脆性涂层对韧性基体的损伤行为和演化机理

This proposal aimed at studying the brittle-coating-ductile-substrate system, exploring the stress gradient evaluation rules and stress release process of coatings by in-situ X-ray stress evolution device, realizing quantitative cognition of coating crack nucleation and growth, uncovering the brittle coating induced ductile substrate damage behavior and mechanisms by modern micro fracture zone preparation and observation methods and high throughput coating induced substrate damage experiment method, hoping overset the traditional view that brittle coatings protect ductile substrate, and providing perspectives and ideas for coating-substrate system structure and properties. Hoping to achieve the following objectives: 1) give the influence rules of interface adhesion, loading rate, tensile or compressive stress and value on crack growth along the interface; 2) establish the quantitative relation between coating residual stress, loading value, loading rate and coating induced substrate damage; 3) illuminate the coating induced substrate damage behavior and mechanism by observing the fracture microstructure.

本申请以广泛应用的脆性膜层-韧性基体为研究对象，利用X射线原位应力演化装置研究膜层中应力梯度演化规律及应力释放过程，实现膜层中裂纹形核和扩展的量化认知，辅以现代微区断口的制备和观察手段，结合膜致基体损伤高通量实验技术，揭示脆性膜层对韧性基体的损伤（脆性开裂或局部变形）行为和机理，颠覆传统观点“脆性膜层对韧性基体保护性”的认知，为膜-基体系的结构、性状设计提供新的视角和思路。拟达到如下目标:1）给出膜-基界面结合强度，加载速率，拉、压载荷及大小对膜中裂纹沿界面扩展的影响规律；2）建立膜中残余应力，拉、压载荷大小及加载速率对膜致基体损伤（脆性开裂或局部变形）的定量关系；3）通过膜致基体开裂断口的微结构观察，阐明膜致基体开裂的行为和机理。

脆性涂层一方面能改善金属基体表面状态，一方面因其较低的断裂韧性对基体易造成损伤。本项目研究了脆性涂层致韧性基体开裂的起源、发生机制以及相应的预防措施，为带有涂层的工程结构件的安全服役提供了理论参考。脆性涂层的开裂可以造成韧性基体的解理开裂；涂层-基体的短程交互作用以及涂层的开裂(引入高速运动的裂纹)可以抑制近表面基体的塑性变形，从而导致韧性基体的解理开裂；基于能量守恒原理，涂层越厚，涂层开裂后所释放的弹性应变能越大，导致裂纹在基体中的扩展距离越长，从而更显著地降低基体的韧性以及疲劳性能。在此基础上，提出了硬质涂层的增韧方法以降低裂纹扩展速度，大大减缓了涂层开裂对韧性基体损伤。在该基金支持下累计发表论文21篇,其中SCI收录19篇。培养博士研究生7名，其中已经毕业3名；硕士研究生6名，其中已经毕业5名。