PhD Thesis Defense - Verónica Collado Ciprés

This PhD thesis focuses on describing, modeling, and understanding the hot deformation behavior of cemented carbides (WC–Co hardmetals) under realistic, service-like conditions. By combining high-temperature mechanical testing with physically based constitutive modeling, this research bridges the gap between room-temperature characterization and the extreme thermomechanical demands experienced during actual industrial use.

The study centers on three interconnected areas of investigation:

• Deformation Mechanisms of the Cobalt Binder: Through hot compression testing, the research characterizes the deformation behavior of sintered cobalt, revealing that high-temperature plastic flow is governed by dislocation glide and climb, controlled by cobalt self-diffusion.

• Constitutive Modeling of the WC–Co Composite: A physically based constitutive model breaks down the total flow stress into contributions from the binder phase, the rigid WC skeleton, and phase-interaction effects. 

• Microstructural and Grain Size Effects: Integrating WC grain size into the constitutive model demonstrates that fine-grained structures offer superior resistance at moderate temperatures but soften rapidly at elevated temperatures due to grain boundary sliding. Conversely, coarser WC grains better preserve structural integrity under severe thermal stress, as confirmed by electron backscatter diffraction analysis.

Ultimately, this work establishes a generalizable, physics-based framework that links microstructural parameters directly to high-temperature performance, offering practical predictive tools for the rational design of wear-resistant hardmetals operating in extreme environments.