Thermo-reactive deposition processed vanadium carbide coating: growth kinetics model and diffusion mechanism

A mathematical model on the growth kinetics of vanadium carbide coatings on steels by thermo-reactive deposition/diffusion (TRD) process was constructed. It takes into account the influence of substrate compositions on the growth rates of the carbide coatings. The model takes the carbon activity in the substrate to characterize the influence of carbon and alloy elements in substrate on the coating thickness. The relationship of coating thickness and the carbon activity follows a parabolic law. The proposed growth kinetics model shows relatively in good agreement with experimental data. The diffusivity of carbon in the vanadium carbide coating is calculated to be about four orders of magnitude higher than that in the vanadium carbide lattice, thus carbon diffusion along grain boundaries of vanadium carbides dominates the growth of the coatings formed in the TRD process.