STUDY ON VANADIUM CARBIDE COATING FORMATION ON AISI L۲ STEEL BY THERMO-REACTIVE DEPOSITION TECHNIQUE

Abstract: The possibility of vanadium carbide coating formation on AISI L۲ steel was studied in molten salt bath containing ۳۳ wt% NaCl- ۶۷ wt% CaCl۲. In this research, the effects of time, temperature and bath composition on growing layer thickness were studied. The vanadium carbide coating treatment was performed in the NaCl-CaCl۲ bath at ۱۱۷۳, ۱۲۷۳ and ۱۳۷۳ K temperatures for ۳, ۶, ۹ hours and in bath containing ۵, ۱۰, ۱۵, ۲۵ wt% ferrovanadium. The presence of VC formed on the surface of the steel substrate was confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis. The layer thickness of vanadium carbide and surface hardness ranged between ۴.۸ to ۲۵.۷ µm and ۲۶۴۵ to ۳۶۰۰ HV, respectively. The kinetics of layer growth was analyzed by measuring the depth of vanadium carbide layer as a function of time and temperature. The mean activation energy for the process is estimated to be ۱۳۳ kJ/ mol.