WC-10%Co超硬合金の抗折力の温度依存性

Abstract

The transverse-rupture strength of WC-10%Co cemented carbide was studied in the temperature range from room temperature to 900°C, paying attention to the structural defects or some defects which would act as a fracture source. The WC-10%Co alloy of medium carbon content with a mean carbide grain-size of about 1.2 μ was vacuum-sintered and used as specimens. The transverse-rupture strength test was carried out according to the Japanese Industrial Standard.The results obtained were as follows: (1) Below about 600°C, common structural defects such as pores or coarse WC grains were confirmed to act as fracture sources; however, at higher temperatures above about 600∼700°C, they did not tend to act as fracture sources. At still higher temperatures, a small region with irregularly rugged appearance, i.e., a region of stable crack propagation, was formed due to increased plasticity of the alloy. It was found that the region did not act as a fracture source. (2) The strength of the sound matrix having none of the defects gradually decreased with rising temperatures up to about 600°C; it sharply did above about 600∼700°C and above about 800°C it agreed with the transverse-rupture strength of the alloy. (3) The sharp changes at about 600∼700°C in the fracture mode which are closely related to the change in the sort of fracture source and strength of the alloy, etc., would be related to the strain-induced transformation of the binder phase.