Cf/SiC 复合材料表面 HfO2涂层的制备及其抗热冲击性能研究

目的研究等离子喷涂条件下Cf/SiC复合材料表面HfO_2涂层的物相、显微组织及其抗热冲击性能。方法通过水热合成和喷雾造粒制备出HfO_2粉体,并利用等离子喷涂在Cf/SiC复合材料表面制备HfO_2涂层,研究涂层的物相、显微组织和抗热冲击性能。结果水热合成的纳米HfO_2为单斜相结构,颗粒的平均粒径为10~15nm;等离子喷涂制备的HfO_2涂层组织中存在微裂纹和孔隙,涂层为单斜相结构,且经1350℃热处理后涂层的相结构未发生改变。等离子喷涂的HfO_2涂层与Cf/SiC复合材料基体结合良好,未观察到涂层、基体间界面分离的现象。经1350℃、50周次的空冷热冲击试验后,涂层未发生破坏失效;在1350℃水冷热冲击条件下,热循环20次时涂层表面出现剥落,27次时脱落面积50%。结论通过等离子喷涂制备的HfO_2涂层与Cf/SiC复合材料基体结合良好,涂层能够抵御1350℃空冷、50周次热冲击,且未发生破坏失效,涂层的1350℃水冷热循环寿命达27次。

Preparation of HfO2 Coatings on Cf/SiC Matrix Composites and Study of Its Thermal Shock Resistance

Objective To study the phase constituent, microstructure and thermal shock resistance of plasma sprayed HfO2 coatings on Cf/SiC matrix composites.Methods HfO2 powders were fabricated via hydrothermal synthesis and spray-drying process. The HfO2 coatings were prepared on Cf/SiC matrix composites by plasma spraying. The phase constituent, microstruc-ture and thermal shock resistance of the coatings were studied.Results The hydrothermal synthesized HfO2 particle exhibited monoclinic structure, and its average grain size ranged from 15 nm to 20 nm. Microcracks and holes were observed in the mi- crostructure of plasma sprayed HfO2 coatings. And the phase constituent of the sprayed HfO2 coatings kept monoclinic structure at 1350℃. The sprayed HfO2 coatings exhibited an excellent bonding condition with the Cf/SiC substrate. No spallation was observed between the coatings and the substrate. Under condition of 1350℃ water cooling-heating impact, surface disbonding occurred in the HfO2 coatings after 20 thermal cycles, and more than 50% surface area of HfO2 coatings disbonded from the substrate after 27 thermal cycles.Conclusion The plasma sprayed HfO2 coatings exhibited an excellent bonding condition with the Cf/SiC substrate, and could resist 50 thermal cycles of 1350℃ air-cooling test without degradation and failure. In wa-ter-cooling test, the life of the coatings could reach 27 thermal cycles.