Formation of wear-resistant graded surfaces on titanium carbonitride-based cermets by microwave assisted nitriding sintering

•A new method for direct nitriding sintering functional graded cermet is proposed.•The influence of temperature on the formation of graded surface is investigated.•The new method showed greater nitride efficiency than the traditional sintering.

Microwave assisted nitriding sintering was used to form a wear-resistant graded surface on titanium carbonitride (Ti(C, N))-based cermets. The influence of processing parameters on the formation of wear-resistant graded surface layers on cermets was investigated. The nitriding process was carried out at liquid phase sintering temperature and with a maximum nitrogen pressure of 0.08 MPa. The formation of the wear-resistant graded surface layers depended on the temperature. Nitriding at 1430 °C formed a graded structure in which a (Ti, W, Mo, Ta) (C, N) governed microstructure changed into a hard metallic bulk structure with microscopic non-uniformities present in the matrix. A graded structure with only a (Ti, W, Mo, Ta) (C, N) layer was formed when nitrided at 1500 °C and 1530 °C. The microwave assisted nitriding sintering yielded greater nitride efficiency than the traditional sintering. At applied constant nitrogen press, the nitriding rate of the surfaces of samples decreased with increasing temperature, however, that of the bulk of the sample had the opposite tendency.