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The microstructure and mechanical properties of three kinds of low-carbon medium-manganese steels with different Si contents under an intercritical heat treatment process were studied. The results show that the microstructure of the test forged steel is mainly composed of ferrite and pearlite. After 900 °C complete austenitizing quenching + 720 °C intercritical quenching, the microstructure of the test steel is mainly composed of ferrite and martensite. With the increase in Si content, the microstructure becomes finer and more uniform. The microstructure of the test steel after 900 °C complete austenitizing quenching + 720 °C intercritical quenching + 680 °C intercritical tempering is dominated by ferrite and tempered martensite, with a small amount of retained austenite and cementite. As the Si content increases, the boundaries between ferrite and tempered martensite become more clear. The tensile strength and hardness of the test steel increase with the increase in Si content, while the elongation first increases and then decreases; the comprehensive performance of the test steel is the best when the Si content is 0.685 wt. %, with a tensile strength of 726 MPa, a yield ratio of only 0.65, the highest elongation of 30.5%, and the highest strong plastic product of 22,143 MPa.%. [ABSTRACT FROM AUTHOR]

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 ?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 oC, 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 oC and tempered from 200 oC has excellent combined properties; its hardness and impact toughness are 61.5 HRC and 8.8 J.m-2 respectively.

Hypereutectic High Chromium Cast Iron (HHCCI) is a new type of corrosion-wear-resistant material developed from ordinary high chromium cast iron by increasing the chromium and carbon content and is often used in abrasive environments where wear and corrosion interact. The corrosion wear resistance of the HHCCI is related to the number, size, shape and distribution of carbides and the microstructure of the matrix. This paper reviews the research progress in improving the corrosion wear resistance of HHCCI from various aspects such as primary carbide refinement, heat treatment, deep cooling treatment and alloying, etc. Among the methods of refining primary carbides are modification, semi-solid treatment and current pulse treatment. In addition, we also analyze the potential of Cr, V, Nb, Mo, Mn, W, Ni, Cu, Si, N and other alloying elements to improve the corrosion wear resistance of HHCCI. The mechanism for improving the corrosion wear resistance of HHCCI is also explored in depth and research contents worthy of attention are proposed to further improve the corrosion wear resistance of HHCCI. In the future, the author believes that modification + alloying + heat treatment is the most potential application method to improve the corrosion wear resistance of HHCCI. The corrosion wear resistance of HHCCI can be further improved by refining the primary carbide (such as adding rare earth, Ti and other modified elements) + heat treatment (with cryogenic treatment) to improve the strength + alloying (such as adding low-cost, high-potential alloy elements such as N and Si) to improve the corrosion wear resistance of the matrix. [ABSTRACT FROM AUTHOR]

Carbidic austempered ductile iron (CADI) is a new type of wear-resistant material with high performance developed in recent years. The effect of austempered temperature on the microstructure and properties of high B-bearing CADI was investigated. Boron is an element that significantly interferes with the spheroidization process. When the boron content in CADI is high, the crystallization of spheroidal graphite in the as-cast microstructure is hindered, and its roundness, spheroidization rate, and volume fraction are significantly reduced. The results of its heat treatment process show that with the increase of austempered temperature, the volume fraction of residual austenite in the matrix increased, the size of acicular ferrite becomes coarser, and the ferrite also increases significantly, and the macroscopic hardness and wear resistance of the specimens gradually decreased. [ABSTRACT FROM AUTHOR]

Abstract: The effect of heat treatment on the performances of multi-element low alloy wear-resistant steel (MLAWS), which is used to make the rolling mill torii liner, was investigated. The results show that the hardness and tensile strength increase as the quenching temperature is increased from 840 to 900°C. However, the hardness decreases rapidly as the quenching temperature is increased beyond 900°C, while the temperature has little influence on the tensile strength when it exceeds 900°C. No clear influence on the impact toughness has been observed unless the quenching temperature is beyond 920°C. As the tempering temperature exceeds 300°C, tiny ɛ carbides separate out from martensite and bainite complex structures and cause the carbon content in the complex structures to decrease. This results in the toughness to increase significantly. The best wear resistance can be obtained by tempering at 350°C. The optimum heat treatment of MLAWS comprises quenching at 900–920°C and tempering at 350–370°C. [Copyright &y& Elsevier]

The microstructure and age-hardening behavior of a new kind of Al-modified low carbon high boron high-speed steel (BHSS) were investigated. The results show that the as-cast microstructure of BHSS mainly consists of M 2 B borides and dendrite martensite. Al addition can promote the formation of pearlite and ferrite. After heat treatment, proper Al addition can not only remarkably increase the bulk hardness of BHSS during destabilized condition, but also promote the subsequent precipitation-hardening effect. The tempered BHSS with 0.6 wt%Al exhibits the best precipitation-hardening behavior at 520 °C tempering, which is attributed to the presence of some dispersive M 23 (B,C) 6 and M 6 (B,C) secondary precipitations. The proper Al can promote the formation of M 7 (B,C) 3 and inhibit the coalescence of secondary precipitations. TEM analysis indicates that there exists an orientation relationship of (112) M23(B,C)6 //(112) M6(B,C) in the steels. [ABSTRACT FROM AUTHOR]

Abstract: The effect of heat treatment temperature on the microstructure and mechanical properties of a Fe–4.0C–18.0Cr–1.0Mo–1.0Ti (wt.%) hypereutectic high chromium white cast iron was investigated. The response of the alloy to heat treatment and, therefore, the microstructures developed, differed significantly. With the increase of the heat treatment temperature, the precipitated secondary carbides changed from M3C to M7C3 and the retained austenite content increased. With the increase of the heat treatment temperature, the bulk hardness and matrix microhardness both increased and reached peak values of 64.6HRC and 850HV, respectively at the temperature of 1000°C. But they all decreased at the heat treatment temperature of 1050°C. The impact toughness of the alloy increased significantly compared with the conventional cast hypereutectic high chromium white iron (containing 4.0wt.% C and 17.0wt.% Cr) without titanium and inoculation and its value was in the range of 6.1–6.9J/cm2, but it did not change very much with the increase of heat treatment temperature. [Copyright &y& Elsevier]

In this paper, the effect of heat treatment (760–1060 °C) on tribological behavior of selective laser melted Ti6Al4V alloy against Si 3 N 4 counter-ball under different applied loads was investigated. Results show the wear rate of as-built Ti6Al4V alloy increased firstly and then gradually decreased with increasing the heat-treatment temperature, which obtained the lowest value when the heat treatment temperature was 1060 °C, exhibiting the best wear resistance. The higher applied load led to larger wear rate and lower coefficient of friction. The wear mechanism was strongly dependent on the microstructure transformation, micro-hardness and applied load, which was discussed in detail. • Ti–6Al–4V alloys were fabricated by selective laser melting. • Friction coefficient and wear resistance were optimized by heat treatment. • Higher applied load led to larger wear rate and lower friction coefficient. • Wear mechanism was strongly dependent on the microstructure transformation, micro-hardness and applied load. [ABSTRACT FROM AUTHOR]