Improvement in tribological properties of HVOF sprayed WC–Co coatings using electroless Ni–P coated feedstock powders

The aim of this research is to investigate the sliding friction and wear behavior of a novel WC–Co thermal spray coating deposited from electroless Ni–P coated WC–12Co feedstock powders. The Ni–P coated powders were sprayed on ST37 steel substrate to form a coating, denoted as Ni–P modified WC–12Co coating, using high velocity oxygen fuel (HVOF) process. The X-ray diffractometry (XRD) and high resolution field emission scanning electron microscopy (HR FESEM) were used to analyze microstructural properties of Ni–P coated WC–12Co powders and the resultant coating. The sliding friction and wear behavior of Ni–P modified coating was investigated using a ball-on-disk technique under an applied load of 30 N. The Ni–P modified WC–12Co coating showed extremely lower decarburization level, higher hardness and fracture toughness as compared to the conventional WC–12Co and WC–17Co coatings. The wear rate of Ni–P modified coating was found to be ~ 3.2 × 10− 4 mg/m indicating ~ 68 and 72% improvement in wear resistance, with respect to the conventional WC–12Co and WC–17Co coatings. Moreover, the Ni–P modified coating exhibited the lowest average friction coefficient of ~ 0.4 with minor fluctuations. The dominating wear mechanism of Ni–P modified coating was individual WC particles pull-out following extrusion of Ni (Co) binder phase.