Achieving excellent mechanical properties and wear resistance in Fe49Mn30Co10Cr10C1 interstitial high-entropy alloy via tuning composition and stacking fault energy by Nb doping

In this study, the effects of Nb doping on the mechanical properties, deformation mechanism, and wear resistance of an Fe49Mn30Co10Cr10C1 interstitial high-entropy alloy (HEA) were studied. Adding 1 at.% Nb resulted in multi-scale NbC particles. The yield strength and elongation remained almost unchanged, and the wear rate was significantly reduced. The precipitation strengthening of nano-NbC particles offsets the decrease in interstitial strengthening. The formation of NbC particles consumed C, reduced the stacking fault energy (SFE) of the alloy, significantly enhanced the transformation-induced plasticity (TRIP) effect, and offsets the deterioration effect of micron-sized NbC particles on plasticity. After adding Nb element, the volume fraction of strain-induced martensitic transformation in the tensile fracture increases from 13.2 % to 30.6 %. The wear mechanism of the two alloys under sliding wear conditions is mainly abrasive wear. Micron-sized NbC blocks the expansion of the groove and protects the matrix. In addition, the Nb-doped high-entropy alloy produced a thicker deformation ultrafine grain layer and a strain-induced phase transition layer below the wear track. The thicker deformation layer and micron-sized NbC particles reduced the wear rate by more than 23.1 %. The rationality of the existing method for calculating the wear rate with the unit load as a parameter was analyzed, and a new method with the unit maximum shear stress as a parameter is proposed.