涂层厚度对硬脆涂层结合强度的影响

Effect of the coating thickness on the bond strength for brittle coating-substrate system

应用有限元分析的方法分析二维模型涂层层数以及涂层厚度对涂层/基体结合强度的影响已得到广泛研究。然而二维模型相比三维模型未能考虑宽度方向应力应变的影响,导致求解精度低。因此对三维模型涂层层数以及厚度对涂层/基体结合强度影响的研究显得实为重要,但这方面研究比较少。本文建立有限元三维模型,通过比较有限元模拟结果与赫兹接触精确解析解验证了模型的可靠性,讨论了涂层厚度对涂层/基体界面最大剪切力影响关系。结果表明,剪应力最小值随着涂层厚度的增加逐渐减小,然而剪应力最大值却随着厚度的增加先减小后增大,在0.4mm时取得最小值;随着涂层厚度的增加,涂层/基体结合处剪应力Z方向突变减小,涂层内部剪应力Z方向突变增大,但是突变位置向涂层表面靠近,而且涂层/基体结合处X方向的剪应力变化随着涂层厚度增加趋于平缓。

With finite element method （FEM）,the relationships of the bond strength with the thickness and the number of the brittle coating has been widely studied in 2-D model. Compared to these in 3-D model, the stress and strain in the width direction are ignored in 2-D model. It is necessary to investigate the effect of the thickness and the number of the coating on the bond strength for the brittle coating/ substrate in 3-D model. A 3-D model was built and the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model. This paper discussed the relationship between the thickness of coating and the maximum shear stress of the coating/substrate. It was found： firstly,with the increase in the thickness, the minimum of shear stresses happened in coating/substrate decreased and the maximum of shear stresses happened at the top of coating decreased firstly and then increased. The minimum of the maximum of shear stresses was achieved at 0.4 ram. Secondly,with the increase in the thickness, the suddenly changed stress of coating/substrate along the Z axis decreased, while the suddenly changed stress in coating along the Z axis increased. However the position of the suddenly changed stress in coating along the Z axis was transformed to the external surface of the coating. Finally,the increase in the thickness of coating contributed to the decrement of the stress along the X axis.