无压烧结制备硼化钨陶瓷

Preparation of Tungsten Boride Ceramic by Pressureless Sintering

采用两步法制备硼化钨陶瓷,首先将硼粉与钨粉按一定比例混合,在高温下合成硼化钨粉体,再以此为原料采用冷压和高温烧结制备硼化钨陶瓷。研究硼钨比例对合成粉体物相组成的影响,以及烧结温度对硼化钨陶瓷微观结构及力学性能的影响。研究结果表明:硼钨摩尔比为2.5时,可以得到纯度较高的WB2粉体。随着烧结温度的升高,WB2陶瓷的显气孔率减小,相对密度增加,材料的抗弯强度与显微硬度明显增大,当烧结温度达到1800℃时,WB2陶瓷的开口孔隙率为5.2%,相对密度86.0%,抗弯强度72 MPa,显微硬度2088.5 MPa。WB2陶瓷的断裂行为也从沿晶断裂转变为穿晶断裂模式。

WB2 ceramic was prepared by a two-step sintering method. Firstly, WB2 powder was synthesized by solid phase reaction using the mixed boron and tungsten powder as raw materials at high temperature. Secondly, WB2 ceramic was prepared by pressureless sintering using the above synthesized powder. The effect of boron/tungsten molar ratio on the phase composition of synthesized product, and the effect of temperature on the microstructure and mechanical properties of WB2 ceramic were investigated. The results showed that phase-pure WB2 could be obtained with B/W molar ratio of 2.5. The apparent porosity decreased, the relative density increased and the mechanical properties were improved greatly with the increase of sintering temperature. When the sintering temperature was up to 1800℃, the porosity, relative density, flexural strength and Vickers micro-hardness of WB2 ceramic were 5.2%, 86.0%, 72 MPa and 2088.5 MPa, respectively. The main fracture model of WB2 ceramic was changed from intergranular fracture to transgranular fracture.