The effect of vanadium on the boronizing properties of pure iron

In this study, binary Fe–V alloys with 0.5, 1, 2, 4, 8, 12, and 16 at.% V were prepared by arc melting technique and then boronized together with pure iron by the pack boronizing method at 1100 °C for 3 h. The characterization of the borided samples was carried out by SEM, SEM–EDS, EPMA, XRD, Vickers microhardness measurement and profilometry. The boride layer was mainly composed of FeB + Fe2B with a saw-tooth morphology for borided pure iron. The addition of vanadium decreased the main boride layer thickness while relative FeB thickness increased. The saw-tooth morphology changed to a smoother interface with the addition and increase of V to the substrate. Irregularly shaped V5B6 precipitates containing some Fe were formed with a similar chemical composition both in the main boride layer and in the transition zone. The precipitates in the transition zone were relatively coarser than the precipitates in the main boride layer. The volume and size of the precipitates increased with increasing V element for the Fe–V binary alloys. The individual microhardness of these precipitates was approximately 3000 HV while the microhardness of the main boride layers was 1761 HV for pure iron and between 1724 and 2445 HV for Fe–V binary alloys. The surface roughness did not change significantly with the increase of vanadium in the substrate.

► Vanadium decreases the boride layer thickness.
► Saw tooth morphology changes to flat interface with V addition.
► V5B6 precipitates formed in boride layer and in transition zone with increase of V.