Mo-SiBCN metal-ceramic composites with enhanced and tunable thermophysical properties and thermal shock resistance

In this study, Mo-SiBCN metal-ceramic composites with or without sintering additives of MgO, Al2O3, and SiO2 were fabricated by hot-press sintering at 1800 degrees C/60 MPa/30 min to investigate their phase composition, microstructural evolution, mechanical properties, thermophysical properties and thermal shock resistance. With the increase in amorphous SiBCN, a competition of reaction products between Mo and SiBCN as Mo3Si -> Mo3Si + Mo5Si3 + MoSi2 -> Mo4.8Si3C0.6 + Mo5Si3 + MoSi2 -> Mo4.8Si3C0.6 were detected. Meanwhile, the bulk density, elastic modulus and bending strength of the Mo-SiBCN composites gradually decrease with increasing SiBCN content, but their hardness first increases and subsequently decreases, reaching the highest value of 14.46 +/- 0.43 GPa with 30 vol% SiBCN incorporation. Due to the oxide additives that promoted the sintering of composites, the bending strength and hardness of Mo-SiBCN composites with the additives increased 3-6 times. The residual bending strength of the Mo-SiBCN composites after thermal shock at 900 degrees C and 1600 degrees C decreased with increasing SiBCN content, while for the composites with 10-20 vol% SiBCN, the residual bending strength increased by 140-147%.

Automated summary

This study investigated the phase composition, microstructural evolution, mechanical properties, thermophysical properties, and thermal shock resistance of Mo-SiBCN metal-ceramic composites with different sintering additives. The competition of reaction products between Mo and SiBCN was detected, with the increase in SiBCN content leading to a decrease in bulk density, elastic modulus, and bending strength, but an increase and subsequent decrease in hardness. The addition of sintering additives significantly improved the bending strength and hardness of the composites. The residual bending strength after thermal shock varied with SiBCN content, showing both increases and decreases.