Preparation And Application Of Multilayer Diamond Coating Based On HFCVD Method

In the industrialization goal of diamond coating,improving the quality of the diamond coating,the bonding force between the coating and the substrate have become the core of the development of diamond coating products.With the advancement of the mechanical industry,the research perspective of thin films has been continuously enlarged,from micro crystalline diamond(MCD)to nanocrystalline diamond(NCD).Based on the above research background and purpose,Hot Filament Chemical Vapor Deposition(HFCVD)was used to prepare multi-layer diamond coatings with different structures in this article.Scanning Electron Microscope(SEM),Raman spectrometer,Atomic Force Microscope(AFM),nanoindentation tester were used to characterize the films’ macroscopic,microscopic morphology,composition,internal stress and other properties.In this paper,the multilayer coating indentation stress distribution was compared and analyzed by ANSYS finite element simulation software,and the relationship between the anisotropy stress and the coating structure was obtained.Secondly,the coating deposition process parameters were optimized by orthogonal test.The multi-layer diamond coating was prepared and its quality was characterized.Based on the previous theory and experimental preparation,the multilayer coating was applied to the tool for cutting wear analysis.The main research contents are as follows:(1)The indentation model of multilayer diamond coating was established based on ANSYS finite element simulation software.The axial and radial stress states of bilayer,triple and fivefold layer were compared and analyzed.The relationship between coating structure and stress distribution was studied.Triple with less stress mutation and better stability were selected to investigate the stress distribution of each layer.It provided a theoretical basis for the failure of subsequent coating under stress.(2)In order to improve the internal bonding force of the coating and reduce the surface roughness,a structure design scheme of multi-layer diamond coating was proposed.The optimal horizontal process parameters were obtained by the orthogonal experiment of four levels and three factors.Bilayer,triple and fivefold layer diamond coatings were deposited under the process parameters.The surface morphology,grain composition,internal stress and surface roughness of the coating were characterized and analyzed.Through characterization test,it was found that gradient refinement could effectively improve interlayer bonding and reduce internal defects.The relative thickness of NCD reduces the surface roughness.(3)According to the optimum process parameters,triple-layer was prepared with 1% and3% methane concentrations.The experiment of cutting white marble with triple-layer diamond coating tool was carried out by applying diamond coating tool to ball end milling cutter.The cutting wear morphology of coating tool was characterized and observed.Based on the relationship between the coating structure and the stress distribution,the theory and results of the coating tool wear mechanism were analyzed.It was found that the blade wear band widens with wear time.The damaged surface can be divided into three states: partial shedding,total shedding and bonding area.Different degrees of peeling,bonding and cracking appeared.