Analysis of plasma gun sprayed coatings on SS-304 steel to evaluate cyclic oxidation and hot corrosion

Power plants, gas power turbines and chemical based plants face a very big issue of accelerated type of corrosion i.e hot corrosion, because of which the lifespan of metal decreased to large extent. In the present investigation, S-304 steel was taken which is commonly used in thermal power plants for inspection of accelerated corrosion i.e hot corrosion and high temp. oxidation behaviour. Alumina plus 13% titanium(Al2O3 + 13%TiO2), Alumina plus 3% titanium (Al2O3 + 3%TiO2) , Alumina(Al2O3)powder was applied on the boiler steel samples by using plasma spraying process. The uncoated and coated samples were exposed for 50 cycles to cyclic high temperature oxidation in air at 900 °C and hot corrosion in molten salt conditions of sodium sulphate and vanadium oxide (Na2SO4 – 60% V2O5) at 900 °C. In Oxidation study, with weight gain of 1.86% the upmost resistance against oxidation was exhibited by Alumina plus 13% titanium coated(Al2O3 + 13%TiO2) followed by Alumina plus 3% titanium coated (Al2O3 + 3%TiO2) with weight gain of 2.36% and by 2.92% by Alumina coated(Al2O3). The least resistance was shown by bare S-304 with weight gain of 3.91%.In investigation of hot corrosion, the weight gain percentages of Alumina plus 13% titanium coated(Al2O3 + 13%TiO2) is 2.46%, Alumina plus 3% titanium coated (Al2O3 + 3%TiO2) coated is 2.92%, Alumina coated(Al2O3) is 3.77% and for uncoated its 4.67%. The outcomes obtained for protection against oxidation and hot corrosion is: plus 13% titanium (Al2O3 + 13%TiO2) > Alumina plus 3% titanium (Al2O3 + 3%TiO2) coated > Alumina(Al2O3) > uncoated S-304 boiler steel.