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在硅酸盐体系电解液中于铝合金表面制备出不同厚度的微弧氧化涂层,研究涂层厚度对基体疲劳寿命的影响,并揭示疲劳损伤机制。采用XRD、SEM、EDS等分析手段分析涂层的物相与组织结构。用810Material Test System疲劳试验机评价涂层试样的疲劳寿命。结果表明,铝合金微弧氧化涂层主要由γ-Al2O3和α-Al2O3组成,涂层内层致密,表面多微孔。随氧化时间延长,涂层厚度增大,但表面粗糙度增加。疲劳测试结果表明,微弧氧化涂层会降低基底铝合金的疲劳寿命,涂层厚度增加,疲劳寿命下降显著。相对于基体铝合金,涂层厚度为10,18,30μm的试样,疲劳寿命分别下降了4.4%,8.5%,32.2%。疲劳断口分析认为,涂层局部过度长入基体产生缺陷部位,在循环载荷作用下,容易产生应力集中,从而萌生疲劳源,使铝合金的疲劳寿命下降。
The micro-arc oxidation coating with different thickness was prepared on the surface of aluminum alloy in the electrolyte of silicate system to study the influence of coating thickness on the fatigue life of matrix and reveal the mechanism of fatigue damage. The phase and structure of the coatings were analyzed by XRD, SEM and EDS. The fatigue life of the coated specimens was evaluated using a 810Material Test System fatigue tester. The results show that the micro-arc oxidation coating of aluminum alloy is mainly composed of γ-Al2O3 and α-Al2O3, the inner layer of the coating is dense and the surface is microporous. With the prolongation of oxidation time, the thickness of coating increased, but the surface roughness increased. Fatigue test results show that the micro-arc oxidation coating will reduce the fatigue life of the base aluminum alloy, the coating thickness increases, the fatigue life decreased significantly. Compared with the base aluminum alloy, the fatigue life decreased by 4.4%, 8.5% and 32.2% respectively when the coating thickness was 10, 18 and 30μm. Fatigue fracture analysis shows that the coating locally grows too long into the substrate to produce defects, under the cyclic loading, stress concentration is easy to occur, thus initiating the fatigue source and reducing the fatigue life of the aluminum alloy.