Cold spraying of WC-Co-Ni coatings using porous WC-17Co powders

Abstract

Cold spray has been successfully used to produce WC-Co coatings in recent years, showing great potential. However, due to the lack of sufficient Comatrix phase for plastic deformation, the fabrication of cold sprayed WC-Co coating naturally requires expensive propulsive gas or very high working parameters, significantly increasing the manufacturing difficulty and cost.This paper aims to use conventional highpressure cold spray to fabricate high-performance and cost-effective WC-Co-Ni coatings, and to clarify its formation mechanism.To achieve this objective, mechanically mixed porous WC-17Coand dense Ni powders were selected as the feedstock with differentWC mass fraction, F1 (41.5 wt.%), F2 (64.5 wt.%) and F3 (74.7 wt.%).Working parameters were set at a moderatelevel (nitrogen, 3.0MPa and 350°C)to controlthe experimentalcost. Experimental results showed that WC reinforcementshad no phase transformation and were completely retained in the WC-Co-Ni coatings. The highest WC mass fractionwas present in the F3 coating,reachingapproximately 75% (equivalent to the feedstock), quite close to the cold sprayed WC-25Co coating. Fracture of WC-Co particles during the depositionprocesswas found to be the reason for such high WC retainability, dominating the coating formation mechanism.