Effect of thermo-elastic residual stresses on erosive performance of cermets with core-rim structured ceramic grains

Titanium carbide-based and nickel bonded ceramic-metal composites (cermets) possess a desirable combination of strength and toughness. In the present study the effect of microstructural features on a stress state in the composites of core-rim structured carbide grains (TiC-Mo2C) bonded up with nickel-based alloys is analyzed. Performance of the TiC-NiMo materials with ceramic particles content of 60 wt.% has been studied in the conditions of erosive wear to evaluate a dependence of the erosion rate on a stress state. The stress state is found to be influenced by the radii of core and rim and their micromechanical properties. The main mechanisms of erosive wear are binder removal, grain debonding and pull-out. All mechanisms are shown to be determined by thermo-mechanical stresses in cermets. To analyze the stressed state, the model for stress calculations in constituent phases was developed. The model considers two-phase inclusions embedded in a matrix. Depending not only on the difference in material properties and geometry of the phases, but also on local heating induced in the process of erosive wear, the model provides the quantitative description of the stress state in cermets. Results of modeling allow predicting geometrical parameters of composite to prevent crack formation and obtain the cermets of high tribological performance.