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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.

Influences of the tempering temperature on the microstructure, mechanical property and wear resistance of High-Boron High Speed Steel (HBHSS) roll materials were investigated by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, hardness measurement, impact tester, tensile tester and pin abrasion tester. The results show that the as-cast structure of HBHSS consists of a great amount of martensite and M2(B,C) and a few retained austenites and M23(B,C)6. After solution treated at 1,050 °C and followed by oil cooling, the amount of M23(B,C)6 carbo-borides in quenched HBHSS increases obviously and the macrohardness of the quenched HBHSS is 66 HRC, which is very close to the 65.8 HRC of as-cast HBHSS. On the whole, the hardness of HBHSS alloy shows a trend of slight decrease with increasing tempering temperature when tempered below 500 °C. While when above 500 °C, the hardness increases slightly as the tempering temperature increases and reaches a peak at 525 °C and then decreases obviously. The impact toughness of HBHSS has a tendency to increase as the tempering temperature increases. Tempering can improve the tensile strength and elongation of HBHSS, but a higher tempering temperature causes a slight decrease in both tensile strength and elongation. Excellent wear resistance can be obtained by tempering at 500 to 550 °C.

The critical points and time-temperature-transformation (TTT) curves of the isothermal transformation diagrams for a high-speed steel casting on a horizontal centrifugal casting machine had been determined experimentally in the study. The effects of quenching temperature on the microstructures and properties of centrifugal casting high speed steel (HSS) roll has been investigated using scanning electron microscopy (SEM), light optical microscopy (LOM) and X-ray diffraction (XRD) as well as using tensile, impact, and hardness tests. The results show that the HSS roll has excellent hardenability and its matrix structure can be transformed into the martensite after being quenched in the sodium silicate solution. The retained austenite in the quenching structure increases and the hardness decreases when the quenching temperature exceeds 1,040℃. The tensile strength and impact toughness of HSS roll increase once the quenching temperature is raised from 980℃ to 1,040℃. However, the tensile strength and impact toughness have no signifi cant change when the quenching temperature exceeds 1,040℃. The HSS roll quenched at 1,040℃ exhibits excellent comprehensive mechanical properties.

Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance, and high temperature properties. In this paper, in-situ (Ti, Nb)C particle reinforced Fe-based composite coatings were produced by laser cladding. The effects of Ti/Nb(atomic ratio) in the cladding powder on the formation mechanism and distribution characteristics of multiple particle were investigated. The results showed that when Ti/Nb > 1, Ti had a stronger ability to bond with C compared with Nb. (Ti, Nb)C multiple particles with TiC core formed in the molten pool. With the decrease of Ti/Nb, core-shell structure disappeared, the structure of particle got close to that of NbC gradually. It is found that the amount, area ratio and distribution of the reinforced particle in the coating containing Ti and Nb elements were improved, compared with these in the coating containing equal Nb element. When Ti/Nb = 1, the effects above-mentioned is most prominent, and the wear resistance of the coating is promoted obviously. [ABSTRACT FROM AUTHOR]

• The H13 steel block were prepared by wire arc additive manufacturing. • The microstructure was studied in detail. • The tensile strength and elongation were studied. • The internal information related to micropores is studied. • The reason of the low elongation of printing block is deduced. The H13 steel block was successfully prepared by cold metal transfer(CMT) wire-arc additive manufacturing(WAAM) method. The microstructure characteristics and mechanical properties of the printed block were both studied by experiments. It was found that there were obvious difference in the microstructure and mechanical properties between the central part and overlapping parts of the printed block. It was shown from the microstructure observation that the printed block was mainly composed of martensite and residual austenite. There was an obvious primary austenite grain boundary observed in the base phase. In addition, compared with the overlapping part, the content of residual austenite in the central part was lower. It was shown that the average value of the microhardness in the central part was 596HV, while it was 534HV for the overlapping part due to the higher content of residual austenite. Tensile tests were conducted for different direction of the printed block. Micropores with a volume of 100–400 μm3 were observed in the printed block, with 90 % of the micropores in the range of 100–200 μm3 in volume. The micropores were uniformly distributed in the sample. The presence of micropores leads to the low elongation and tensile strength. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties and abrasion resistance of Fe-B alloy with 4wt%Cr-2wt%Mn-2wt%Cu addition have been systematically investigated. The results show that the microstructures mainly consist of martensite and boride (M 2 B) in the as-cast and heat treated Fe-B alloys; after heat treatment, the morphology and volume fraction of the M 2 B have little change, meanwhile the nucleation and precipitation of secondary borocarbide M 23 (C, B) 6 probably take place in an in situ manner within martensite. Moreover, the M 2 B is identified as chemical formula of Fe 2.04 Cr 0.11 Mn 0.07 (B, C) reflecting body-centred tetragonal (bct) structure, and the secondary borocarbide M 23 (B, C) 6 has the stoichiometry of Fe 18.84 Cr 2.84 Mn 0.57 (B, C) 6 with face-centred cubic (fcc) structure. After heat treatment, the matrix hardness and bulk hardness of Fe-B alloy decrease owing to the decreasing of B/C concentration of matrix caused by the precipitation of M 23 (C, B) 6 , while the fracture toughness of Fe-B alloy increases. Meanwhile, the heat treatment will decrease the wear resistance of Fe-B alloy, i.e. the wear resistance of Fe-B alloy would decrease with reduction of the matrix hardness. [ABSTRACT FROM AUTHOR]