Microstructure and properties of the Ti(C,N)-xMo2C-Ni cermet/steel joint by a novel diffusion bonding method

Ti(C,N)-based cermets and steel were joined by a novel diffusion bonding method, which was combined with the liquid phase sintering process of the cermets. The effect of Mo2C content of the cermets on the microstructure and properties of the joint was investigated. The results showed that there existed core/rim structure in the cermets and the rim phases became thicker with the increase of Mo2C addition. Ti and Ni diffused toward the steel side, and Fe diffused toward the cermet side during bonding. The joints were composed of three or four bonding zones, i.e. cermet surface layer (A), Fe-enriched cermet layer (B), austenite layers (C) and martensite layer (D). Without Mo2C addition, the joint consisted of bonding zones A, C and D with the largest residual stress value. 5 wt.% Mo2C addition resulted in the formation of zone B and increase of bonding zone thickness, thus the residual stress decreased. Further increase of Mo2C lead to the thickness decrease of bonding zones since the diffusion of Ti and Ni are inhibited, hence the residual stress increased obviously. The cermet of 5 wt.% Mo2C showed the highest shear strength due to the sound microstructure and lowest residual stress level.