Mechanisms for the degradation of strength and wear-resistance of WC based cemented carbides due to faster cooling

•Free carbon at the carbide–binder interface decreases the strength.•Free carbon at the carbide–binder interface decreases the wear-resistance.•Mechanisms are related to the microcracking along the carbide–binder interface.•Microcracking along the carbide–binder interface facilitates the macrocracking.•Free carbon at the carbide–binder interface causes the “reptile skin” wear.

Faster cooling after sintering or the heat-treatment like brazing and high temperature joining can cause the formation of the layers of free carbon at the carbide–binder interface of the WC based cemented carbides. Formation of the free carbon layers at the carbide–binder interface decreases the transverse rupture strength by up to 10–15%, dramatically decreases the wear-resistance, but does not affect the hardness of the cemented carbide. This paper concentrates on the possible mechanisms of the reduction of the transverse rupture strength and the degradation of the wear-resistance of cemented carbides when the free carbon layers are formed due to the faster cooling. The microcracking along the carbide–binder interfaces that are weakened by the presence of the brittle free carbon layers plays the role of the additional defects for the strength and facilitates the initiation and growth of the macrocracks that can form the “reptile skin” pattern on the wear surface that is associated with the dramatic decrease of the wear-resistance of cemented carbides.