Study On The Adhesion And Load-bearing Capacity Of Diamond-like Carbon Films On The Ti6Al4V Substrate

In this paper,the interface properties of TiO₂/?Si,Ti,Cr?/DLC film is analyzed by first-principles calculation.The DLC films with different interlayers?Si,Ti,Cr?were prepared on the Ti6Al4V substrate by magnetron sputtering.The effect of interlayer on adhesion of DLC film on titanium alloy surface was studied.Secondly,the stress concentration of DLC films on the titanium alloy were simulated by finite element method.The multilayer DLC films were prepared on the titanium alloy by plasma chemical vapor deposition?PECVD?.The relationship between multilayer structure and load-bearing capacity is studied.The main conclusions are as follows:?1?The first-principles calculation results of TiO₂/?Si,Ti,Cr?/diamond showed that the adhesion work of O termination in TiO₂/Si model is 5.31 J/cm²,5.22 J/cm² and 1.32J/cm²,the interface bonding strength is Si-O>Si-Ti>Si-Cr.For the?Si,Ti,Cr?/diamond model,the interface adhesion work of Si/diamond,Ti/diamond and Cr/diamond is 9.15J/cm²,7.25 J/cm² and 4.40 J/cm² respectively,and the bonding strength at the interface is C-Si>C-Ti>C-Cr.So,it can be concluded that the bonding strength of the TiO₂/Si/diamond interface structure is the strongest among the three transition layer films.This is consistent with the calculation result of the first principle.?2?The experimental results of Ti6Al4V/?Si,Ti,Cr?/DLC films prepared by magnetron sputtering show that:the internal stress of the films with Si,Ti and Cr were-1.45 GPa,-1.57 GPa and-1.72 GPa,respectively.The Si interlayer films had the lowest stress.The scratch results showed that the critical loads of Si,Ti and Cr interlayer films were 18.1 N,15.3 N and 12.5 N,respectively.Therefore,the adhesion of Si interlayer film is the strongest,which is consistent with the calculation result of the first principle.?3?The stress distribution of four multilayer DLC films with different periods?15 P,20 P,30 P,50 P?on the titanium alloy was calculated by finite element method.The results showed that under low load?indentation depth of 500nm?,under low load?indentation depth of 500 nm?,the maximum radial stress of multilayer films of 15,20,30 and 50periods first decreased and then increased,which are-9387.26 MPa,-9224.64 MPa,-9243.71 MPa and-9233.25 MPa,respectively.The variation trend of equivalent stress and shear stress was similar to that of radial stress.Therefore,the 20 periods multilayer film has a higher load-bearing capacity.However,under high load?indentation depth of3000 nm?,the radial stress,equivalent stress and shear stress of the multilayer film with increasing period gradually decrease,that is,the load-bearing capacity of the multilayer film increases with increasing period of the film under high load.?4?The study of multilayer high Si doped DLC/low Si doped DLC films with different periods prepared on the titanium alloy by PECVD method showed that the internal stress decreased with the increase of film period.The internal stress of 15 period,20 period,30 period and 50 period multilayer films is-0.98 GPa,-0.80 GPa,-0.77 GPa and-0.49 GPa respectively.The film of 50 periods had the maximum hardness?12.6 GPa?and young's modulus?106.1 GPa?.The critical load of DLC film increased with the number of periods.The vickers hardness morphology played that the number and propagation range of cracks in 20 period films are the smallest under the load of 500g,and the number and propagation range of cracks in 50 period films were the smallest under the load of 1000g.Therefore,the load-bearing capacity of 15 periods and 20 periods films is better under low load,and that of 30 periods and 50 periods films is higher under high load.The experimental results are consistent with the results of finite element simulation.