Micromechanical properties of WC-(W,Ti,Ta,Nb)C-Co composites

A deep knowledge of micromechanical properties of each constitutive phase of cemented carbides is crucial to improve their performance on the basis of microstructural design optimization. In the present work, a systematic experimental procedure has been followed to determine the intrinsic hardness of individual WC and (W,Ti,Ta,Nb)C particles, as well as that of the metallic binder, within a WC-Co composite containing a solid solution of mixed carbide as a third phase. In doing so, massive nanoindentation and statistical analysis of the gathered data are combined. Results showed that (W,Ti,Ta,Nb)C particles are significantly harder than WC ones, independent of the hardness anisotropy exhibited by the latter. Hardness assessment for the metallic binder required further analysis, including data deconvolution using thin film models and consideration of substrate effects. The attained hardness values are then used for estimation of effective flow stress of the metallic phase by means of Tabor's equation, yielding values ranging between 1.3 and 2.0 GPa. These high constraining-related values are finally validated by experimental assessment of stress levels at which strain bursts are identified in stress-strain curves obtained by uniaxial compression of micropillars.