The Influence of the Third Element on Nano-Mechanical Properties of Iron Borides FeB and FeB Formed in Fe-B-X (X = C, Cr, Mn, V, W, Mn + V) Alloys.

In this study, the influence of alloying elements on the mechanical properties of iron borides FeB and FeB formed in Fe-B-X (X = C, Cr, Mn, V, W, Mn + V) alloys were evaluated using instrumented indentation measurement. The microstructural characterization of the alloys was performed by means of X-ray diffraction and scanning electron microscope equipped with an energy dispersive X-ray analyzer. The fraction of the phases present in the alloys was determined either by the lever rule or by image analysis. The hardest and stiffest FeB formed in Fe-B-X (X = C, Cr, Mn) alloys was observed in the Fe-B-Cr alloys, where indentation hardness of H = 26.9 ± 1.4 GPa and indentation modulus of E = 486 ± 22 GPa were determined. The highest hardness of FeB was determined in the presence of tungsten as an alloying element, H = 20.8 ± 0.9 GPa. The lowest indentation hardness is measured in manganese alloyed FeB and FeB. In both FeB and FeB, an indentation size effect was observed, showing a decrease of hardness with increasing indentation depth.