Effect of high chromium content additions in iron-bonded Ti(C,N) cermets: a hardness-toughness tradeoff

The evolution of titanium carbonitride (Ti(C,N))-based cermets has seen a notable shift towards environmentally sustainable compositions, particularly through the use of green iron (Fe) binders as alternatives to traditional nickel (Ni) or cobalt (Co) binders, for applications in wear- and corrosion-resistant tooling, such as in oil and gas, chemical processing, and marine environments. A key challenge with Fe-bonded cermets is their limited wear and corrosion resistance. This study investigates the effect of varying chromium (Cr) concentrations (20, 30, and 40 binder wt%) on the microstructural evolution, phase composition, and mechanical properties of Fe-bonded Ti(C,N)-based cermets. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses reveal well-defined core-rim structures and Cr segregation, with increasing Cr content. Grain size increases from 2.03 μm to 2.75 μm, while ceramic phase contiguity rises from 0.61 to 0.80, with higher Cr content. X-ray diffraction (XRD) confirms the presence of Ti(C,N) and Cr-rich Cr7C3 carbides, contributing to enhanced hardness of up to 1608 HV through solid solution strengthening and carbide precipitation. However, fracture toughness decreases from 11.55 to 7.82 MPa·m1/2 due to increased ceramic connectivity and Cr carbide-induced brittleness. The findings of this study provide valuable insights into optimizing Cr concentration in Fe-bonded Ti(C,N)-based cermets, balancing hardness and toughness to enhance their wear and corrosion resistance. This optimization is crucial for developing durable, environmentally sustainable cermet materials suitable for demanding industrial applications.