Study on the advanced evaluation system of the coating layrs

涂层的力学特性通常通过使用几毫克量级的微载荷进行超微硬度测试来评估。而超微硬度则受软基体变形、沉积后冷却过程中产生的拉伸残余应力以及层与基体之间的界面强度的影响。因此，本研究发展了数值和实验方法来阐明影响超显微硬度的因素。（78）采用三维弹塑性有限元法和三维分子动力学方法建立了涂层力学特性评价模型。将超显微硬度试验的宏观有限元模型应用于涂层和基体的应力和变形分析。通过比较不同厚度涂层的压痕深度与硬度之间的关系，得到了硬质涂层超显微硬度测试的压痕深度极限。采用微观分子动力学模型对涂层与基体界面晶格缺陷对显微硬度的影响进行了评价。界面中的点阵缺陷会降低合金的显微硬度。在超显微硬度中，压头尖端的圆度是不可忽略的。为此，制备了尖头压头和圆头压头，用这两种压头进行压痕实验。用圆头压头获得的硬度与用尖头压头获得的硬度有很大的不同。最后提出了用圆头压头测量硬度的校正方法。(70)

The mechanical characteristic of the coating layrs is often evaluated by the ultra microhardness test using a micro load of the order of a few milligrams. The ultra microhardness, however, is affected by the deformation of the soft substrate, the tensile residual stress caused during the cooling after the deposition, and the interface strength between the layr and substrate. Thus the numerical and experimental methods which clarify the factors affecting the ultra microhardness were developed in this study. (78)The modeling for evaluating the mechanical characteristic of coating layrs were developed using three dimensional elastic plastic finite element method and three dimensional molecular dynamics. The macroscopic finite element modeling of the ultra microhardness test is applied to the analysis of stress and deformation of the coating layr and substrate. The limit of indentation depth in the ultra microhardness test of the hard coating layrs was obtained by comparing the relationship between the indentation depth and the hardness of the coating layrs of different thickness. The microscopic molecular dynamics modeling of the test is applied for evaluating the influence of the lattice defects in the interface between the coating layr and the substrate on the ultra microhardness. The lattice deffects in the interface always reduce the ultra microhardness. (128)The roundness of the tip of the indenter is not negligible in the ultra microhardness. Thus a sharp tip indenter and a round tip indento were prepared to conduct the indentation experiments with these two indentoers. The hardness obtained with the round tip indentoer was quite different from the hardness with the sharp indenter. Finally the correction method of the hardness measured with a round tip indenter was proposed. (70)