| Ti?C,N?-Al2O3 ceramic matrix composite material has high hardness and wear resistance,as well as good resistance to oxidation and chemical stability.It is very promising as cutting tool material and high-temperature structural material.But the poor machining performance limits its application in industrial engineering.Based on these discussion,Ti?C,N?-Al2O3 and matel materials are always welded to enlarge its application scope.In this study,vaccum brazing and auxiliary pulse current diffusion bonding are used to connect Ti?C,N?-Al2O3 and 40 Cr steel.In this paper,Ti72Ni28 amorphous filler/Cu/Ag72Cu28 composite layer was used to connect Ti?C,N?-Al2O3 with 40 Crsteel by vaccum brazing.The results showed that The welding temperature and holding time have some influence on the microstructure and mechanical properties of the joints.The Ti in the solder can react with Al2O3 in Ti?C,N?-Al2O3 to generate Ti Oat 1000°C.The typical organizational structure of joints is:Ti?C,N?-Al2O3/Cu Ti2+Ti O+Ti2Ni/Ti?Cu,Ni?/Cu2Ti2Ni/Cu-based solid solution /Cu/40 Cr steel.The four point bending strength of joints increase with the increase of welding temperature,meanwhile,the four point bending strength of joints has parabolic relationship with holding time.The four-pointbending strength of joint at condition of 1000°C/30 min is largest,that is 158.4MPa.The reason of fracture failure is mainly due to the larger welding residual stress and the brittle compound layerin joint,the thermo physical properties of solder alloy and ceramic matrix composites are quite different,which caused through crackin ceramic matrix composites near weld zone when the holding time is too long.The Cu73Ti27 and Cu53Zr47 middle layer were employed to realize the auxiliary pulse current diffusion joints of Ti?C,N?-Al2O3 and 40 Cr steel.The diffusion behavior of elements and the interface reaction were studied and the effects of different processing parameters on the microstructure and mechanical properties of the joints were analyzed as well.The results showed that the activity element Zr has good wetting reaction performance to Ti?C,N?-Al2O3 ceramic matrix composites,Zr diffusesinto Ti?C,N?-Al2O3 ceramic matrix composites and substitution reaction between Zr and Al2O3 there.Then the activity of Al atoms are stimulated,enhance the diffusion capacity of the Al element,and generate the Zr O2 phase.Relationship between Welding temperature,holding time and joint four-point bending strength obeys the rule of parabola.The four-point bending strength of welding jointsusing Cu53Zr47 aregenerally higher than that of jointsusing Cu73Ti27.The largest four-point bending strength was achieved at900°C/6min using Cu53Zr47,which is418.0MPa.Cu/Ti and Cu/Zr diffusion couples were connected by auxiliary pulse current diffusion bonding under the condition of 700°C/10 min,interfacialcompact bonding and thick diffusion layer were acquired.Under the same welding process parameters,Cu/Zr side diffusion transition layer is thicker than that of Cu/Ti side.Heat preservation time produces great impaction on interface behavior of Ti/Cu/Zrdiffusion couple: when heat preservation time is short,the element diffusion is inadequateand interface reaction degree is low,so the metallurgical combination of interface is not dense enough,the diffusion layer is narrow,too,when extending heat preservation time,elements have enough time to diffuse adequately and participate in the interface reaction,which lead to the thickness of diffusion layer increases.Relatively,Cu/Ti diffusion couple is more sensitive to the change of holding time. |
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