氧化时间对微弧氧化非均质陶瓷膜工频击穿特性的影响

Effect of Oxidation Time on the Power Frequency Breakdown Characteristics of Micro-arc Oxidation Inhomogeneous Ceramic Film

目前对微弧氧化陶瓷膜绝缘击穿特性的研究多集中于改变工艺参数所产生的影响,对处于不同生长阶段的陶瓷膜绝缘击穿特性尚不清晰。为此,研究了陶瓷膜生长过程中工频击穿特性的变化规律及内在作用机理。首先,以氧化时间为变量制备陶瓷绝缘导线样品;其次,对陶瓷膜的表面与截面形貌、元素分布、物相组成等显微特征进行分析;进一步采用双参数Weibull分布法获得陶瓷膜工频击穿特性随着氧化时间的变化规律;最后,分析明确工频击穿特性的关键影响因素和内在机理。研究结果表明:陶瓷膜生长过程中工频击穿电压呈现出非线性上升趋势,根据上升速率可分为快慢交替的4个区间,分别是氧化时间为2~6 min、6~14 min、14~18 min和18~30 min,上升速率分别为17.91、8.43、25.38和8.60 V/min。陶瓷膜增厚和Al_(2)O_(3)物相转化是使工频击穿电压增加的主要原因。在陶瓷膜生长过程中,陶瓷膜厚度和粗糙度呈现近似线性增加趋势,增长率分别为2.32μm/min和0.15μm/min;陶瓷膜的致密度呈下降趋势,从1.46 g/cm^(3)降低至0.05 g/cm^(3)。当氧化时间为16 min时,陶瓷膜中出现α-Al_(2)O_(3)晶相,并且α-Al_(2)O_(3)的质量分数随着氧化时间的增长逐渐升高,最大为21.37%。因为工频击穿场强为平均数值并反映陶瓷膜的平均耐压强度;所以随着氧化时间的增加,工频击穿场强呈现负指数形式下降,从34.25 V/μm减小至7.33 V/μm。陶瓷膜微观结构和物质组成的非均质特性是影响其工频击穿特性变化的关键因素。

At present,the research on the insulation breakdown characteristics of micro-arc oxidation ceramic film is mostly focused on the impact of changing the process parameters.The insulation characteristics of ceramic film in differ-ent growth processes are not clear yet.Therefore,this paper investigates the change rule and internal mechanism of the power frequency breakdown characteristics of ceramic film growth process.Firstly,the ceramic insulation wire samples with different oxidation times were prepared.Secondly,the surface and cross-section morphology,elemental distribution,phase composition and other microscopic features of the ceramic film were analyzed.Further,the two-parameter Weibull distribution method was used to obtain the variation rule of the power frequency breakdown voltage of the ceramic film with the oxidation time.Finally,the key factors and internal mechanisms affecting the breakdown characteristics were an-alyzed.The results show that the power frequency breakdown voltage during the growth of ceramic film shows a nonlinear trend.The rising rate can be divided into four intervals with alternating fast and slow speeds,the oxidation time is determined to be 2~6 min,6~14 min,14~18 min,and 18~30 min intervals,and the rate of increase of the power fre-quency breakdown voltage is 17.91 V/min,8.43 V/min,25.38 V/min,and 8.60 V/min,respectively.The thickening of the ceramic film and the phase transition of Al_(2)O_(3)are the major factors for the increase of the power frequency breakdown voltage.During the growth process,the thickness and roughness show a linear increase trend,with the growth rate of 2.32μm/min and 0.15μm/min,respectively.The density of the ceramic film shows a decreasing trend from 1.46 g/cm^(3)to 0.05 g/cm^(3).When the oxidation time is 16 min,theα-Al_(2)O_(3)crystalline phase appears in the film and the mass fraction ofα-Al_(2)O_(3)is gradually increased with the growth of the oxidation time,and the maximum is 21.37%.Because the power frequency breakdown field strength is an average value and reflects the average strength of the ceramic film.With the increase of oxidation time,the power frequency breakdown field strength shows a decrease trend,from 34.25 V/μm to 7.33 V/μm.The inhomogeneous characteristics of the microstructure and material composition of the ceramic film are the key factors influencing the change of the power frequency breakdown characteristics.