Microstructure, interface characteristics and mechanical properties of Ti(C,N)-based cermets with a cellular structure

Abstract

A novel method was proposed to prepare Ti(C,N)-based cermets with a cellular structure by controlling the drying conditions and subsequent vacuum sintering, the as-prepared cermets combine the advantages of fine grains with those of coarse grains, and show superior mechanical properties compared to conventional cermets. The microstructure, interface characteristics and mechanical properties of cellular cermets were systematically investigated. The SEM analysis revealed that cellular cermets comprised fine-grained aggregates and coarse-grained matrix; these aggregates were distributed in the matrix, which formed obvious interfaces between them. With increasing drying temperature and decreasing drying gas pressure, the volume fraction of aggregates in vacuum-sintered cermets first increased and then decreased. In addition, semi-coherent and coherent relationships were formed at the ceramic/binder phase boundaries in the aggregates and matrix, respectively, leading to the improvement of toughness. By optimizing the drying conditions, significant grain refinement was observed in the cellular cermets; these cermets exhibited excellent mechanical properties, i.e., hardness of 93.2 ± 0.1 HRA, transverse rupture strength of 2030 ± 32 MPa, and fracture toughness of 8.8 ± 0.1 MPa m1/2. The refinement of ceramic grains was found to be the dominant factor responsible for the increased hardness and strength, while the improvement of toughness was mainly due to the unique characteristics of the aggregates and matrix.