Characterization of phase transformation and microstructure of nano
hard phase Ti(C,N)-based cermet by spark plasma sintering①
hard phase Ti(C,N)-based cermet by spark plasma sintering①
(1. State Key Laboratory of Die & Mould Technology,
Huazhong University of Science and Technoloty, Wuhan 430074, China;
2. Department of Mechanical & Materials Engineering,
China Three Gorges University, Yichang 443002, China)
Huazhong University of Science and Technoloty, Wuhan 430074, China;
2. Department of Mechanical & Materials Engineering,
China Three Gorges University, Yichang 443002, China)
Abstract: By means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), the process of densification, the characterization of phase transformation and the microstructure for spark plasma sintering (SPS) nano hard phase Ti(C,N)-based cermet were investigated. It is found that the spark plasma sintering (SPS) enables the nano hard phase Ti(C,N)-based cermet to densify rapidly, however, the full densification of the
sintered samples can not be obtained. The rate of phase transformation is significantly quick. When being sintered at 1200℃for 8 min, Mo2C is completely dissolved, and TiN dissolves into TiC entirely and disappears. Above 1 200℃, Ti (C,N) begins to decompose and the atoms of C and N separate from Ti(C,N) resulting in the generation of N2and the graphite. Due to the denitrification and the graphitization, the density and the hardness of sintered samples are rather
low. The distribution of grain size of the sample sintered at 1 350℃covers a wide range of 90 500 nm, and most of the grain size are about 200 nm. The hard phase is not of typical core-rim structure. Oxides on the surface of particles can not be fully removed and present in sample as titanium oxide TiO2. Graphite exists in band-like shape.
sintered samples can not be obtained. The rate of phase transformation is significantly quick. When being sintered at 1200℃for 8 min, Mo2C is completely dissolved, and TiN dissolves into TiC entirely and disappears. Above 1 200℃, Ti (C,N) begins to decompose and the atoms of C and N separate from Ti(C,N) resulting in the generation of N2and the graphite. Due to the denitrification and the graphitization, the density and the hardness of sintered samples are rather
low. The distribution of grain size of the sample sintered at 1 350℃covers a wide range of 90 500 nm, and most of the grain size are about 200 nm. The hard phase is not of typical core-rim structure. Oxides on the surface of particles can not be fully removed and present in sample as titanium oxide TiO2. Graphite exists in band-like shape.
Key words: Ti(C,N)-based cermet; nano phase; spark plasma sintering; phase transformation; microstructure