Relaxation time shift of Cobalt related internal friction peak in WC-Co cemented carbide

Cemented carbides are widely used in the cutting tools industry for their mechanical properties. They are composite materials made of hard tungsten carbide grains jointed together by a ductile cobalt binder. Due to the extreme conditions of use of the tools, understanding the evolution of the microstructure of the two phases is essential. This evolution can be followed by Mechanical Spectroscopy, either as a function of the temperature, or of the frequency. A general overview of the spectrum reveals three mechanical loss peaks. The second peak presents a transition in its Arrhenius plot at 1140 K, when measured in isothermal frequency scans. The temperature of this transition corresponds with the Curie temperature of the cobalt in WC-Co. However, temperature scans do not reveal any shift in the Arrhenius plot. This result shows how the presence of a phase transition leads to the measurement of apparent activation energies when a relaxation peak is measured in out-of-equilibrium conditions. •The Temperature and Frequency Dependent Internal Friction spectra of a WC-Co cemented carbide are determined.•A shift of the relaxation time of one of the peaks is observed in the Arrhenius plot of the second peak at 1140 K.•This shift is correlated with the magnetic transition of the cobalt phase.•This shift can only be observed by measuring Frequency Dependent Internal Friction.