CHARACTERSATION & HOT CORROSION STUDIES ON PLASMA SPRAYED (WC-CO) / (CR3C2-NICR) COATING ON TITANIUM & SPECIAL STEEL ALLOYS

A present study is an attempt to evaluate the hot corrosion resistance of plasma sprayed 35%(WC-Co)+65 %(Cr3C2-NiCr) coatings on Titanium-15 & MDN 420 alloys in molten salt environment of Na2SO4+60 %V2O5 salt mixture at 700oC under cyclic conditions. The hot corrosion tests are carried out for 50 cycles, for 1 hour each cycle of heating followed by 20 minutes of cooling in open air environment. The tests are conducted in silicon carbide tubular furnace. Thermogravimetric studies are made to establish the kinetics of corrosion for the uncoated and coated samples. The SEM/EDS, XRD & X-ray elemental mapping techniques are made to analyze the parameters like element concentration, morphology, & phase composition & of the hot corrosion products. The parabolic rate constants are evaluated for understanding the corrosion behavior of coatings. It is observed that (WC-Co) + (Cr3C2-NiCr) coated MDN-420 is more resistant than coated (WC-Co) + (Cr3C2-NiCr) coated titanium-15. From the present study it is concluded that the hot corrosion resistance of both the coatings has been attributed to the formation of Ni3V208, NiCr2O4, NiWO4, and COCr2O4 & Cr3C2.