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Abstract: A WC–Co–Cr coating was deposited by a high velocity oxy-fuel thermal spray (HVOF) onto a 1Cr18Ni9Ti stainless steel substrate to increase its cavitation erosion resistance. After the HVOF process, it was revealed that the amorphous phase, nanocrystalline grains (Co–Cr) and several kinds of carbides, including Co3W3C, Co6W6C, WC, Cr23C6, and Cr3C2 were present in the coating. The hardness of the coating was improved to be 11.3GPa, about 6 times higher than that of the stainless steel substrate, 1.8GPa. Due to the presence of those new phases in the as-sprayed coating and its higher hardness, the cavitation erosion mass loss eroded for 30h was only 64% that of the stainless steel substrate. The microstructural analysis of the coating after the cavitation erosion tests indicated that most of the corruptions took place at the interface between the un-melted or half-melted particles and the matrix (Co–Cr), the edge of the pores in the coating, and the boundary of the twin and the grain in the stainless steel 1Cr18Ni9Ti. [Copyright &y& Elsevier]

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 La 2 O 3 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 La 2 (C 2 O 4) 3 precursor, the surprising transformation of rod-like loosely CoC 2 O 4 to regular-spherical-like dense one was observed, further inducing the dense and uniform coating of La 2 O 3 with Co on the surface of WC after the H 2 reduction treatment. The addition of La 2 O 3 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 Co FCC to Co HCP effectively, which should be ascribed to the segregation of La 2 O 3 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. • A novel is adopted to achieve two-dimensional growth of CoC 2 O 4 • The pinning of La 2 O 3 at grain boundaries tailors the grain distribution of WC • The successful introduction of La 2 O 3 prevents the transformation of Co FCC to Co HCP • The enhanced performance of cemented carbides by both powder mixing design and grain boundary tailoring are obtained [ABSTRACT FROM AUTHOR]