Carbon addition effects on microstructure and small-scale hardness for Ti(C,N)-FeNi cermets

The current study investigates the influence of carbon addition on the microstructural and micromechanical properties of Ti(C,N)-FeNi cermets with different ceramic/metal phase ratios. Evaluation of small-scale hardness is conducted by using high speed nanoindentation in conjunction with statistical analysis. It allows to gather extremely large data sets (40,000 imprints per grade and condition); and thus, detailed hardness mapping at the microstructure length scale. Subsequent statistical analysis was done by considering three mechanically distinct phases: Ti(C,N) particles, the metallic binder, and one exhibiting the composite behaviour (i.e. imprints probing two-phase regions). In general, it is found that porosity amount is reduced as ceramic/metal phase ratio decreases and carbon is added. Carbon addition is also observed to rise small-scale hardness, but only for two of the defined phases: metallic binder and the composite one. Similar trends are observed regarding the influence of ceramic/metal phase ratio and carbon addition on the inverse hardness-fracture toughness correlation measured under high applied loads.This investigation was supported by the Spanish Ministerios de Economía y Competitividad MINECO through grant MAT2015-70780-C4-P. J.J. Roa acknowledges the Serra Hunter programme of the Generalitat de Catalunya.Publicad