STUDY ON NIOBIUM CARBIDE COATING FORMATION ON AISI L۲ STEEL USING THERMO-REACTIVE DEPOSITION METHOD

In the present research, to form niobium carbide coating on the surface of AISI L۲ steel Thermo-Reactive Deposition method (TRD) in a molten bath was used. Niobium carbide coating treatment was carried out at ۱۱۷۳ K, ۱۲۷۳ K, and ۱۳۷۳ K for ۲, ۴, and ۸ hours. The molten bath contained ۲۰wt.% borax (Na۲B۴O۷), ۵ wt.% boric acid (B۲O۳), and ۷۵ wt.% ferro-niobium. The presence and properties of the coated layer were studied by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) analysis. The thickness of coating ranged between ۶.۶ µm to ۳۳µm depending on treatment time, and temperature. The effects of treatment time and temperature on the coating thickness were studied. Kinetic study of the formation of NbC coating showed that growth of the coating is under the control of diffusion. The activation energy of the process was estimated to be ۱۲۲ kJ/mol. A practical formula to estimate the coating thickness was suggested.

کلیدواژه ها:

Surfaces ، Thermo-Reactive Deposition ، Carbide Coating