Influence of TiC and Cr3C2 additions on the mechanical properties of a (W-Ti-Cr)C-Co sintered hardmetal

Abstract

TiWCrC-Co alloys were manufactured by conventional powder metallurgy processes in a vacuum alumina furnace. The alloys were sintered at 1550 °C, and the chemical composition was changed in order to evaluate its influence on the mechanical properties of the composite. The aim of this article is to explore the partial WC to TiC substitution effect and the microstructural changes of the alloys as a function of a Co and Cr3C2 grain growth inhibitor. Eight different alloys were sintered by changing the TiC [6–8 wt%], Cr3C2 [0.5–2 wt%] and Co [6–9 wt%] contents. The hardness was measured by the Vickers (HV30) method, and the fracture toughness was calculated by the Palmqvist method. High-Stress Abrasion Resistance tests (ASTM B611) were performed for all alloys. The Co and Cr3C2 contents influenced the mean grain size of the WC phase and thus the hardness of the alloys. The wear resistance showed a high dependence on the hardness and was not notably affected by the fracture toughness. The microstructure and phases were identified by scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The Cr content did not exceed the solubility limit in the different alloys, and all TiC formed the TiWC2 phase and was homogeneously distributed, which hindered the Ostwald ripening process of the WC grains. Alloys with lower TiC and Cr3C2 contents developed the η phase that dispersed throughout the microstructure. TiC addition improved the wear resistance of the different alloys and is a good choice for manufacturing anti-wear components. Keywords: Hardmetal, Powder metallurgy, Cermets, TiWCrC-Co alloys, Anti-wear.