Research On Process And Properties Of Plasma Arc Welding Ni60A/WC-12Co

In order to improve the surface wear resistance,nickel-based self-fluxing alloys with 60%tungsten carbides were deposited on the 45 steel substrate via plasma transferred arc welding to obtain an excellent bonding between substrate and deposit.The effects of weld current,welding speed,powder feeding rate on the microstructure and properties of the surface deposit were investigated,which provides technical support for fabricating tri-cone rotary drill bit.The microstructure were characterized by optical microscope(OM),scanning electron microscope(SEM)with energy disperse spectroscopy(EDS)and X-ray diffraction(XRD);the mechanical and wear properties were investigated by micro-hardness tester and wear test.The orthogonal experiment was designed including three kind of welding parameters,namely welding current(80,100,120 A),welding speed(0.06,0.08,0.10 r/min)and powder feeding rate(18,22,26 g/min).An excellent bond interface was obtained,and the WC particles were distributed homogenously in the surface deposit.The effects of different welding parameters on the morphology and distribution of WC particles were investigated.The results show that the welding parameters determine the morphology and distribution of WC particles.There are several typical morphologies of WC particles,including fragmental,featheriness,needle-like,cluster and fish-bone-like shapes.With the increase of welding current,the WC particles began to dissolve and transfer from fragmental and cluster shapes to needle-like and fish-bone-like shapes.Apart from WC particles and ?-Ni solid solution,several intermetallics such as FeNi3,Ni2.9Cro.7Feo.36 and Cr23C6 also exist in the surface deposit.With the increase of welding current,more intermetallics(Fe6W6C,Co6W6C)were formed at the expense of WC particles.The effects of welding parameters on the properties of surface deposit were investigated.The results indicate that the dilution rate,hardness and wear resistance mainly depend on the welding current,whereas the molding efficiency mainly depends on the powder feeding rate.The increase of welding current enhances the dilution rate and deteriorates the hardness and wear resistance;the increase of the powder feeding rate in enhances the molding efficiency.The optimal hardness and wear resistance were achieved,when the welding current,powder feeding rate and welding speed was selected as 80A?26g/min?0.10r/min.