Grain growth and hardness of TiC-based cermets: Experimental investigation and thermodynamic calculations

摘要

In the present work, the influence of Mo and W additions and sintering time on the microstructure, grain growth and hardness of TiC-based cermets was systematically investigated by means of experimental determination and thermodynamic calculations. Under the guidance of the calculated carbon window, the TiC-based cermets with different Mo and W contents have been designed and sintered at 1430 degrees C in Ar atmosphere for 0 h, 1 h, 2 h and 5 h. The microstructure of cermets was observed by using scanning electron microscopy (SEM), while the volume fraction and average grain size of ceramic phase were measured by using ImageJ software. The volume fraction of ceramic phase decreases with the addition of Mo and W, which indicates the promoting effect of Mo and W on the carbide dissolution. The grain growth kinetics followed the cubic law, which was controlled by the diffusion of dissolved atoms through liquid binder phase (i.e. Ostwald ripening mechanism). The addition of Mo and W in TiC-based cermets can lead to a slow grain growth process during liquid-phase sintering. In addition, the Vicker hardness measurement was performed for the cermets, and the hardness was influenced by several factors, such as volume fraction and composition of binder phase, average grain size of ceramic phase and bonding strength of interface.