超微粒子超硬合金の曲げ強度の計算力学に基づく予測法

Abstract

By use of a microscopic fracture model, a computational estimation method of bending strength of ultra fine-grained cemented carbides was developed on the basis of micromechanics. A macroscopic breakage of the cemented carbides was supposed to occur when a matrix crack, which generated from a defect in ultra fine-grained cemented carbides, extended unstably. In this paper, ultra fine-grained cemented carbides which contained vanadium carbide and chromium carbide were examined, and then η-phase in them was paid attention as defects. In order to evaluate the stability of the extension of the matrix crack. stress intensity factor was introduced. After the amount of the η-phase was related to the carbon content of ultra fine-grained cemented carbides under the concept of material balance, the bending strength was estimated. The estimated results were in good agreement with the experimental ones. The effects of the carbon content of carbides and the average size of η-phase on the bending strength were also examined. The results were presented in the figures and its application to material design was discussed.