The pack-boronizing of pure vanadium under a controlled atmosphere

Pack boronizing of pure vanadium was performed at 1100 °C for 4, 8, 12 and 16 h under a controlled atmosphere. Characterization of the boride formed on the surface of pure vanadium was carried out by metallographic techniques, profilometry, SEM-EDS, XRD and microhardness measurements. The metallographic studies revealed that a single boride layer with dense, compact and relatively smooth morphology was formed on the surface of pure vanadium. The interface between boride layer and base metal was wavy in nature. The formation of only the VB2 phase on pure vanadium was confirmed by surface and cross-sectional XRD analysis. The microhardness of the boride layer was approximately 3700 HV for all boriding times. Fracture toughness of the boride layer was evaluated using Vickers indentation, giving the value of 2.1-5.9 and 1.7-3.4 MPa m1/2 for Palmqvist and median/radial approaches, respectively. Thickness of the boride layer increased almost parabolically from about 23 to 50 μm with boriding time. Surface roughness of the coating was relatively increased from approximately 0.58 to 2.25 μm by boriding duration.