The Study On DLC Films Deposited By Pulse-PECVD

In the study,DLC films were deposited successfully on the wafer,316 L stainless steel,and YG8 cemented carbide by using pulse-plasma enhanced chemical vapor deposition(Pulse-PECVD).In the process of deposition under the precursor C2H2 and the auxiliary gas Ar,the mesh cage was adoped to further enhance plasma and significantly increase the deposition rate of the films.The effects of the processing parameters including working pressure,C2H2 flow rate and operating voltage on the micro-structure and mechanical properties of DLC films were investigated.The surface morphology and thickness of the films,bonding strength,structure,mechanical and tribological properties of DLC films were analyzed by AFM,Raman spectroscopy,nano-indenter,profilometer and so on.The results show that the deposition rate increases with the increase of working pressure and C2H2 flow in the case of the semi-cage bound structure.The elastic modulus and nano-hardness of DLC films deposited on two kinds of substrates are higher when C2H2 flow is 60 SCCM,Ar flow is 20 SCCM and the deposition pressure is 2Pa.The hardness and modulus of the films on the 316 L stainless steel substrate are 16.1GPa and 152.8GPa respectively,and the values on YG8 cemented carbide substrate correspond to 17.2GPa and 170.6GPa;At the same time,ID/IG in Raman spectroscopy of the above film with the characteristics of a typical DLC,is the smallest,and consistent with the mechanical properties;Moreover,the friction coefficients of the above films prepared on the substrates of stainless steel and cemented carbide are 0.206 and 0.209,respectively,that are smaller than other films.With the increase of operating voltage,the deposition rate,hardness and elastic modulus of the films deposited under the condition of the whole net cage structure increase,and the films' roughness and friction coefficient decrease.When the operating voltage is 3k V,the hardness and elastic modulus of DLC films on stainless steel substrate are 15.4GPa and 141.2GPa respectively,and the friction coefficient is 0.215;The corresponding values on the cemented carbide substrate are 15.7GPa?149GPa and 0.218,respectively;Meanwhile,Raman spectroscopic analysis of the films also shows that the ID/IG is the smallest,which is also consistent with mechanical properties.The bonding strength between DLC films and substrates is still not very satisfied;The bonding strength of DLC films prepared on cemented carbide substrate and stainless steel substrate falls within the range of 24~40N and 4~18N,respectively.The adhesion of DLC films deposited on cemented carbide substrate is generally superior to that of stainless steel substrate,which is related to the residual stress of the films,and difference of the mechanical properties between the substrate and the film.Through the exploration and optimization of deposition process,DLC films with excellent mechanical properties are prepared and the deposition rate is fast.To further improve the working voltage and change the proportion of C2H2 gas in mixed gas is expected to obtain the comprehensive performance of the DLC films.However,further study is needed to reduce the residual stress in the films and improve the adhesion between the films and substrates,which is expected to provide the better support for industrial application.