WC-Co超硬合金のブラスト処理による残留応力と強度の関係

Abstract

The feature of cemented carbide is in the high hardness and it shows little plastic deformation before fracture by external forces, and the fracture strength is generally discussed in terms of the internal defects such as voids, produced in the production process of the powder metallurgy. The voids are regarded as the initial triggering points of cracking and act as stress concentrator. The probability of existence of these voids and their shape, size and distribution should be treated in a statistical manner and the fracture strength of these defective brittle materials must be considered in statistical processes. When some significant differences are appeared in the fracture strength of the brittle materials, the causes of the differences should be searched in other factors than the defects. In this study, the differences of the fracture strengths of WC-(5.5∼15)%Co alloys owing to blasting with other sorts of the blasting media were studied from the stand-point of residual stress measurements comparing with the surface conditions. As the result of the experiments, it was made clear that the difference of the facture strength of the cemented carbides blasted with the other sorts of blasting media would be based on the difference of the residual stresses produced by the blasting and the residual stresses of compression were discussed in terms of the hardness of the blasting media.