Development of Ni-TiC and Ni- (Ti,W)C composite powders for high velocity oxy-fuel (HVOF) coating and characterisation of coatings

The main objective of this research work was to develop Ni-TiC and Ni-(Ti,W)C composite powders for high velocity oxy-fuel (HVOF) coating and characterisation of the coatings. For this purpose, two kind of composite powders were produced by the self-propagation high temperature synthesis (SHS) method (Ni-TiC and Ni-(Ti,W)C composites). Subsequently composite powders were used as feedstock for HVOF coating. Also, as reference sample, similar coating was prepared using Ni and TiC powders mixture. Samples were characterised by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy and adhesion tests. According to results, Ni-TiC and Ni-(Ti,W)C composite powders were developed via the SHS method yield appropriate HVOF coatings with dense, homogeneous, rounded, fused carbide distribution as well as suitable adhesive strength and high crack resistance. With an initial powdermixture of Ni and TiC for HVOF coating, TiC oxidation and Ti2O3 formation occurred; the microstructure of the coating was heterogeneous and irregular morphology having sharp facets. This coating had a low density and low adhesive strength and low crack resistance.