Microstructure evolution and densification behavior of cellular Ti(C,N)-based cermets prepared by multiphase flow agglomeration and subsequent vacuum sintering

Abstract

The cellular Ti(C,N)-based cermets were prepared by multiphase flow agglomeration and subsequent vacuum sintering. By precisely controlling the vacuum degree and temperature, the fine particles collided and then agglomerated together through the surface tension of bubbles generated by the dissolved gas in the slurry, forming a multiphase flow with the liquid medium as the slurry dried. Subsequently, the dried powder mixture containing the agglomerates was subjected to pressing and vacuum sintering to obtain cellular cermets. The cellular cermets were analyzed using DSC, XRD, SEM, TEM, and EDS. During the solid-phase sintering stage, the agglomerates were relatively loose and easily to be destroyed, showing large gaps with the matrix, while the gaps gradually decreased and the density slightly increased as the temperature increased. During liquid phase sintering, the grains in agglomerates were further dissolved to gain fully fine-grained agglomerates, and the interface between the agglomerates and the matrix became clear. Finally, a dense sintered body with cellular structure in which agglomerates were dispersed in the matrix was formed. Furthermore, agglomerates were mainly composed of grains with black core-gray rim and grains without obvious core/rim structure, forming distinct interfaces with the coarse-grained matrix. The cellular Ti(C,N)-based cermets exhibited superb mechanical properties, with TRS of 2184 ± 30 MPa, fracture toughness of 9.01 ± 0.3 MPa m1/2, and hardness of 93.4 ± 0.2 HRA, making them superior to traditional Ti(C,N)-based cermets.