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.