Microestrutura e propriedades de desgaste e corrosão de revestimentos à base de FeCrMoNbB e de CrCoNi produzidos por plasma com arco transferido

Abstract

The application of protective coatings on components requiring resistance to wear and corrosion has been widely investigated. However, achieving surfaces that simultaneously combine high resistance to both phenomena is a significant challenge. In this context, selecting the appropriate alloy system and processing method for coating production is essential. The present study aimed to investigate metal coatings processed by Plasma Transferred Arc (PTA) using two alloys with distinct microstructural characteristics to achieve specific properties. The alloys studied were: an Fe-based alloy (Fe68Cr8Mo4Nb4B16) and a multiprincipal element alloy (Cr40Co40Ni20). The PTA technique has proven effective in producing coatings with excellent wear and/or corrosion resistance properties, in addition to allowing the production of thick, dense coatings with good metallurgical bonding between the substrate and the coating. The two alloys were gas-atomized and subsequently characterized by scanning electron microscopy (SEM), optical microscopy (OM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC, for the glassy alloy powder). The PTA-produced coatings were characterized by XRD, SEM, OM, transmission electron microscopy (TEM), ASTAR (automatic crystallographic orientation mapping system), and confocal microscopy (CM). Vickers microhardness was measured on the top of the polished coatings. Tribological tests were conducted according to ASTM G133-05 standards on polished surfaces (Al2O3 1-μm) using a reciprocating pin-on-plate configuration. Electrochemical tests included the analysis of potentiodynamic polarization curves and electrochemical impedance spectroscopy in a 0.6M NaCl electrolyte. The results indicate that the PTA-produced coatings, using alloys with innovative microstructures, provide good tribological and/or electrochemical properties.