The Relation between Transverse-Rupture Strength and structural Defects in P30 Cemented Carbide

The transverse-rupture strength (σm) of P30 cemented carbide (WC-36%βt-8%Co;βt solid solution of WC/TiC/TaC=45/22/33) was studied in relation to structural defects acting as the fracture source.It was found that σm of as-sintered alloy was always affected by the defect of pores, being often accompanied by βt layer or βt segregation. In case of HIP-treated alloy, such defects as cobalt pools surrounded by the βt layer or attached to by the segregated βt appeared, caused by the pores above mentioned. However, in the alloy (s-alloy) prepared by using commercially available spray-dried-powder, pores accompanied by βt layer or cobalt pools having βt layer were not observed. The higher strength of s-alloy was due to this fact. It was found that σm of P30 alloy, whether it was as-sintered alloy or HIP-treated alloy, was closely related to the structural defects peculiarly formed in this alloy.