A Comparative Study on Boride Layer Morphology of Fe-4Co, Fe-4V and Fe-4W Binary Alloys

Abstract

In this study, the pack boronizing behavior of Fe-4M alloys (at.% M W, V, Co) along with pure iron was investigated. The boronizing process was carried out at 1100 degrees C for 3 h. The morphology, microstructure, boride layer thickness and surface properties of the formed boride layers were characterized by XRD, SEM-EDS and profilometry. The average boride layer thicknesses were 85 mu m, 130 mu m, 275 mu m and 280 mu m for Fe-4W, Fe-4V, Fe-4Co binary alloys and pure Fe, respectively. The surface roughness was not changed with the addition of alloying element into the substrate. FeB and Fe2B phases exist on all boronized samples, but their ratio changes owing to alloying elements in the substrate. The saw-tooth morphology has transformed to a smoother boride layer with the addition of alloying elements of W and V, though Co addition was ineffective on saw tooth morphology. In addition, a transition zone under the boride layer was observed for the boronized Fe-W and Fe-V alloys. The formation of precipitates of boride of alloying elements was evident in the boride layer and in the transition zone for bonded Fe-4V and Fe-4W alloys. Co has made a solid solution with iron in boride by replacing iron in the boride lattice.