Fracture behaviour of a new submicron grained cemented carbide (original) (raw)

In this work, the effect of increasing argon pressure applied on a post-sintering treatment from 3 MPa to 100 MPa on the mechanical properties of a newly developed ha rdmetal grade, namely, hardness, flexural strength and fracture toughness, is reported. The as-received material has been previously 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 MPa to ≈ 3000 MPa was observed, whilst hardness (HV30≈2000) and fracture toughness (≈8 MN.m-3/2) remained practically unchanged. Both microstructural and fractographic studies revealed that this is f mainly attributed to a decrease in the amount and size of microstructural defects (namely, pores 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-3.5wt% Co composites with submicron WC grains size confirming that porosity reduction results in flexural strength improvement.

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