Study On Preparation Of Gradient Cemented Carbide And Its Arc Welding To Steel 45

WC-Co has been widely used in various fields of industry due to its excellent properties.However the cemented carbide with low binder phase can't arc cold welding to steel,because there is a difference in the coefficient of thermal expansion of the two materials.It had been proved that YG30 could connect with steel by arc cold welding.Therefore the development of gradient cemented carbide which exhibits both high hardness and excellent weld ability has important research significance.This paper selects YG8,YG15,YG20,WC-5Co-25 Ni hard alloy as the base material,The gradient cemented carbide was prepared by diffusion sintering,and then the TIG welding of the gradient cemented carbide and the 45 steel is carried out.The Microstructure,element diffusion and mechanical properties of welded joints were studied by scanning electron microscope(SEM),Energy Dispersive Spectrdmeter(EDS),X ray diffraction(XRD),Vickers hardness and bending strength test.The main conclusions were as follows: The WC powder with uniform texture and single phase could be obtained at high temperature in 2h,simultaneously the total carbon content was controlled at 10.8%.It can be made of cemented carbide without pores,cracks and surface deformation by sintered WC-25Ni-5Co at 1400 ?for about 90 minutes.In order to obtain the gradient cemented carbide with good interface,no cracks and smoothing surface from cemented carbide with different binder phase,Diffusion sintering process conditions are sintering temperature of 1400 ?,sintering time of 75 min,followed by slow cooling.The driving force of the binder phase depends on the grain size and osmotic pressure which caused by Solute concentration gradient in liquid phase.The welding joint of gradient cemented carbide and steel which is no macro defects are fabricated at 100 A continuous current under Argas protective environment.The research indicated that using Without warm up before welding and Air Cooling after welding technology could promote welding-joint quality.The welding groove anglewhichwas30 degrees needs to be set on the gradient cemented carbide.Therefore,the formation of H phase is suppressed effectively due to the rate of dilution of the base metal can be controlled.There is plastic deformation before bending of the welded specimen with good performance.When the specimen is fractured,it is brittle fracture.The results indicate that according to the above process,the welding of gradient cemented carbide and 45 steel is feasible.Simultaneously welding mechanical properties is stable and excellent.