Evaluación de la cinética de crecimiento de las capas boruradas formadas sobre la superficie de un acero AISI 4150 endurecido a través del proceso borurización base polvo

En el presente estudio se evalúa la cinética de difusión del boro en un acero AISI 4150 durante el proceso de borurización base polvo. Esta técnica de endurecimiento superficial produce en el material la formación de una fase característica, Fe2B. The morphology of Fe2B layers was observed by Optical Microscopy. Metallographic studies showed that the boride layer has a saw-tooth morphology in all the samples. The layer thickness measurements were done with the help of MSQ PLUS software. The Fe2B phase was identified by X-ray diffraction method. Finally, the mathematical model was validated.

Effect of Carbon on the Physical and Structural Properties of Boride Fe2B

For Fe-В and Fe-В-С system alloys one of the structure constituent is iron boride Fe2B but in the literature there is no information on carbon solubility limit in iron boride Fe2В. The object of this paper is to reveal the effect of carbon on the physical and structural properties of boride Fe2В. Investigation was performed for the specimens with carbon content of 0,05 - 0,80 % (wt.) and boron content of 9,0 - 15,0 % (wt.), the rest is iron. To determine the physical properties of alloys we use microstructure analysis, X-ray microanalysis and X-ray structural analysis. It is found that carbon doping of boride Fe2В leads to a feeble lattice strain and effects on the physical characteristics of boride. We estimate the free energy of boride Fe2B and carbon content in Fe2B phase. Carbon can substitute up to 3 – 8 % of boron atoms in Fe2B phase depending on the temperature which is verified by experimental data. The carbon solubility in this phase is also examined.

Corrosion Resistance of Fe-B Alloys Immersed in Molten Zinc Bath

Fe-B alloys with different boron contents were dipped into a pure molten zinc bath to investigate their anti-corrosion property. Scanning electron microscope (SEM) and energy dispersive spectrum(EDS) were used to detect the corrosion products. It is found that the corrosion mechanism of α phase is corrosion and dissolution ,while the Fe2B phase is crack mechanism because of its brittleness and excellent corrosion resistance.The Fe2B phase in eutectic structure can protect the matrix from molten zinc and restrict the reaction of Fe-Zn. With the increase of boron content, the corrosion resistance performance of the alloys improves gradually.

Improved Wear Resistance of Dendrite Composite Eutectic Fe-B Alloy

The dry-sliding tribological properties of the dendrite composite eutectic Fe-B alloys (Fe94.3B5.7, Fe75B25 Fe67B33) were studied comparatively with various sliding speeds. The friction coefficient of the Fe-B alloy changes slightly with the boron content. The wear rate of the Fe94.3B5.7 alloy with about 30 vol. % dendrite t-Fe2B is only one third of Fe75B25 alloy with 15 vol. % dendrite and Fe67B33 alloy with 90 vol. % dendrite in the high sliding speed. First, a hard t-Fe2B phase reduced the wear of the Fe-B alloy directly. Second, the compactly oxide layers resulting from oxidation of the α-Fe on the worn surfaces also decreases the wear rate of Fe-B alloys. On the whole, the wear rate of the Fe94.3B5.7 is lower than Fe67B33 and Fe75B25.

Preparation Technology of the Low Carbon High Boron Fe-C-B Wear Resistance Steel

The solidified microstructure and the modified treatment have been systematic studied for the low carbon high boron Fe-C-B steel. The cast solidified microstructures of the low carbon high boron steel are consisted of the matrix and the boride phases. The matrix phase is consisted of the ferrite, pearlite and a few martensite phases. The boride phases of the hypoeutectic steel are based mainly on the Fe2B phase. With the increasing of the boron content, the Fe2B phase is decreased. When the boron content is excess 2.6wt.%, the boride phases are changed from the single Fe2B phase to the compound structures. Meanwell, the morphologies of the boride phases are transformed from the long strip-shaped and the fish-bone reticular structure to the rosette type. The boride phases of the eutectic steel are mainly the M2B phase. However, for the hypereutectic steel, it are composed of the M23(C, B)6 and B0.7Fe3C0.3 phases. The suitable modifier for the hypoeutectic low carbon high boron steel is the compound modifier 0.2%RE+0.2%Ti. After modified, the reticular boride phases are disconnected. Moreover, there existed some of isolated massive borides. The appropriate modifier for the hypereutectic steel is the compound modifier 0.9%Nb+0.4%RE. After modified, the primary borides are fine refined and tend to round.