B. S. Sidhu, GZS College of Engineering and Technology, Bathinda, India; H. S. Sidhu, Yadvindra college of Engineering, Bathinda, India; S. Prakash, Indian Institute of Technology, Roorkee, India, Roorkee, India
Cr2C3-NiCr, NiCr, WC-Co and Stellite-6 metallic coatings were sprayed on ASTM SA213-T11 steel by HVOF process. LPG was used as the fuel gas. The bared and HVOF sprayed specimens were exposed to molten salt at 9000C under cyclic conditions to evaluate hot corrosion behaviour. The thermo-gravimetric technique was used to establish kinetics of corrosion. The corrosion products were analysed by XRD, SEM/EDAX and EPMA techniques. The coatings showed better resistance to hot corrosion and NiCr Coating was found to be most protective followed by Cr2C3-NiCr coating. The formation of Cr2O3, NiO, NiCr2O4, and CoO phases may have contributed to the development of hot corrosion resistance in the coatings. The bared steel suffered corrosion in the form of intense spalling and peeling of the scale, which may be due to the formation of unprotective Fe2O3 oxide scale.
Summary: The manuscript deals with the evaluation of hot corrosion behaviour of HVOF sprayed boiler tube steel in molten salt environment. With the purpose of comparison the bare steel has also been tested in the given environment. The coatings were observed to provide the good protection to this boiler tube steel in the given environment i.e. Na2SO4-60%V2O5. The NiCr coating was found to be the most effective to increase the hot corrosion resistance of this boiler steel.
