化学气相沉积ZrC涂层的缺陷形成机制及控制

Formation mechanism and control of defects for ZrC ceramic coatings by chemical vapor deposition

为减少化学气相沉积(CVD)ZrC涂层的缺陷,提高涂层的性能和使用寿命,深入分析化学气相沉积过程中ZrC涂层的缺陷特征和形成机制,主要利用扫描电镜对CVD-ZrC涂层的表面和断口进行观察。结果表明:ZrC涂层中存在的3类典型缺陷,即裂纹、片状脱落和"蠕虫状"凸起,裂纹是在涂层生长过程或冷却过程中受到热应力形成的。片状脱落发生在薄膜边缘应力集中的局部区域,慢速沉积可以有效消除网状缺陷和面缺陷,也可有效抑制贯穿裂纹甚至片状剥落的出现;"蠕虫状"凸起形成于反应器进气口易形成紊流场的位置,该凸起起到了类似韧性相增韧和压应力增韧的双重效果。

In order to reduce the defect and improve properties and service life of zirconium carbide（ZrC） coatings,the feature and forming mechanism of defect from chemical vapor deposition process were analyzed.ZrC coatings were prepared on carbon/carbon substrate using ZrCl4＋C3H6＋H2＋Ar system.The results show that three types of defects,such as cracks,exfoliation and ＂vermicular＂ bulges were studied by surface and fracture SEM images.The defects characteristics and formation mechanism of defects were analyzed.The cracks were induced by growth and thermal stress.The results show that exfoliation always take place at edges of samples where the stress concentrates.Slow deposition is favorable to the coating defects control,especially to the plane-defects.＂Vermicular＂ bulges take place at gas inlet where turbulent flow forms,which can improve the toughness of the coating.