Study On Interfacial Reaction Of Ti(C,N)/interfiller/40Cr By Auxiliary Electrical Impulses At Low Temperature And Diffusion Bonding

Ti（C,N）-based cermets is a kind of high performance tool materials, due to its wideperspective in application, the research of Ti（C,N）-based cermets/metals welding is veryimportant. In this paper, diffusion bonding of Ti（C,N）-based cermets with40Cr steel wasinvestigated, which include liquid-solid diffusion bonding, TLP diffusion bonding and SPSdiffusion bonding. The relationship between microstructure and diffusion bondingparameter was studied by X-ray diffraction （XRD）, scanning electron microscope （SEM）,energy dispersive X-ray detector （EDS）.In the part of liquid-solid diffusion bonding of Ti（C,N）-based cermets and40Cr steelwith Ti/Cu interlayer, the interface forming process and effect of changes of holding timeand pressure on microstructure of joints welded was studied. The results show that reactionlayer is thicker along with the expansion of diffusion holding time in the beginning, andthen has nothing changes. The microstructure on the side of Ti（C,N）-based cermets ismainly Ti₂Cu, TiAl₂and （Cu,Ni）,（Fe,Ni） under the parameter of950℃,60min,6MPa, Cubased solid solution and little TiC are mainly on the side of40Cr,In the part of TLP diffusion bonding of Ti（C,N）-based cermets with Ti/Ni/Ti interlayer,the fracture on the side of Ti（C,N）-based cermets and effect of changes of holding time onmicrostructure of joints welded was studied. The results show that the microstructure ofjoints welded changes with the expansion of diffusion holding time. The microstructure ofdiffusion bonding joints in the interface region is Ti（C,N）/Ti₂Ni+TiNi+TiAl₂/TiNi₃/Ni; Theresult of fracture analysis is that the crack generates from interstice and hole in liquid phaseregion near the side of Ti（C,N）-based cermets and spread towards Ti（C,N）-based cermets;Large number of diffusion path between Ti（C,N）-based cermets and interlayer is formed byNi-Ti transient liquid phase, which creates favorable conditions for solid diffusion in thenext step.In the part of SPS diffusion bonding of Ti（C,N）-based and40Cr steel cermets withAg-Cu-Ti/Cu/Ag-Cu, The interface forming process and effect of changes of holding timeand temperature on microstructure of joints welded was studied. The results show that themorphology of Ag-Cu-Ti/Cu bonding interface transforms flat into concave and convexshape with the elevation of temperature. Original Ag-Cu eutectic pattern fades away as aresult of diffusion and dissolution of Ag element from Ag-Cu interlayer to Cu foil, withlengthen of diffusion holding time. Diffusion reaction layer forms gradually on40Cr steelinterface at the same time. There are four stages of the interface forming process of joints under SPS diffusion bonding, which are surface contact, interlayer fusion, diffusion reactionlayer formation and solid phase composition homogenization. The microstructure on theside of Ti（C,N）-based cermets is mainly Cu based solid solution, Ti₂Cu+TiCu,（Cu,Ni）, andCu based solid solution and （Fe,Ni） are mainly on the side of40Cr steel. Ag based solidsolution is mainly near Cu foil in the weld joint.