Microstructural characteristics and wear behaviour of HVAF sprayed Ni-SiC composite coatings

High-velocity air fuel (HVAF)-sprayed SiC coatings have been investigated as a potential approach to address challenges associated with their successful application through thermal spraying, since SiC can potentially serve as a sustainable replacement for WC in tribological hard coatings. Ni-P capped SiC feedstock was processed to fabricate composite coatings using HVAF, which is a relatively recent versatile and cost-effective spray technique. Three coatings, Ni-SiC-1, Ni-SiC-2, and Ni-SiC-3 were sprayed using various parameters to investigate the relationship between the processing conditions, microstructure, and wear performance. The extent of SiC retained in each of the coatings, albeit fragmented, was determined to be ∼25 % for each of the three coatings compared to the 54 wt. % SiC presence in the feedstock. However, despite the similarity in the quantity of SiC retained in the respective coatings, two of the coatings (Ni-SiC-1 and Ni-SiC-2) showed mixed amorphous and crystalline phases, whereas the Ni-SiC-3 coating was fully crystalline. The microindentation hardness of the coatings in the as-sprayed and annealed forms was noted to be in the range of 800–850 HV0.1. The specific wear rates for the respective coatings in the as-sprayed and annealed forms were found to be promising but of the same order of magnitude, revealing no significant role of annealing on their tribological behaviour. The results establish that it is possible to process a suitably designed SiC feedstock using HVAF to realize a sustainable wear-resistant coating.