Preparation Of Ti(C,N) Based Cermet And The Study On Microstructure And Property Of Ti(C,N) Based Cermet/45 Steel Brazed Joints

Ti（C,N）-based cermets have excellent mechanical properties and have been successfully applied to cutting tools,dies,special components and wear resistant tools.However,Ti（C,N）-based cermets is brittle,which makes it difficult to fabricate complex-shaped components.It is meaningful to realize the reliable bonding between Ti（C,N）cermet and metal.Because of the simple process,high joint strength,brazing is the most suitable to bond Ti（C,N）cermet and steel.In this paper,cermet and 45 steel has been successfully bonded by vacuum brazing.Meanwhile,scanning electron microscopy,X ray energy spectrum analyzer,X ray diffraction（XRD）,shear strength tester and micro hardness tester were used to analyze the microstructure,element distribution,interface products and strength of joints under different solder systems.Based on previous studies,three different ceramic components were designed.Ti（C,N）-based cermets were prepared by mould pressing and vacuum sintering,and the bending strength can up to 1900-2010MPa and the hardness up to 88-90HRA.The best performance group was selected as the base material for vacuum brazing.The cermet and steel were successfully brazed by the Ag-Cu-Ti filler.The brazing joint showed an intimate contact between the subtrates,There are no microcracks or pores in the joint and a distinct diffusion reaction layer was formed at the both interface.There are three distinct regions formed in the joint:the ceramic side reaction layer（I）,the metal side reaction layer（II）and the brzaing area（III）.The phase element composition was determined by EDS,The reaction layer I is mainly Cu-Ti intermetallic compound and TiNi₃.The reaction layer II is mainly composed of white Ag（s,s）and grey Cu（s,s）,and Cu-Ti compounds in it.Layer III is mainly FeTi and Fe₂Ti intermetallic compound.The shear strength of the joint reaches a peak of 203MPa when brazed at 920°C for 20min.On this basis,the effect of Mo additiont was analyzed.Ti（C,N）-based cermet and45 steel was successfully connected by using the AgCuTi+xMo（x=4 wt%;8wt%;12wt%;16 wt%）composite filler.With the increasing of Mo content in filler,the thickness of the reaction layer near the cermet decrease.Meanwhile,more blocky Ti-Cu intermetallic in the brazing seam were observed.With the Mo content increase,the shear strength of joint also increased.The maximum shear strength of 263 MPa was achieved when brazed with Ag-Cu-Ti+8wt%Mo composite filler at 1193K for 20 min.When that more than 8wt.%,the shear strength of the joint begin to decrease.At the same time,the Mo particles are evenly distributed in the AgCuTi filler metal,which can improve the microhardness of the filler.The results showed that the addition of suitable amounts of Mo particles into the Ag-Cu-Ti filler metal can significantly improves the shear strength of the joint.The Ti（C,N）-based cermet and 45 steel were successfully brazed by the Ag-Cu-Ti+Mo/Cu/Ag-Cu multi-layered composite filler.The results show that there are four obvious regions in the joint:ceramic side reaction zone I,AgCuTi+Mo filler zone II;copper foil interlayer III and AgCu filler zone IV.The reaction product from the ceramic side to the metal side is followed by:Cu₃Ti₂+Ni₃Ti;Ag（s.s）+Cu（s.s）+Mo+CuTi;Cu;Ag（s.s）+Cu（s.s）.When the brazing temperature is 920℃and the holding time is 20min,the shear strength of the joint reaches the peak value of 260MPa.The addition of Cu foil interlayer has no obvious effect on improving the strength of the joint.