Microstructural evolution and mechanical properties of TiC-containing WC-based cemented carbides prepared by pressureless melt infiltration

Abstract

WC-based cemented carbides with different amounts of TiC (0.9, 1.2, 1.5, 1.8 and 2.1 wt%) were synthesized by pressureless melt infiltration at 1200 °C for 90 min in vacuum furnace using Cu–10Ni–5Mn–3Sn binder alloy and cast WC, Ni and TiC powders. The microstructural evolution, new phase formation, and related mechanical properties of melt infiltrated alloys were investigated. Results revealed that partially-cast WC and TiC decomposed and formed Ni2W4C, W, (Ti,W)C1-x and annular-structured solid solution when the content of TiC was in the range of 1.2–2.1 wt%, whereas Ni2W4C and W were not observed in the alloy with 0.9 wt% TiC. Annular-structured solid solution was characterized by high carbon with relatively small amounts of W and/or Ti. An increase in TiC content promoted the formation and growth of Ni2W4C and (Ti,W)C1-x phases. However, the annular structure with a continuous network developed into discontinuous net-like distribution and gradually disappeared. Addition of an appropriate amount of TiC improved the Rockwell hardness (HRA) and transverse rupture strength (TRS); however, the impact toughness always decreased with the addition of more amount of TiC. The alloys with 1.8 wt% TiC, 1.5 wt% TiC, and 0.9 wt% TiC exhibited the best mechanical properties with Rockwell hardness of 93.6 HRA, TRS of 1823.4 MPa, and impact toughness of 6.33 J cm−2, respectively.