cracking were identified when abraded by both alumina 60 and silica 70.

Keywords:

WC-Co , HVOF , Microstructure , Mechanical properties , abrasive wear