Coprecipitation of Co and La2O3 coprecipitation on WC for tailoring the grain distribution and boundary of high-performance coarse-grained WC-10Co cemented carbide

Abstract

The development of excellent performance coarse-grained WC-Co cemented carbides has emerged as a hot topic for cutting tools, drills, molds, wear-resistant parts, etc. In this study, the WC powder was coated by Co and La2O3 simultaneously using a new coprecipitation strategy, and its beneficial effects on the densification, microstructure and mechanical properties of WC-10Co was systematically investigated. Firstly, due to the successful introduction of La2(C2O4)3 precursor, the surprising transformation of rod-like loosely CoC2O4 to regular-spherical-like dense one was observed, further inducing the dense and uniform coating of La2O3 with Co on the surface of WC after the H2 reduction treatment. The addition of La2O3 by this way was found to improve the grain uniformity of WC in the sintered cemented carbide, inhibiting the appearance of abnormally grown grains, and preventing the conversion of CoFCC to CoHCP effectively, which should be ascribed to the segregation of La2O3 on the grain boundary of WC, produced pinning effect and inhibited the dissolution and growth of WC grains. The mechanical properties of coarse-grained WC-Co cemented carbides, including hardness, strength, fracture toughness and elastic modulus were systematically investigated, validating the beneficial effects of Co and La co-precipitation apparently. In general, this study presents a new strategy for enhancing the performance of coarse-grained WC-Co cemented carbides by both powder mixing design and grain boundary tailoring.