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In order to investigate the effect of Si content on the microstructures and properties of directionally solidified (DS) Fe-B alloy, a scanning electron microscope (SEM) with an energy dispersive spectrum (EDS), and X-ray diffraction have been employed to investigate the as-cast microstructures of DS Fe-B alloy. The results show that Si can strongly refine the columnar microstructures of the DS Fe-B alloy, and the columnar grain thickness of the oriented Fe2B is reduced with the increase of Si addition. In addition, Si is mainly distributed in the ferrite matrix, almost does not dissolve in boride, and seems to segregate in the center of the columnar ferrite to cause a strong solid solution strengthening and refinement effect on the matrix, thus raising the microhardness of the matrix and bulk hardness of the DS Fe-B alloy. [ABSTRACT FROM AUTHOR]

The effects of chromium content on microstructure, hardness and wear resistance of as-cast Fe-xCr-1.0B (x = 0, 4, 8, 12, 16, 20) alloys were investigated by means of optical microscope (OM), scanning electron microscope (SEM), x-ray diffractometer (XRD), hardness tester and ring block wear tester. The results showed that the microstructures of chromium-free alloy were mainly composed of pearlite, ferrite, and eutectic borocarbides, and the hardness was very low, only 18.8 HRC. With the increase in chromium content, the matrix of as-cast Fe-Cr-B alloy gradually began to transform from pearlite and ferrite to lath martensite, and the type of borocarbides changed from Fe2(B, C) to M2(B, C), M7(C, B)3 and M23(C, B)6 (M = Fe, Cr). When the chromium content was 12 wt.%, the hardness of alloy reached the highest value of 61.1 HRC, and the wear resistance of alloy was the best. The results of worn surface analysis showed that the wear failure of as-cast Fe-Cr-B alloy was mainly caused by multiple plastic deformation and micro-cutting. [ABSTRACT FROM AUTHOR]

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]

The effects of orientation and lamellar spacing on the interface microstructure and corrosion behavior of a directionally solidified (DS) Fe-B alloy in a hot-dip galvanization bath were investigated. The results indicated that the microstructure of the DS Fe-B alloy consisted of oriented α -Fe and Fe 2 B grains. The oriented Fe 2 B with [002] preferred growth orientation displayed low-angle grain boundaries on the Fe 2 B (001) basal plane. The DS Fe-B alloy with Fe 2 B vertical to the corrosion interface possessed the best corrosion resistance to liquid zinc owing to the formation of an interface-pinning multilayer induced by the Fe 2 B orientation. The epitaxially grown columnar ζ-FeZn 13 products were controlled by the geometric constraint of Fe 2 B grain orientation and size, and a mechanism model that explains the interfacial orientation-pinning behavior is discussed in detail. Transmission electron microscopy (TEM) results revealed that the possible orientation relationships of the oriented Fe 2 B and columnar ζ-FeZn 13 products are (001) Fe2B //(−402) ζ-FeZn13 and [002] Fe2B //[110] ζ-FeZn13 . The corrosion damage of the DS Fe-B alloy with Fe 2 B [002] orientation vertical to the corrosion interface in liquid zinc was governed by the competitive mechanisms of Fe 2 B/FeB transformation and microcrack-spallation resistance, which is proposed as being the result of a multiphase synergistic effect in the micro-structures. [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]

Highlights: [•] The as-received microstructure of bulk Fe2B comprises iron and silicon borides. [•] The orientation of Fe2B in liquid zinc strongly affects on corrosion resistance. [•] The Fe2B/FeB phase transition process of bulk Fe2B in liquid zinc occurs. [•] Phase transition and spalling dominate corrosion of Fe2B in liquid zinc. [Copyright &y& Elsevier]

