Study On Residual Stress Of Thin Films By Nanoindentation Technology

Due to the properties of excellent wear and corrosion resistance,coatings are applied to various areas.But differents between coating and substrate lead to the residual stress in the film,which is important on adhesive strength,anti-fatigue and wear-resisting property.On the other hand,residual stress result in cracking and peeling on the surface of coating.Research on the size and distribution of residual stress in layer is important to further study the cause of residual stress.Ti film and its multi-layer film are materials with high strength and excellent anti-corrosion performance,which play an important role in fields of military and aerospace.In our study,Ti film was deposited by the direct current(DC)magnetron sputtering and the Ti N and Ti/Ti N multi-layer film were plated by reaction magnetron sputtering technique as well.Different preparation processes were explored to study on the properties of thin films.Scanning electronic microscope(SEM),Transmission electronic microscope(SEM),X-ray Diffraction(XRD),electronic Film Stress Distribution Tester and nano-indentation tester were used to detect the morphology,the phase structure,the residual stress and nano-mechanical properties of the films respectively.The crucial part of this paper focus on residual stress of films using nano-indentation and electronic Film Stress Distribution tester.The finite element analysis(FEM)was used to simulate the nano-indentation process to obtain the true plastic properties and the stress distribution of films.The best process parameter of Ti and Ti N films prepared by magnetron sputtering were determined through exploreing the effect of films on the performance.The Ti film residual stress results showed that the residual stress value obtained by Suresh model was almost the same as that by the curvature method,so the Suresh model was more suitable for calculating the residual stress of films.Though nano-indentation data and curve method analysis,it was found when the film thickness of 1.2 μm,nano-indentation depth: 150 nm the residual stress of thin film is accurate result.Simulating the process of nano indentation test,it was found that significantly bulge in the Ti/Ti N multilayer film.For the same thickness of single phase Ti film and hard Ti N film the film’s bulge phenomenon is not obvious with the same pressed depth.The residual stress in the Ti/Ti N multilayer film is lower than that in Ti and Ti N films.