热震对包覆ZrB2-SiC-La2O3/SiC涂层渗硅石墨力学性能的影响

采用涂刷法和包埋法在渗硅石墨基体表面制备了双层结构的ZrB₂-SiC-La₂O₃/SiC防护涂层,与表面无包覆涂层的渗硅石墨作对比,采用三点弯曲实验方法研究了热震对其力学性能的影响。结果表明,1500℃到室温之间循环热震10次后,表面无包覆涂层的样品单位面积氧化失重为52.1 mg/cm²,弯曲强度保持率仅为52.0%;而包覆涂层样品单位面积氧化增重为5.6 mg/cm²,弯曲强度保持率达78.5%,包覆ZrB2-SiC-La2O3/SiC涂层的样品热震后能保持良好的力学性能。在热震过程中ZrB₂-SiC-La₂O₃/SiC涂层氧化生成的氧化层可有效地保护石墨基体不被氧化,避免了样品内部各种缺陷的产生,从而提高了其弯曲强度。

Effect of Thermal Shock on Mechanical Properties of Siliconized Graphite with ZrB2-SiC-La2O3/SiC Coating

A ZrB₂-SiC-La₂O₃/SiC dual-layer coating was prepared on siliconized graphite by the combination of slurry method and pack cementation.The mechanical properties of the coated siliconized graphite before and after thermal shock were investigated and compared with the bare siliconized graphite.The mass loss was observed and its value of per unit area of the bare siliconized graphite was 52.1 mg/cm₂,and the flexural strength retention was only 52.0%after thermal shock test from 1500℃to room temperature for 10 cycles,while they were 5.6 mg/cm²and 78.5%for the coated ones,respectively.The high strength retention of the coated siliconized graphite after thermal shock could be attributed to the formation of a protective oxide scale on its surface,which protected the graphite substrate from oxidation and avoided the formation of defects in the interior regions of the coated siliconized graphite.