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In this work, the as-cast directionally solidified (DS) Fe–B alloys with various Si contents and different boride orientation were designed and fabricated, and the as-cast microstructures and static oxidation behaviors of the DS Fe–B alloys were investigated extensively. The as-cast microstructure of the DS Fe–B alloys consists of the well-oriented Fe2B columnar grains and α-Fe, which are strongly refined by Si addition. The oxidation interface of the scales in the DS Fe–B alloy with 3.50 wt.% Si demonstrates an obvious saw-tooth shaped structure and is embedded into the alternating distributed columnar layer structures of the DS Fe–B alloy with oriented Fe2B and α-Fe matrix, which is beneficial to improve the anti-peeling performance of the oxide film compared with lower amounts of Si addition in DS Fe–B alloys with oriented Fe2B [002] orientation parallel to the oxidation direction (i.e., oxidation diffusion direction, labeled as Fe2B// sample). In the DS Fe–B alloys with oriented Fe2B [002] orientation vertical to the oxidation direction (i.e., labeled as Fe2B⊥ sample), due to the blocking and barrier effect of laminated-structure boride, Si is mainly enriched in the lower part of the oxide film to form a dense SiO2 thin layer adhered to layered boride. As a result, the internal SiO2 thin layer plays an obstructed and shielded role in oxidation of the substrate, which hinders the further internal diffusion of oxygen ions and improves the anti-oxidation performance of the Fe2B⊥ sample, making the average anti-oxidation performance better than that of the Fe2B// sample. [ABSTRACT FROM AUTHOR]

The microstructure and properties of Fe-1.50 wt%B-0.40 wt%C high-speed steel (i.e. High boron high-speed steel, HBHSS) containing various Al contents have been investigated. The results show that the microstructure of HBHSS is composed of martensite, a little M 6 (C,B) and a large number of eutectic M 2 B borides. With the increase of aluminum, the martensite can reduce and lots of ferrite and pearlite occur, while M 2 B boride is gradually refined and isolated. Meanwhile, most of aluminum is mainly segregated within the ferrite grains. The room tensile strength of the steel begins to decrease when Al content exceeds 0.6 wt%, whereas the fracture and impact toughness are remarkably enhanced. A little aluminum can maintain high-temperature tensile stress of the steel at 500 °C and simultaneously improve its elongation. The high-density dislocations can be formed within Al-segregated ferrite zone to exhibit the strengthening and toughening roles, and a possible orientation relationship between (Fe,Cr) 2 B and multi-component M 2 B is (110) (Fe,Cr)2B ∕∕ (110) M2B in the steels. [ABSTRACT FROM AUTHOR]

The effect of erosion angle on erosion behavior of the as-cast Fe-B alloy in flowing liquid zinc was investigated. The results show that the erosion rate of Fe-B alloy decreases linearly with increasing erosion angle. The erosion resistance of Fe-B alloy is better than that of 316L stainless steel, which is attributed to the favorable barrier effect of net-like FeB that resists erosion by flowing liquid zinc. Meanwhile, the ductile matrix can provide support in preventing borides from spalling and borides cause barrier effect on flowing liquid zinc during liquid zinc erosion, which shows a synergistic erosion-corrosion behavior between the matrix and borides. Moreover, an increase in erosion angle can cause a decrease in the removal effect of the flowing liquid zinc scouring component on the erosion compounds. Therefore, the quantity of erosion compounds increases at the erosion interface, weakening the mass transfer process and decreasing the erosion rate of the Fe-B alloy. [ABSTRACT FROM AUTHOR]

This study investigates the effect of cerium on the microstructures, mechanical properties of medium carbon Fe-B cast alloy. The as-cast microstructure of Fe-B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the unmodified alloy, the eutectic boride structures in the modified alloy are greatly refined. Cerium promotes the formation of CeO phase. CeO can act as effective heterogeneous nuclei of primary austenite, and refine austenite and boride. After heat treatment, the impact toughness of the modified alloy is higher than that of the unmodified alloy because there are more broken borides in the modified alloy. Meanwhile, the fracture mechanism of medium carbon Fe-B alloy is depicted and analyzed by using fractography. [ABSTRACT FROM AUTHOR]

