DCP法W/ZrC金属陶瓷组成结构的高温演变研究

Study of microstructure evolution of DCP-derived W/ZrC cermets in ultra-high temperature

摘要:

采用置换填充工艺制备了W/ZrC金属陶瓷，研究了其在不同超高温温度环境中的组成结构演变规律。结果表明：随着热处理温度的升高，材料的质量损失率先增大后减小，在2200 ℃时有最大值2.05 wt.%，而孔隙率则不断增大，在2600 ℃时达到9.29 vol.%。在材料表面，残留Cu最先熔化挥发流失，其次残留Zr，在2600 ℃时部分ZrC也分解流失。在材料内部，1800 ℃时未反应完的WC相消失，2200 ℃时残留Zr-Cu合金相和W2C相消失，2600 ℃时仅剩下W相和ZrC相，且随着热处理温度的升高，W原子向ZrC基体中的扩散增多，导致ZrC点阵常数逐渐减小，W相由颗粒状变为无规则的长条状，其颗粒数量和体积含量明显减少，并形成了大量闭孔。Zr-Cu合金的流失和W原子的扩散是引起W/ZrC金属陶瓷在超高温环境中组织结构变化的重要原因。

Abstract:

W/ZrC cermets were fabricated by DCP method. The evolution laws of composition and microstructure of W/ZrC cermets in different ultra high temperature environment were investigated. Results show that the heat-treated microstructure of W/ZrC cermets is still comprised of metal tungsten and ceramic zirconium carbide. With an accretion of temperature, the weight loss first increases and then decreases, attaining a maximum 2.05 wt.% at 2200 ℃, and the open porosity increases constantly, reaching to 9.29 vol.% at 2600 ℃. On the materials surface, the residual Cu melt and volatilize firstly, and then residual Zr, a few ZrC vaporizing at 2600 ℃. While inside the materials, the WC phases disappear after heat treatment at 1800 ℃, also the residual Zr-Cu alloy phases and W2C phases at 2200 ℃, when heat treated at 2600 ℃, only W phases and ZrC phases reserve in W/ZrC cermets. Moreover, more W atoms diffuse into the ZrC phases along with the temperature increases, leading to lattice constants of ZrC decrease, and the orbicular W phases change to be ruleless long strip, also the quantity and volume fraction of W phases reduce, and lots of obturators form contrarily. The melting loss of remanent Zr-Cu alloy and diffusion of W atoms are important reasons for arosing composition and mircrostructure changes of W/ZrC cermets in ultra-high temperature.