Preparation and properties of Mo₂C-TiN_0.3 composite materials at high temperature and high pressure

Objectives: This study aims to prepare sintered bodies of Mo₂C and TiN_0.3 and explore their phase compositions, microstructures, and mechanical properties. Using a combined approach of mechanical alloying and high-temperature high-pressure sintering, the research investigates the stratified sintering process of Mo₂C and TiN_0.3 powders, analyzes the influence of different sintering temperatures on the sintered body performances, and aims to optimize the preparation process to enhance the comprehensive properties of the sintered bodies. Methods: This experiment employed a combination of mechanical alloying and high-temperature high-pressure sintering to prepare the sintered bodies. Initially, Mo₂C and TiN_0.3 powders were mechanically alloyed in a 7:3 volume ratio. The powders were thoroughly mixed using a high-energy ball mill to ensure uniform mixing. Subsequently, the mixed powders were subjected to high-temperature and high-pressure sintering using a six-sided top press under various temperature conditions to obtain sintered bodies with different sintering parameters. During the sintering process, the temperature and pressure were strictly controlled to study their effects on the microstructure and mechanical properties of the sintered bodies. The phase composition of the sintered bodies was analyzed using X-ray diffraction (XRD) to identify the presence and changes of various phases. The microstructure of the sintered bodies was observed using a scanning electron microscope (SEM) to analyze the grain size and morphology. To evaluate the mechanical properties of the sintered bodies, Vickers hardness tests and fracture toughness tests were conducted. These test methods were used to comprehensively analyze the overall performance of Mo₂C and TiN_0.3 sintered bodies under different sintering conditions. Results: The experimental results indicate significant mutual diffusion between Mo₂C and TiN_0.3 during the sintering process, forming two distinct diffusion layers. The formation of these diffusion layers markedly affects the phase composition and microstructure of the sintered body. As the sintering temperature increases, the grain size of the Mo₂C-TiN_0.3 sintered body gradually enlarges, leading to a deterioration in mechanical properties. Specifically, at lower sintering temperatures, the sintered body exhibits higher hardness, but as the temperature rises, the grain size increases, resulting in decreased hardness. Additionally, the formation of a highly hard and brittle MoC phase was detected during high-temperature sintering. In addition, MoC phase formation with high hardness and brittleness was detected during high temperature sintering. The presence of the MoC phase helps maintain the hardness of the sintered body within the range of 19.0 to 20.0 GPa, but also leads to a reduction in fracture toughness. The microstructure of the sintered body varies significantly with different sintering temperatures. Under low-temperature sintering conditions, the grains of the sintered body are small and evenly distributed, and the phase composition is relatively stable. However, with the increase of sintering temperature, the grains gradually grow, and the phase distribution becomes uneven, which leads to a decline in the mechanical properties of the sintered body. Furthermore, SEM analysis reveals the presence of numerous pores and cracks on the surface of the high-temperature sintered body, which are crucial factors affecting its mechanical performance. Conclusions: Through the study of 30% Mo₂C-TiN_0.3 sintered bodies, it is found that: (1) The mutual diffusion between Mo₂C and TiN_0.3 plays a crucial role in the formation of the sintered body, directly impacting its phase composition and microstructure. (2) As the sintering temperature increases, the grain size of the sintered body enlarges, leading to a decline in its mechanical properties, particularly in its hardness and fracture toughness. (3) The MoC phase generated in the sintering process helps to maintain the high hardness of the sintered body, but also reduces fracture toughness. Therefore, in practical applications, it is necessary to find a balance between hardness and toughness to optimize the overall performance of the sintered body. (4) Different sintering temperatures significantly affect the microstructure of the sintered body, highlighting the importance of optimizing sintering process parameters to enhance the performance of the sintered body. Others: The mechanical alloying and high-temperature and high-pressure sintering methods used in this study demonstrate the potential for producing high-performance Mo₂C and TiN_0.3 sintered bodies. By optimizing sintering process parameters, the performance of the sintered bodies can be further enhanced. Furthermore, future research could explore the effects of other additives on the performance of Mo₂C-TiN_0.3 sintered bodies to obtain higher performance hard and brittle materials.