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Fracture behaviour of a new submicron grained cemented carbide
Publication . Oliveira, Fernando Almeida Costa; Lopes, A. C.; Fernandes, Jorge Cruz; Sacramento, J.; Valente, M. A.
In this work, the effect of increase argon pressure applied on a post-sintering treatment from MPa to MPa on the mechanical properties of a newly developed hardmetal grade, namely hardness, flexural strength and fracture toughness, is reported. The as-received material has been prviously sintered at 1460ºC under 2 MPa argon pressure from powder mixtures of WC and 3,5 wt% Co together with minor additions of VC, graphite and a pressing lubricant. By increasing the argon pressure, a significant increase in flexural strength from ≃ 1500 MP to ≃ 3000 MPa was observed, whist hadness (HV30≃2000) and fracture toughness (≃8 MN.m⁻3/2) remained practically unchanged. Both microstructural defects (namely, pore and metallic inclusions). Furthermore, fracture has been found to occur mainly by intrinsic (bulk) defects rather than surface-related ones, suggesting that surface finishing did not affect flexural strength measurements. Hot isostatic pressing has been successfully used to consolidate WC-3,5 wt% Co composites with submicron Wc grains size confirming that porosity reduction results in flexural strength improvement.
2008Periodical Open access Show more