Estudo do efeito do teor de diferentes reforços (WC E NbC) e da moagem de alta energia nas propriedades mecânicas e elétricas dos compósitos com matriz metálica de cobre

Abstract

Composites designed with a copper matrix reinforced with ceramic and refractory materials are promising for use as electrical conductors due to their combination of excellent thermal and electrical properties, and the high mechanical resistance to wear. Several researchers have explored the addition of different reinforcements in manufacturing composites to enhance these properties. This study aimed to investigate the applicability of two types of reinforcements (WC and NbC) in copper metal matrix composites fabricated using powder metallurgy and Spark Plasma Sintering (SPS) in electrical contact application. The study evaluated variables such as composition (type of reinforcement and concentrations of 5% and 20% by mass) and processing (with milling times of 5, 10, and 20 hours). Analyses were conducted using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Fluorescence (XRF), and X-ray Diffraction (XRD) with Rietveld refinement. Mechanical properties were assessed through Vickers microhardness testing. The microscopy analysis of the composite powders revealed that the Cu particles were severely deformed, forming plates, while the ceramic particles (WC and NbC) were fragmented and incorporated into the Cu phase due to high-energy milling. XRD analysis showed characteristic peaks of the composites, with increased Full Width at Half Maximum (FWHM) values, reduced crystallite sizes, and increased microdeformation of the phases. XRF analysis indicated potential contamination of the composite powders due to the milling conditions. The microstructural analysis indicates increased composite porosity as the reinforcement content and milling time increase. A significant increase in average Vickers microhardness values was noted for nearly all the composites compared to pure Cu. Notably, the composite with 20% by mass of NbC, milled for 20 hours, exhibited the highest microhardness, with 189.7 HV on the surface and 178.4 HV in the cross-section, surpassing the values of the other composites. The electrical conductivity of the composites obtained decreases mainly with the increase in the addition of carbides.