Caracterização de TiCN para aplicação em revestimentos de elevada dureza em alternativa ao revestimento metálico

Abstract

Coatings are an effective engineering solution to improve the surfaces of materials that face severe conditions of wear, corrosion, erosion, thermal deterioration and other surface degradation phenomena. This work studied a ceramic composite material to be used as a high-hardness coating, as an alternative to the metallic coatings already existing in engineering. Titanium Carbonitride (TiCN) was chosen for the development of the research and characterized in its pure form and also with the addition of 0.5% graphene nanoparticles, after sintering at three different temperatures (1600°C, 1700°C and 1800°C). The procedures of sanding, polishing, optical microscopy (OM), digital image processing (DIP), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy and Vickers microhardness test (HV) were performed. In turn, the existing metallic coating chosen for comparative analysis, a Fe–Cr-B-Mn alloy deposited by thermal spraying (TA) on a metallic substrate, was characterized by erosion testing, optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and roughness testing. Both materials were then subjected to the Pin-on-Disc wear test and analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The TiCN sintered at the highest temperature, 1800°C, showed the best performance in the wear test among all the specimens tested, of both materials. Both in its pure version and with the addition of graphene, it showed negligible loss of mass and thickness. Its performance was slightly superior to that of the metallic coating, which, in turn, showed a small loss of thickness. The EDS and XRD analyses corroborated the chemical composition of the TiCN. The MO and SEM images showed that the porosity of TiCN decreased with increasing sintering temperature in the pure samples, while the addition of graphene nanoparticles presented benefits in densification only in the specimens sintered from 1800°C. The microhardness analysis showed that this TiCN sintered at a temperature of 1800°C presented higher hardness, 2100 HV, due to higher densification and lower porosity. The presence of pores in this group of samples was 6.65% for the pure sample, and 3.90% for the specimen with graphene addition. Both values are lower than the porosity presented by the Fe–Cr-B-Mn metallic coating obtained by AT, of 14.9%. This coating also presented microhardness of 754 HV, lower than those presented by TiCN samples A1, B1 and C1.