日本金属学会誌

J. Japan Inst. Metals, Vol. 45, No. 4 (1981),
pp. 432-437

Fracture Toughness and Bend Strength of Cemented Carbides

Etsuo Ohtsuki1, Tomohisa Kito2 and Yoshimichi Masuda1

1Department of Metal Processing, Faculty of Engineering, Tohoku University, Sendai
2Faculty of Engineering, Tohoku University, Sendai. Present address: NGK Spark Plug Co., Ltd., Nagoya

Abstract:

In order to determine the factors controlling the bend strength of sintered WC-Co alloys, the transverse rupture test and fractography have been performed on 9 kinds of alloys. By the choice of the length of the minor axis of the ellipse inscribed in the cross section of a defect, a, as the size of the fracture-initiating defect, two types of relationships were found to hold between nominal stress, σ n, acting on the defect and the defect size. When the relevant defect size was larger than a critical size, ac, the nominal stress was inversely proportional to the root of the defect size, and the gradient of σ n vs Y/ √π a was equal to fracture toughness KIC of the alloys. (Y: Geometrical factor of defect.) On the other hand, when the defect size was smaller than the critical size, the nominal stress became independent of the defect size. Fracture toughness of the alloys was found to be proportional to the cobalt content and it was considerably influenced by the carbon content.


(Received 1980/09/26)

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