The effect of hot forging on the microstructure and abra-sion resistance of Fe-B alloy was studied. The results showed that boride networks are broken down by hot forging. After hot forging, the hardness of Fe-B alloy increased marginally, and the toughness increased considerably. In the two-body abrasion test, unforged Fe-B alloy exhib-ited excellent wear resistance and soft abrasive tended to show higher wear resistance. When alloys were tested against very hard abrasives, the wear resistance of forged Fe-B alloy was similar to that of unforged Fe-B alloy, but in the case of soft abrasives the wear resistance of forged Fe-B alloy was lower than that of unforged Fe-B alloy. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and crystallography of eutectic borides and secondary precipitations in 18wt.% Cr–4wt.% Ni–1wt.% Mo–3.5wt.% B–0.27wt.% C steel have been investigated extensively. The results show that the as-cast microstructure of Cr–Ni–Mo-containing Fe–B steel is composed of a dendritic martensite with large interdendritic eutectic borides. Transmission electron microscopy (TEM) results confirm that the borides are indexed to Cr- and Mo-rich M2B-type borides with the chemical formulas of Fe(1.35–1.36)Cr(0.92–1.05)B0.96 and Fe0.73Cr0.45Mo0.78B, respectively. The cluster-like boride possesses a possible orientation relationship between body-centred orthorhombic Cr-rich M2B and martensite with //〈110〉α growth direction. After destabilization, M23(C, B)6 secondary borocarbide with a specific orientation relationship precipitates first and thereafter coarsens following the appearance of M7(C, B)3 precipitation with the increasing destabilization temperature at the same soaking time, thus leading to a large decrease of Cr content in the martensite. However, no M6(C, B) secondary borocarbide is found in as-destabilized Fe–B steel. Destabilization treatment has no effect on the morphology of eutectic borides. The secondary borocarbides have the stoichiometry of (Fe18.26Cr4.74)(B, C)6 and (Fe3.86Cr3.14)(B, C)3 respectively. The high-resolution TEM results indicate that the nucleation and precipitation of M23(C, B)6 occur at the grain/subgrain boundaries as well as partial within martensite, and a subsequent transformation from M23(C, B)6 to M7(C, B)3 takes place in situ, which is probably owing to the crystalline defects of dislocations and stacking faults in the structures caused by lattice distortion. [Copyright &y& Elsevier]

High boron cast steel is brittle owing to the network of boride which limits its applications. In order to improve its toughness, the high boron cast steel was treated with combined processes of plastic deformation and heat treatment as will be discussed in this article. The prepared samples were analyzed using scanning electron microscope (SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD). The results show that plastic deformation breaks up boride network and uniformly distributes broken boride particles in the matrix. During subsequent heat treatment, spheroidized borides are obtained. Compared with undeformed samples after heat treatment, the hardness of the deformed samples after heat treatment increases marginally (from 51.4 to 54.7 HRC) while the toughness increases considerably (from 5 to 107 J/cm). Fracture surface changes from brittle morphology to dimple morphology. [ABSTRACT FROM AUTHOR]

This research work studies the effects of chromium on microstructure and abrasion resistance of Fe-B cast alloy. The results show that eutectic boride changes from continuous network to less continuous and matrix changes from pearlite to martensite with the increase in chromium content in the alloy. Meanwhile, an increase in chromium addition in the alloy leads to an increase in the chromium content in MB-type boride because chromium can enter boride by substituting for iron in FeB. Under two-body wear, Fe-B cast alloy exhibits excellent wear resistance. When alloys are tested against soft abrasive, chromium can markedly improve the wear resistance of Fe-B cast alloy, whereas excessive chromium can reduce the wear resistance. The wear resistance of Fe-B cast alloy increases first and then decreases with the increase in chromium. But when tested against hard abrasive, since the hardness of SiC is much higher than that of MB boride, an increase in chromium content marginally increases the wear resistance. Weight losses of Fe-B cast alloy increase with the increase in the load and exhibit the linear relationship. [ABSTRACT FROM AUTHOR]

Abstract: The interfacial morphology and corrosion resistance of low carbon Fe–B cast steels in zinc bath at 520°C were investigated. The results show Fe–B cast steel containing high Cr and Ni exhibits the best corrosion resistance to liquid zinc. The corrosion layers are composed of Γ-Fe3Zn10, δ-FeZn10, ξ-FeZn13 and η-Zn. The corrosion behaviour of Fe–B cast steels includes the following processes: the preferential leach and dissolution of Cr and Ni, the formation of Fe–Zn compounds controlled by zinc atom diffusion, and the spalling of borides without the supporting role of α-(Fe,Cr) matrix corroded by liquid zinc. [Copyright &y& Elsevier]

The solidification microstructure, crystallography of eutectic precipitations and mechanical properties of high boron steel with various aluminium and chromium concentrations have been investigated extensively in the present study, as the foundation of the further analysis about the corrosion and abrasion properties at elevated temperature. The experiment results indicate that the as-cast microstructures of test alloys mainly consist of a dendritic matrix with many interdendritic precipitations. The Fe–B binary alloy is mainly composed of ferrite, Fe 2 B and pearlite and the Fe–B–Al ternary alloy consists of α-(Fe, Al) solid solution, Fe 2 B and Fe 3 AlC 0.5 . When aluminium and chromium elements are added synchronously, the as-cast microstructure changes to α-(Fe, Al, Cr) solid solution, (Fe, Cr) 2 B boride, M 7 (C, B) 3 and M 23 (C, B) 6 borocarbides. Moreover, the nucleation and growth of M 7 (C, B) 3 borocarbide is adhere to (Fe, Cr) 2 B boride because of an interphase match between crystal plane (10 1 ( — ) 0) of M 7 (C, B) 3 and (010) of Cr-rich (Fe, Cr) 2 B. Alloy Fe-1.46 wt. % B-0.22 wt. % C-11.92wt. % Cr-8.73 wt. % Al shows the highest impact toughness value. The main fracture mode is brittle fracture of boride and tough fracture of matrix. [ABSTRACT FROM AUTHOR]