梯度结构对氧化铝陶瓷涂层接触应力的影响

Influences of Gradient Structure on Contact Stresses of Al_2O_3 Ceramic Coatings

采用幂指数描述"三明治"式梯度结构形式,建立镍基氧化铝梯度陶瓷涂层在静态接触集中力载荷作用下有限元模型,分析静态接触集中力载荷作用下涂层的Mises应力分布,以及梯度层的厚度、中间层数及结构形式对涂层的Mises应力分布及最大Mises应力发生位置的影响。结果表明:梯度结构对接触区Mises应力大小及分布影响不大,但影响最大Mises应力发生位置;合理的梯度结构能避开最大Mises应力发生在表面强化区及梯度区中,防止陶瓷涂层在接触载荷作用下疲劳脱落。制备层状结构梯度陶瓷涂层时,采用氧化铝层厚度20μm、线性梯度层厚度80μm、8层中间层,可改善Mises应力,适当避开最大Mises应力发生在梯度区。

An elastic-plastic finite element numerical model for gradient coatings with sandwich structure was formulated to study Mises stresses distribution at Al2O3 gradient ceramic coatings during contact load.The influence of structure parameters such as the layout of interlayer/metal, the thickness of gradient coatings on the Mises stress distribution and the position of maximum Mises stress was analyzed.The results show that the gradient structure has less influence on the size and distribution of Mises stress,while has some influence on the position of the maximum Mises stress.The reasonable gradient structure can avoid the maximum Mises stress to appear in the surface hardening.zone and the gradient zone, and can pre- vent the ceramic coating from falling off under the contact load.A gradient structure with Al2O3 layer thickness of 20μm, linear gradient layer thickness of 80μm and 8 interlayers was proposed, which can improve the Mises stress, and avoid the maximum Mises stress to appear in the gradient area properly.