Estudo das Propriedades Tribológicas e Mecânicas do filme DLC multicamadas dopadas com nitrogênio

Abstract

Diamond-like carbon (DLC) films have excellent mechanical properties but have difficulties in adhering to metallic surfaces. Nitrogen doping in the structure of DLC films provides better adhesion of the film to the substrate, while the application of multilayer films can improve the mechanical properties of the films. The objective of this work is to carry out the deposition of DLC film in the monolayer and multilayer arrangement and to verify the influence of nitrogen doping on the mechanical and tribological properties of the DLC film deposited on the AISI 321 H stainless steel substrate, using the PECVD deposition method with DC-Pulsed source. For the deposition of the DLC film, a plasma ablation cleaning of the metallic substrate was performed with 80%Ar and 20%H2, then an organosilicon interlayer was deposited with 70%HMDSO and 30%Ar, and finally deposited the DLC film was deposited using 10%Ar and 90% CH4. In the deposition of nitrogen-doped DLC (DLCN), after cleaning the substrates by ablation and deposition of the interlayer, 70% CH4 and 30% N2 gas was used for film deposition. The multilayer films were deposited by varying the ordering of the DLC and DLCN films. A gradient deposition of the nitrogen-doped DLC film was also performed. The films were characterized by visual analysis, analysis of the physical-chemical structure evaluated by metallographic via SEM and EDS, Raman spectroscopy and infrared spectroscopy, adhesion test by Rockwell C hardness, wear resistance, nanohardness test and scratch test. The monolayer DLC and DLCN films demonstrated uniform layers, with bands in the Raman and infrared spectra characteristic of the film. All depositions exhibited high wear resistance compared to the base material. The DLCN film showed superior adhesion compared to the DLC film, with similar hardness and modulus of elasticity between the films. In the deposition of the multilayer films, an acceptable adherence to the substrate was obtained, with an increase in wear resistance in relation to the substrate, but with the formation of defects in the film due to the drop in temperature that occurred during the treatment steps. The DLC film deposited in gradient showed the best adhesion and wear resistance results, maintaining hardness similar to the DLC and DLCN films, explained by the synergy of properties of the DLCN and DLC films deposited sequentially. It is concluded that DLC films significantly improve the tribological and surface mechanical properties of the material studied, the multilayer DLC films deposited without external heating present defects and gradient films proved to be an alternative to increase the film properties while maintaining good adhesion to metallic substrates.