Design of Fe2B-based ductile high temperature ceramics: First-principles calculations and experimental validation

Abstract

Iron Boride (Fe2B) has significant potential to be used as a wear- and corrosion-resistant ceramic because of its high hardness, good corrosion resistance, and low cost. However, the toughness and elastic heat resistance of Fe2B can be further improved under high-temperature wear conditions. First-principles energetics and phonon calculations showed that Ti, Cr, Mn, Co, Ni, Nb, Mo, Ta, and W can dissolve in Fe2B. Among these, Cr, Mn, and Ni can form a continuous solid solution in (Fe, M)2B. Furthermore, Ti, Cr, Mn, Co, Ni, Cu, Y, Nb, Mo, Ta, and W improved the toughness of Fe2B. The results were validated by the experimental results. It was found that the experimental fracture toughness of Fe2B doped with Cr and Ni reached 4.16 and 4.27 MPa m1/2, respectively, which are higher than 3.64 MPa m1/2 of pure Fe2B. Chemical bond analyses showed that the toughness was improved owing to the stiffening of the B–B bond and the invariability of the Fe–B bond in Fe2B by doping Cr and Ni with increasing pressure. The elastic heat resistance of alloyed Fe2B was related to the degree to which the B–B and Fe–B bonds weakened with temperature. The less these bonds strength weakened with increasing temperature, the better the elastic heat resistance. The bond strength of Fe–B and B–B bonds in Fe2B doped with Cr showed a minimum decrease with increasing temperature, whereas the bond strength of Fe–B and B–B bonds in Fe2B doped with Ta showed a maximum decrease with increasing temperature. This indicates that the alloying element Cr can improve the elastic heat resistance of Fe2B, while Ta decreases the elastic heat resistance of Fe2B.