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The microstructure and oxidation kinetics of Fe-B-based alloys at 927 K in air with different boron concentrations of 0.95, 1.45, 2.10, and 3.08 wt% were studied. The alloy microstructures were interpreted to consist of α-Fe, FeB, and pearlite. After 100-h oxidation, the oxides comprised FeO at the surfaces and a mixed BO-SiO layer at matrix/oxide interface. The formation of mixed oxides layer was affected by boron content in the alloy and had obvious influence on the oxide morphology. The isothermal oxidation kinetics at 973 K exhibited initial rapid mass loss followed by slow mass loss, and the oxidation rate constants of the two oxidation stages demonstrated completely opposite tendencies with the increase of boron. The Fe-B 3.08 wt% alloy exhibited the best oxidation resistance after 100 h of cyclic oxidation due to the formation of a well-distributed and continuous BO-SiO mixed oxide layer. [ABSTRACT FROM AUTHOR]

In the present study, the microstructure and mechanical properties of cast Fe-10Cr-1.5B (FCB) alloy after different heat treatments were studied. The results showed that the as-cast microstructure of FCB alloy consists of a-Fe, M(M=Cr, Fe, Mn)2(B, C) and M(M=Cr, Fe, Mn)7(C, B)3 type borocarbides, and small amounts of pearlite and austenite. After oil quenching treatment, metal matrix transformed into the martensite from the mixture of martensite, pearlite and austenite. There are many M(M=Cr,Fe,Mn)23(C,B)6 type borocarbide precipitates in the metal matrix, and eutectic borocarbide appears with an apparent disconnection and isolated phenomenon. When the quenching temperature reaches 1,050 °C, the hardness of FCB alloy is the highest, but the change of quenching temperature has no obvious effect on impact toughness of FCB alloy. After tempering, the eutectic microstructure of FCB alloy appears with a "two links" trend. With the increase of tempering temperature, the hardness of FCB alloy decreases gradually and impact toughness increases gradually. Cast FCB alloy oil-quenched from 1,050 °C and tempered from 200 °C has excellent combined properties; its hardness and impact toughness are 61.5 HRC and 8.8 J•cm-2 respectively. [ABSTRACT FROM AUTHOR]