材料期刊网

在1450 ℃真空下保温1.5 h进行热压反应烧结制备了纯度为90%以上的Ti₃AlC₂和Ti₃SiC₂层状结构陶瓷, 研究了它们的物相组成、微观结构、力学性能及热物理特性, 并在2种陶瓷基体上进行了无金属粘结过渡层等离子喷涂ZrO₂ 热障涂层处理, 考察了涂层的结合强度与热冲击特性. 结果表明, Ti₃AlC₂和Ti₃SiC₂基体材料的抗弯强度和断裂韧性分别为536 MPa, 7.8 MPa·m^1/2和457 MPa, 6.8 MPa·m^1/2, 在25-1000 ℃温度范围内的平均线膨胀系数分别为8.77×10^-6和9.14×10^-6/℃, 前者的力学性能与热稳定性均优于后者; 等离子喷涂后, 整体材料的热导率下降幅度达60%以上, 涂层与基体结合牢固且具有良好的抗热冲击特性; 对2种基体的涂层隔热效应的计算表明, 0.3 mm厚ZrO₂涂层外表面与内界面的温差分别为341和358 ℃, 可显著提高工件的使用温度.

There has been a great interest in the synthesis and characterization of Ti₃AlC₂ and Ti₃SiC₂ lamellar ceramics due to their striking combination of merits of both metals and ceramics, such as good high-temperature strength, excellent oxidation resistance. In this study, dense and high purity polycrystalline Ti₃AlC₂ and Ti₃SiC₂ lamellar ceramics were prepared from Ti, Al(Si) and C powders by reactive hot pressing in vacuum at 1450 ℃ for 1.5 h under 30 MPa. Their phase constitution, mechanical characterization and thermal properties were investigated. In addition, plasma-sprayed monolayer ZrO₂ thermal barrier coatings free of metallic transition layer were prepared on the two ceramic substrates. The purity of the Ti₃AlC₂ and Ti₃SiC₂ were 91.5% and 90.3%, and the main impurity was TiC. The flexural strength and fracture toughness were 536 MPa, 7.8 MPa·m^1/2 and 457 MPa, 6.8 MPa·m^1/2 for Ti₃AlC₂ and Ti₃SiC₂, respectively. They took a respective average value of 8.77×10^-6 and 9.14×10^-6/℃ for the coefficient of thermal expansion (CTE) without remarkable temperature dependence between 25 and 1000℃. Furthermore, the coatings contributed to a more than 60\% decrease in the high temperature thermal conductivity compared to the two matrices. In general, Ti₃AlC₂ and ZrO₂-coated Ti₃AlC₂ displayed superior comprehensive properties to Ti₃SiC₂ and ZrO₂-coated Ti₃SiC₂. The temperature differences between the outside surface and the coating/matrix interfaces created by the thermal barrier coating were calculated to be 341 and 358 ℃ for Ti₃AlC₂ and Ti₃SiC₂ substrate, respectively.