Refined WC grain size and improved mechanical properties in a hardmetal WC-8Co processed via short-time semi-solid hot pressing

• Published in: Journal of alloys and compounds 2021-12, Vol.889, p.161560, Article 161560
• Main Authors: Ye, Yongqiang, Xia, Haoyun, Lin, Yaojun, Chen, Fei, Shen, Qiang
• Format: Article
• Language: English
• Subjects: Bend strength; Cemented carbides; Eutectic temperature; Fracture toughness; Grain growth; Grain size; Hardmetals; Hardness; Hot pressing; Liquid phase sintering; Liquid phases; Mechanical properties; Metallurgy; Semi-solid processing; Semisolids; Sintering (powder metallurgy); Tungsten carbide
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.161560

•A new approach namely short-time semi-solid hot-pressing (STSSHP) is developed.•STSSHP produces fully dense WC-Co hardmetals with minimized WC grain growth.•WC-Co hardmetals processed via STSSHP exhibit higher hardness and ductility. To minimize WC grain growth and avoid WC-WC non-metallurgical contacts in WC-Co hardmetals, we modified conventional solid-state hot pressing into short-time semi-solid hot pressing (STSSHP) for consolidation of WC-Co powders in the present study. STSSHP can produce fully dense WC-Co hardmetals free of WC-WC non-metallurgical contacts at semi-solid temperatures lower than the ideal liquid-phase sintering temperatures within several to several ten seconds, thus minimizing WC grain growth. Herein WC-8 wt%Co processed by STSSHP at 1340 ℃ (the WC-Co eutectic temperature) for only ~15 s achieved a relative density of 99.92% without WC-WC non-metallurgical contacts. Only slight WC grain growth occurred during STSSHP relative to grain sizes in powders. The STSSHP-ed WC-8 wt%Co exhibited much smaller WC grains and thus higher hardness, fracture toughness and bend strength than those in its liquid-phase sintered counterparts. STSSHP provides a novel avenue to retain fine WC grains and hence to improve both hardness and ductility of WC-Co hardmetals.