Search

The effects of silicon alloying and heat treatment on the microstructure and properties of Fe-35Cr-4C-xSi (x = 0.5, 1.2, 19, 2.6) hypereutectic high-chromium cast iron (HHCCI) were explored through first-principles calculations and phase diagram calculations combined with XRD, SEM, TEM and other methods. With the increase of Si content, the matrix structure of HHCCI transforms from martensite to ferrite. The phase diagram analysis reveals that higher silicon content results in elevated austenite transformation initiation temperatures, reduced austenite phase areas, and expanded ferrite phase regions. Additionally, the study calculates the diffusion activation energy of C atoms within silicon-bearing and silicon-free HHCCI matrices, providing valuable insights into the role of silicon in promoting the transformation of the HHCCI matrix into ferrite. Notably, silicon facilitates the diffusion of C atoms into the silicon-bearing HHCCI matrix, thereby preventing complete austenitization. After ultra-high-temperature heat treatment, the matrix structure of high-silicon HHCCI (1.9 wt.% Si) can be transformed from ferrite to martensite. With the increase of Si content, the corrosive wear resistance of HHCCI increases first and then decreases. The 1.9Si HHCCI after ultra-high-temperature heat treatment exhibits the best corrosive wear resistance in both acidic and alkaline corrosive wear environments, and the silicon-bearing HHCCI is more resistant to alkaline corrosive wear. This study reveals promising applications of silicon-bearing HHCCI in industries such as hydraulics and coal mining, particularly as a material for making slurry pumps. Notably, in comparison with previous work by our research group, this study delves deeper into the mechanisms underlying the structural and performance changes of silicon-bearing HHCCI due to heat treatment and silicon content variation. [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]