WC–Co cemented carbides are one of the most widely used materials for the production of cutting tools, for their exceptional mechanical properties. Due to the extreme mechanical and thermal conditions of the cutting operations, understanding and controlling the evolution of the microstructure of WC–Co is essential. In this paper, we study a WC-10wt.%Co. In the Co phase, a specific transition occurs around 920 K, between a low temperature brittle state, and a high temperature more ductile structure. This transition has the features of a strain glass transition. In this study, we use an inverted pendulum used for Mechanical Spectroscopy to determine the thermal activation and to prove the broken ergodicity of the transition. The observations on the broken ergodicity are confirmed and developed further by studying samples where it is possible to reduce the Internal Friction peak associated with the strain glass transition.