Preparation and sintering properties of the coated SiO₂/Al composite powders

To overcome the difficulty in the uniform phase distribution, wetting interface, and sintering densification of the cermets, the reinforced phases were uniformly wrapped and distributed on the surface of the base materials by ball-milling technology to improve the comprehensive performance of the cermets. The ball milling parameters and sintering properties of the coated SiO₂/Al composite powders were investigated in this paper. The results show that, the specific surface area of the SiO₂/Al composite powders increases first and then decreases with the extension of the milling time, and the specific surface area of the SiO₂/Al composite powders shows the largest and reaches 8.1 m²·g⁻¹ by ball milling for 6 h. The specific surface area of the SiO₂/Al composite powders increases first and then decreases with the increase of the ball-to-material ratio, indicating that the SiO₂ content coated on the surface of Al powders increases first and then decreases. With the increase of milling speed, the specific surface area of the SiO₂/Al composite powders increases first and then decreases. With the increase of sintering temperature, the surface hardness of the SiO₂/Al cermets increases first and then decreases. When the sintering temperature is 900 ℃, the surface hardness of the SiO₂/Al cermets reaches the highest. The better properties of the SiO₂/Al cermets are obtained when the ball milling time is 6 h, the ball-to-materials ratio is 2:1, the ball milling speed is 360 r·min⁻¹, and the sintering temperature is 900 ℃.