Influência da tensão de deposição de intercamada contendo silício a partir de tetrametilsilano para a adesão de carbono amorfo hidrogenado em substratos ferrosos

Abstract

Energetic losses by friction represents a meaningful portion of the global produced energy. On the other hand, new technologies and materials are constantly developed by the scientific community. Diamond-like carbon, known as DLC, is one of these materials, standing out for the properties of low friction coefficient, high hardness and chemical inertness. The sp² and sp³ carbon and hydrogen content of this material influences its properties. Therefore, there is different subdivisions for the DLC, such as hydrogenated amorphous carbon (a-C:H), amorphous carbon (a C), tetrahedral carbon (ta-C), among others. The DLC film application implies a scientific challenge: the low adhesion on ferrous substrates. There is, currently, strategies to avoid this problem, such as, for example, the usage of an interlayer: a film situated between the DLC and the steel in order to promote adhesion. This work used plasma-enhanced chemical vapor deposition (PECVD) to deposit silicon-containing interlayers from tetramethylsilane (TMS) applying different voltages to improve DLC adhesion in AISI 4140 steel samples. Raman spectroscopy, scanning electron microscopy (SEM/FEG), energy-dispersive X-ray spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES), Fourier-transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) techniques were used to characterize the coatings. Scratching tests were performed in a tribometer. It was found that the interlayer thickness increase from 400 to 600 V and decreases from 600 to 800 V. To explain this behavior, it is proposed a mechanism involving ionization, sputtering and dissociation. An increase in the voltage also causes the carbon content to raise in deeper regions of the interlayer and lower on the shallow ones, as well as contribute to the aggregation of oxygen on this interface. This behavior is attributed to the carbon ionic implantation that is favored by the TMS dissociation in the plasma. The most well adhered coatings were produced using 400 V on the interlayer deposition, possibly due to the higher silicon content in the interlayer/steel interface. [resumo fornecido pelo autor]