Microstructural alterations in WC-Co work tools by metallurgical preparation methods

Hard metals are in great demand in areas that require high hardness and wear resistance. Tungsten carbide excels in this area, especially with cobalt as a binder phase [1, 2]. For microstructural characterization, choosing an applicable preparation method is the most essential step. Publications concerning WC-Co materials were published by the National Physical Laboratory in Teddington, England, notably by Prof. B. Roebuck, though the influence of preparation methods was not entirely explored. Electron backscatter diffraction (EBSD) is one of the most common characterization techniques for metallurgical investigations. We use common preparation techniques and a few others we developed to analyze and compare the resulting surface quality and their applicability for EBSD [3, 4, 5, 6]. In addition to EBSD, the sample should be compatible with X-ray diffraction (XRD) and/or transmission electron microscopy (TEM) characterization. Our criteria consider EBSD grain indexing in orientation imaging microscopy analysis (OIM) software, changes in microstructure, cobalt leaching/cobalt losses, the size of the characterization area and ease of preparation procedure. We target the distribution of cobalt phases, hexagonal close packing (HCP) and face-centered cubic (FCC) with respect to their magnetic saturation. HCP is stable at room temperature, while FCC forms at temperatures higher than 417 °C [7].