The microstructures of Fe-B alloys containing different carbon and boron concentrations have been investigated. The solidification microstructures of Fe-B alloy consist of the eutectic boride, pearlite, and ferrite. Borides precipitate along the grain boundary during the formation of eutectic. After heat treatment, the phases in Fe-B alloy are composed of the boride and martensite. With increase of carbon and boron concentrations, the Rockwell hardness of Fe-B alloy becomes larger. Meanwhile, by using a pin-on-disk abrasion tester, the effects of carbon and boron concentrations on the wear behaviors including ploughing depth, roughness, and wear weight loss under different loads have been studied. The results show that the wear resistance of Fe-B alloy with higher carbon and boron concentrations is comparable with the high chromium white cast iron. [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]

The effect of Si and prolonged time on interfaces and cavitation erosion behavior of directionally solidified (DS) Fe-B alloy in flowing liquid zinc was investigated. The results show Si enriches in α -Fe intragranular and α /Fe 2 B boundaries to refine textured grains. DS Fe-B alloy with 2.5 wt%Si exhibits the best cavitation erosion resistance to flowing zinc, which is attributed to formation of alternating distributed Γ -Fe 3 Zn 10 and FeSi and subsequently columnar ζ -FeZn 13. Cavitation erosion resistance mechanism of DS Fe-B alloy with 2.5 wt%Si is manifested that Si-induced Γ -Fe 3 Zn 10 and FeSi and the rooting-whisker ζ -FeZn 13 layer can inhibit spallation and cracks of Fe 2 B and products. • DS Fe-B alloy with 2.5 wt%Si in large high-velocity flowing liquid zinc exhibits the best cavitation erosion resistance owing to unique interfacial product films. • Si segregation promotes the formation of innermost alternating distributed Γ -Fe 3 Zn 10 and FeSi and the subsequent orderly arranged columnar ζ -FeZn 13 layer in flowing liquid zinc. • There exists a possible orientation relationship of (14−1) Fe3Zn10 // (13−2) FeSi at innermost interfaces of DS Fe-B alloys containing Si in flwoing liquid zinc. • Cavitation erosion resistance of DS Fe-B alloys depends on synergies of FeSi/Γ and ζ -FeZn 13 layer to inhibit the spallation of oriented Fe 2 B and product films at interfaces. [ABSTRACT FROM AUTHOR]

Abstract: Fe3Al–20wt.%Al2O3 ultrafine grained composites with 4wt.% Cr were prepared by mechanical alloying inducing self propagating high temperature synthesis with subsequent plasma activated sintering. Microstructures of the composites were studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectrum and transmission electron microscope. Then the relative density, room temperature hardness, static corrosion resistance and dry sliding wear behavior at a temperature range of 25°C–800°C of the sintered samples were tested and analyzed. The results showed that the composites had high hardness and a good microstructure with fine grain size, high relative density. The composites with 4wt.% Cr amount also exhibited excellent comprehensive tribological properties at medium–high temperatures especially at a temperature above 500°C, although the wear resistance did not be improved at 25°C–500°C. 4wt.% Cr element addition improved the corrosion resistance of the composites significantly with the corrosion loss decreasing by 19.48%. [Copyright &y& Elsevier]

• Temperature effect on oxidation resistance of a Fe-Cr-B-Al-C-Mn-Si alloy is studied. • The oxidation resistance is best at 900 °C; it decreases with rising temperature. • The formation mechanism of oxide scale with bilayer/monolayer structure was discussed. • MnCr 2 O 4 oxides promote protective α-Al 2 O 3 oxide formation. • Selective oxidation of Al suppresses outward diffusion of Cr and Mn. The effect of temperature on the oxidation resistance of a novel wear-resistant Fe-10Cr-1.5B-6Al-0.3C-0.8Mn-0.6Si alloy is investigated. The mass growth rate shows that this alloy exhibits superior oxidation resistance at 900 °C. As the oxidation temperature increases from 900 °C to 1100 °C, the structure of the observed oxide scales transforms from a porous bilayer to a flat monolayer, while the oxidation rate increases sharply. The selective oxidation of Al suppresses the outward diffusion of Cr and Mn to form MnCr 2 O 4 oxides in the monolayer oxide scale, thereby decreasing the oxidation resistance at 1100 °C. [ABSTRACT FROM AUTHOR]