Liquid phase sintering-based diffusion bonding of Ti(C,N)-based cermet and steel

Abstract

Sound joint of Ti(C,N)-based cermets and steel is achieved by liquid phase sintering of cermet green compact and steel, in which external pressure and interlayer metals are not required. The bonding process, joint microstructure, and properties are investigated. Liquid phase sintering occurs and typical core/rim structure forms in the cermet during diffusion bonding at 1593 K. Full densification of the cermet can be achieved after bonding for 2 h, the relative density, porosity, and grain size do not vary remarkably with the dwelling time during bonding. Bonding zones are composed of an austenite phase-based layer in the cermet side and a martensite phase-based layer in the steel side. There exists a Ni-enriched layer in the vicinity of cermet/bonding zone interface, which forms due to the outward diffusion of N and inward diffusion of Ti on the surface of cermet. The bonding zone thickness follows a parabolic relationship with the dwelling time. The microhardness of the bonding zones increases from the Ni-enriched layer, austenite layer to the martensite zone. The maximum value of residual stress locates in the bonding zone adjacent to the cermet, and the maximum residual stress value decreases with the dwelling time from the simulation results. Due to the existence of the Ni-enriched ductile bonding layer, a reliable joint can be achieved.