A Consideration of Relation between Transverse Rapture Strength and Size of Fracture Origin

The relation between transvers rupture strength, σm, and defect size, 2a, on the fracture origin on ultrafine-grained WC–10Co cemented carbides sintered in vacuum and hot isostatic pressed (HIPed) with the pressure of 1 and 100 MPa were investigated. The values of σm and 2a were obtained broadly by measuring for a lot of specimens as sintered and HIPed states. A clear correlation was provided on relations between σm and 2a on two type plots of σm vs (2a)-1/2 and σm-1 vs (2a)1/2 and the relations were affected by WC grain size of the cemented carbides. Limiting strength on the plots of σm vs (2a)-1/2 were confirmed clearly. The limiting strength seemed to be affected by not only mean WC grain size of specimen but also carbon content. It is suggested that limiting strength is affected by matrix strength.