等离子喷涂Al_2O_3涂层的电击穿机理

Electrical Insulating Properties of Plasma Sprayed Al_2O_3 Coating

采用大气等离子喷涂技术在铜基体上沉积了Al2O3涂层。采用XRD和SEM对涂层微观结构进行了表征。通过探讨孔隙率和吸潮行为对绝缘性能的影响,分析了等离子喷涂Al2O3涂层结构与电绝缘失效机理的关系。结果表明：等离子喷涂Al2O3涂层较致密,界面结合较好。随涂层厚度不同其孔隙率在5%～7%范围变化。等离子喷涂Al2O3涂层结构中的孔洞是电绝缘失效的主要部位且呈典型电晕击穿形貌。电晕击穿诱发的裂纹沿击穿方向扩展形成击穿隧道。击穿方向与电极极性无关而由击穿孔洞位置决定。涂层厚度与涂层击穿强度呈现倒数关系。吸潮会诱发导电通路形成降低A12O3，涂层抗击穿能力。

Al2O3 insulation coating was deposited by atmospheric plasma spraying （APS） method on Cu substrate. The microstructures of the Al2O3 coating were characterized by XRD and SEM. Based on the investigation of the influences of porosity and moisture absorption behavior on insulation performances, the relationship between the structure of plasma spraying Al2O3 coating and property of electric insulation failure was analyzed. Results show that the as-sprayed Al2O3 coating has dense structure and good interface bonding between the Al2O3 coating and suhstrate, whose porosity changes in the range of 5% to 7% as coating thickness varies. The breakdown of as-sprayed coating always occurs at the position of the hole, which demonstrates a typical morphology of corona breakdown. The cracks resulted from corona breakdown prolongates along the direction of the breakdown are formed as a tunnel. The direction of break- down is closely related with the position of holes not the electrode polarity. There is a reciprocal function relation between coating thickness and breakdown strength of the coating. The formation of the conductive path caused by moisture absorption results in decrease of the insulate property of assprayed coating.