Study On Synthesis And Mechanical Properties Of Diamond-like Carbon Multilayer Films On Aluminium Alloy

Using the unbalanced magnetron sputtering deposition (UBMS) and microwave electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD), DLC/Ti,DLC/TiN/Ti,DLC/Si multilayer films were successfully synthesized on the super-harden aluminium alloy. In order to enhance the interface bonding strength between the film and Al alloy substrate, Ti,TiN/Ti and Si films were firstly fabricated as the buffer layers on Al alloy substrate by UBMS. The reactant gas was Ar-C2H2 for depositing the DLC films. The morphology and microstructure of the films were studied with scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and laser Raman spectroscopy et. The mechnical and friction properties were tested by microhardness, scratech testing and ball-on-disk wear testing. The corrosion resistance was measured in a 0.9% NaCl solution at room temperature. The main results of this paper are as follows:(1) The functionally graded DLC films deposited on Al substrate that have been pre-deposited with TiN/Ti interlayer show excellent mechanical characteristics. TiN interlayer was prepared by UBMS and the effects of the bias and thickness on the properties of the functionally graded DLC films. TiN interlayer deposited by DC bias had the higher hardness, good wear resistant and interlayer bonding strength compared with plused bias. In addition, the TiN interlayer deposited about the thickness of approximately 250nm acts as the buffer layer to attain excellent mechanical properties.(2) The deposition plused bias of DLC film was discussed in DLC/Si/Al multilayer films.With the negative bias increased from-150V to-1000V, the sp3 bonded carbon content decrease, the hardness and internal stress decrease also, fracture toughness increase. The results show that DLC films preparesd by the higher deposition have weak wear resistance and adhesive strength. DLC film deposited under negative bias of-150V was superior to others. It was observed that the tribological properties of the DLC/Si/Al films not only to the content of the sp3 bonding, but also the effect of hydrogen content of DLC films.(3)The effects of interlayer types(Ti,TiN/Ti,Si) in bonding structure, mechanical properties and corrosive resistance of DLC films were studied. This indicates that the sp3 and sp2 bonded carbon content of DLC deposited on different interlayers were not obvious difference. The mechanical properties including hardness, fraction toughness, critical load and wear resistance, of DLC films can be improved by deposited Si multilayers compared with others. In addition DLC/Si/Al multilayers showed the high free corrosion potential and good morphology of corrosion. Use of the press-the tensile-friction tools appraisal method, we semiquantitative evaluated that the lower friction force, excellent lubricant and higher interface adhesive strength of DLC/Si/Al multilayers.In this paper "the interlayers+DLC deposition" the dual surface modification technology achieved to improve the role of mechanical properties of Al alloy. The modification methods of DLC/Si/Al multilayer film system has a potentially application value.