Síntese e caracterização de filmes finos de Ti-Cr-Si-N sobre aço aisi 4340: aumento de dureza e da resistência ao desgaste

Abstract

The aim of this work is the synthesis and characterization of Ti-Cr-Si-N thin films obtained by the cathode roller method. Thin films are layers of material between nanometers and micrometers thick that are deposited on a substrate to modify its surface properties. These properties can be optical, chemical, electrical, mechanical, magnetic and thermal, depending on the type of film and the application. In the field of mechanics, thin films can increase the wear and corrosion resistance of materials, so the substrate used in the research was AISI 4340, due to its importance in mechanical manufacturing. The cylinders used as cathode targets were made from a mixture of titanium, chrome and silicon powders pressed in a compaction matrix. The nitriding reactor with the modified cathodic cage method or cathodic cylinders (CCyPD) was used to carry out the deposition treatments. The depositions were made at two types of potential: cathodic and floating, at temperatures of 300, 350, 400 and 450 °C. In the cathodes with two proportions of gases (N2-H2): 80-20% or 20-80%. Subsequently, the films deposited on the treated samples were characterized by X-ray diffraction (XRD) and Raman spectroscopy. A hardness test was carried out. The dry pin-disc wear test, SEM with EDS, and profilometry to evaluate the wear track were also carried out. The results showed that the type of treatment potential (cathodic or floating) influenced the formation of some phases. The diffractogram showed that the crystallinity of the phases increased with the treatment temperature in the samples analyzed. XRD and Raman showed the synthesis of nitrides on the surface of the substrate. The hardness tests showed that the hardness increased by at least 70% compared to the substrate at a ratio of 20-80% (N2-H2). The formation of nitrides, which are very hard materials, on the surface of the samples explains this increase in surface mechanical properties. The wear track region generated by the tribological pin-disk test was analyzed in terms of the profile on the surface of the samples. Compared to the untreated substrate, the treated samples showed greater roughness and greater resistance to pin wear. The cathodic samples showed higher hardness values and lower wear track depth values, particularly the 400°C treated sample, which showed 2349HV and 2.5μm.