Microestrutura e propriedades dos compósitos WC-10%CrMnFeCoNi preparados por moagem de alta energia e sinterização SPS

Abstract

Metal alloys traditionally have one main matrix, with additions of secondary elements to improve their properties. However, high entropy alloys (HAE) challenge this paradigm by using multiple main elements, creating a simple solid solution, which results in excellent characteristics and properties. Research has explored the potential of high entropy alloys as substitutes for the cobalt (Co) ligand in tungsten carbide (WC) carbide. With this in mind, the aim of this work was to study the high entropy alloy (CrMnFeCoNi) and its use as a substitute for the conventional binder in hard metal obtained by high-energy milling (HEM) and sintering via SPS. The analyses were carried out using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD). The mechanical properties were assessed using Vickers hardness. HEM, carried out for 10, 20 and 30 hours, proved to be effective in forming HAE, promoting deformation, fractures and cold welding of the particles. After 30 hours of milling, the FCC phase of the alloy was predominant, with amorphization of the secondary phases. In the WC-10%CrMnFeCoNi composite, HEM influenced the morphology and size of the particles, resulting in good dispersion of the phases and high incorporation of the alloy into the WC particles, even after only 10 minutes of mixing. XRD analysis revealed the WC and HAE phases, with no indication of chemical reactions or impurities. Sintering resulted in almost uniform microstructures, with good dispersion of the WC particles in the binder matrix and low porosity. The composite with HAE milled for 30 hours showed better homogenization and dispersion of the phases, which favoured sintering and reduced porosity compared to the other samples. EDS analysis confirmed these results. The hardness values of the samples varied, with 1786.9 HV1 (10 hours), 1643 HV1 (20 hours) and 1864 HV1 (30 hours). The best result was observed for the composite produced with HAE ground for 30 hours, as it showed greater homogenization and less porosity, resulting in an increase in hardness.