尖端结构对PS-PVD YSZ涂层沉积的影响

Effect of the tip structure with external centre on columnar-like PS-PVD coatings

采用等离子喷涂-物理气相沉积(PS-PVD)技术在设计的尖端结构试样表面制备了YSZ涂层,研究了YSZ涂层在尖端不同区域的形貌、厚度、孔隙率和微区力学性能的差异.结果表明:尖端部位各区域涂层呈现羽柱状结构,在涂层生长过程中柱状晶之间会因生长的空间受限而存在“挤压”竞争效应,尖端边角的几何特性会削弱“挤压”竞争效应,因此其涂层厚度远高于尖端其他区域;此外,尖端尖角附近的涂层羽柱状结构呈放射状,并沿基体表面法线方向向上生长;纳米压痕表明涂层硬度由顶部至底部呈现逐渐下降趋势,这与涂层结构和残余应力相关;尖端结构的尖角区域涂层微区硬度,显著高于尖端两侧区域;结合数值模拟分析结果发现,半封闭型面会导致等离子射流紊乱度上升,由于不同方向等离子体存在“卷流”和“冲击”现象,其对应沉积的涂层厚度下降,孔隙率上升.

The plasma spray-physical vapor deposition(PS-PVD)method is applied to prepare YSZ coatings deposited on the external surface centre.The morphology,thickness,porosity and mechanical properties of micro-zones are studied.The results show that all the coatings deposited on the sample are columnar-like structure.There are existed squeezing competition effects during the process of coatings growth due to the limited growth space.When the substrate was set as the external surface centre,the squeezing effect weakened due to the geometrical features.Therefore,the coating thickness at the corner is much higher than that at both sides.Besides,the overall structure of the coating presents radial diffusion.In addition,the results of nano-indentation show that the hardness of the coating is different in axial direction.It is the tensile stress that decreases the top-down hardness of the coating.The hardness of the coating deposited on the sharp cusp is higher than the sides.The simulation results indicate that the semi-closed profile can increase the turbulence of plasma jet.Due to the phenomenon of“turbulence”and“impact”of plasma in different directions,the thickness of the deposited coating decreases and the porosity increases.