Interfacial Mechanics Analysis of a Brittle Coating–Ductile Substrate System Involved in Thermoelastic Contact

Chi Zhang,Le Gu,Chuanwei Zhang,Liqin Wang,Chongyang Nie

doi:10.3390/coatings7020021

Abstract

In this paper, interfacial stress analysis for a brittle coating/ductile substrate system, which is involved in a sliding contact with a rigid ball, is presented. By combining interface mechanics theory and the image point method, stress and displacement responses within a coated material for normal load, tangential load, and thermal load are obtained; further, the Green’s functions are established. The effects of coating thickness, friction coefficient, and a coating’s thermoelastic properties on the interfacial shear stress, τxz, and transverse stress, σxx, distributions are discussed in detail. A phenomenon, where interfacial shear stress tends to be relieved by frictional heating, is found in the case of a coating material’s thermal expansion coefficient being less than a substrate material’s thermal expansion coefficient. Additionally, numerical results show that distribution of interfacial stress can be altered and, therefore, interfacial damage can be modified by adjusting a coating’s structural parameters and thermoelastic properties.

Highlights

Today, the key elements, such as bearings and gears, are under great pressure to meet the legislative demands of long life and high operational speeds [1,2,3]
The key elements, such as bearings and gears, are under great pressure to meet the legislative demands of long life and high operational speeds [1,2,3]. These challenges can be achieved by employing high hardness, anti-corrosion, and wear-resistant brittle coatings, such as metal nitride coatings, metal oxide coatings, diamond-like carbon (DLC), etc., to protect working surfaces, as well as adopting high strength steel [4,5]
The huge mismatch between coatings and steel substrates in thermoelastic properties always leads to interfacial stress concentrations, which are induced thermally and mechanically, increasing the risk of coating delamination

Summary

Introduction

The key elements, such as bearings and gears, are under great pressure to meet the legislative demands of long life and high operational speeds [1,2,3]. Induced deformation, subsequently, changes the Hertzian little attention has been paid to the interfacial stress distributions of coated solids involved in stress distribution of coated materials from the surface to several micrometers in depth, especially for thermoelastic contacts. Induced deformation, to fulfillsubsequently, a thoroughchanges optimization of a stress harddistribution coating–substrate system, from it is the necessary establish an the Hertzian of coated materials surface totoseveral interfacial stress analysis for for thermoelastic micrometers in depth,model especially hard coatings,contacts. The Green’s functions of the stress and displacement fields of aim of exploring waysfor to areduce risks of delamination of hard coatings from steelWith substrates, the coated materials normalthe force, tangential force, and thermal loading are established. Be strongly related to the propagation of interface cracks in hard coating–substrate systems [18,19,20]

Description of the Thermoelastic Contact Model

Schematic description gapbetween betweensurface surface elements

Procedure procedure can be conducted as follows:

Discussion

13. Distributions

Conclusions