Investigation On Microstructure And Properties Of Dual-scale WC-12Co Coating Deposited By HVOF

According to this research, dual-scale WC-12Co mental ceramic coating wasdeposited by High Velocity Oxy-Fuel(HVOF) technique.the properities of the coatingwas investigated by means of Metallographic(OM), Scanning Electron Microscopy(SEM), X-ray Diffraction (XRD), Micro hardness Tester and Wear resistanceexperiments.A dense and homogeneous coating of dual-scale WC-12Co was deposited byHVOF, which was composed of deformed strip shaped particles binding with Co. Itwas found that the substrate and the coating were bonding well and mainlymechanical bonding. Based on index of coating hardness and porosity, influence ofthe change in propane and oxygen flow rate, powder structure，spray distance wasstudied.The porosity of dual-scale WC-12Co coating could be lower than1%. In theselected parameters, the micro hardness was as high as1000HV0.1. It was analyzed inthe distribution of micro hardness between coating and substrate and there was nosignificant difference in micro hardness between longitudinal and cross-section. Theporosity and micro hardness was inversely proportional. When the pressure and flowrate of C3H8were0.6MPa,22.5L/min, pressure and flow rate O2were0.6MPa,225L/min, spraying distance is300mm, the micro-hardness of dual scale WC-12Cocoating is1051HV0.1，micro-hardness of dual-scale WC-12Co coating was lowernano-coating but higher than micron-coating, combined strength was greater than67MPa; fracture toughness reached to11.3MPa*m1/2，it is the highest of the three kindof coating, The comprehensive mechanical properties of dual-scale WC-12Co coatingare the best of the three.HVOF coating of WC-12Co was mainly used as a wear-resistant coating. It wasimportant that the level of wear resistance and mechanisms.The coating had betterwear resistance. In the dry sliding condition, the wear loss of coating was less thanGCr15about78times by one hour and108times by2hours, under the samecondition friction coefficient of dual-scale WC-12Co coating is about0.61. Thefriction coefficient under the condition of lubrication is far lower than the coefficientof friction of the dry wear.The wear process was begin with cutting the soft metal Co,and lead to WC particles falling.Finally,the WC particles were as a hard abrasiveof the abrasive wear dominated. It was detected that Fe element in the surface ofcoating which was shift from another friction component.