AlTiN涂层合金划痕测试的失效形式及其失效机理的有限元分析

为了研究硬质合金基体中硬质相和粘结相对涂层内聚失效抗力(LC1)和膜基结合力(LC2)的协同作用,设计制备了具有硬质相+粘结相两相结构的WC-10Co-0.65Cr_3C_2-0.35VC(10Co)、无金属粘结相WC-6Mo_2C-0.68Cr_3C_2-0.37VC(bWC)和无硬质相85.1Co-9.2W-4.7Cr_3C_2–1.0VC(CoW)合金。采用直流磁控溅射技术,在上述合金基体表面分别沉积了厚度约5μm的Al0.55Ti0.45N薄膜。通过划痕测试获得的LC1和LC2及其差值,对涂层的失效形式进行了表征。通过划痕测试过程中涂层应力分布的有限元分析,研究涂层合金划痕失效形式所对应的形成机理。在此,LC1对应涂层首次被剥离或基体首次被暴露时所对应的载荷,与涂层的内聚失效抗力呈正相关关系;LC2对应涂层被完全从基体剥离时的载荷,表征涂层合金的膜基结合强度。在此基础上,进一步研究WC–Co合金基体中WC晶粒度和Co含量对涂层合金划痕测试过程中涂层中应力分布的影响。结果表明,采用软质CoW合金基体,涂层的LC1和LC2均为最低;采用硬质bWC合金基体,涂层的LC2最大,但LC1和LC2差值也最大;采用10Co合金基体,涂层的LC1最大,LC1和LC2差值最小。涂层与基体的杨氏模量比和基体硬度是影响LC1和LC2的关键因素。降低硬质合金基体的晶粒度,选择适中的Co含量,均有利于LC1和LC2的同步改善。

Structure design of gradient hard coatings on YG8 and their residual stress analysis by ANSYS

A structure of gradient hard coatings( Ti,TiN,TiCN and TiAlN) is designed,and residual stress is simulated by a finite element method with ANSYS. The influence of the realistic situation including load and temperature on the residual stress of the coatings is investigated. Simulated results show that the realistic situation strongly affects the residual stress. To be specific,i) The main residual stress concentrates on the coatings prepared on YG8 substrate,and the residual stress and its gradient of the coatings are bigger than that of the substrate; ii) TiAlN and TiCN coatings have better resistance compression than that of TiN coatings in the same condition; iii) The improved multilayer structure of the gradient hard coatings produces weaker residual stress but higher anti-pressure of the substrate.