Nanoindentation Characterization Of Mechanical Properties For Plasma Alloying Coating On316L Stainless Steel

Thin film technology is a kind of common surface treatment technology, a layer of thin film materials with special physical and chemical properties was prepared on the matrix surface, which can enhance the performance of the matrix and meet the needs of using. Film preparation process directly affects the performance of the film, the films prepared by the same material but different fabrication processes have obvious different performances. During properties of the film material, the mechanical properties of thin film material affect its using and life span, thus it is crucial to determine mechanical properties. Among the mechanical properties tests, the hardness of film and combined performance between film and base are the most attention. Hardness, which reacting the ability of the film material resistance to compression capability, has the significant influence on wear resistance of the film. Film bonding properties were directly related to the use life of film materials and the premise of the practical application. This paper firstly introduced research background and status of the topic, made a simple introduction to the methods for measuring thin film material mechanics performance. And the detailed narration for the nanoindentation method of measuring material mechanics performance was made. Then we tested and researched the mechanical properties of Ti, TiN and TiO2modified layers, which were prepared on the316L stainless steel substrate surface by the plasma surface alloying technology. Using the continuous stiffness method, nanoindentation experiments were tested on the specimens, obtains the changing curves of load, hardness and elastic modulus with pressure depth on different directions of three kinds modified layers and substrate materials. Comparing the properties of three kinds modified layer and the matrix on different directions, obvious anisotropy were presented. Compared three different directions was studied, the mechanical properties of thin film and the substrate, both present obvious anisotropy. The three kinds modified layers materials all have higher hardness than316L stainless steel body material in different directions. The TiN modified layer has the best mechanical properties. For Ti modified layer and TiO2modified layer, the measuring value of hardness and elastic modulus close on the surface direction, while on the cross section direction the hardness and elastic modulus with pressure depth change curves approximate parallel. Finally, we used the ANSYS finite element analysis software, choose double linear reinforcement material model, structured two-dimensional indentation experiment model, and estimate the parameters of the material, made a large number simulations by the displacement control method. The simulation results were analyzed by using the dimensional analysis method. We established the dimensionless function, brought the test results in to the function, and calculated the function in the experiment conditions. Film material stress strain relation was acquired finally. Substituting the deduction results simulate once again, the simulation results and experiment parameter curves agree well. Simulating by using the deduced material parameter with the force loading control method, analyzing the results we can qualitative judge the TiN modified layer bonging strength is significantly better than that of the Ti modified layer, these analysis results conform to scratch tests.