Cyclic Oxidation and Hot Corrosion Behaviour of Plasma Gun Sprayed Cermet Coatings on SS-304 Steel

Abstract

Power generation equipments, gas turbines and chemical plants face a serious problem of hot corrosion, due to which of the metallic components occurs. In the present study, S-304 boiler steel, that was being used in thermal power plant, has been investigated for its high temperature oxidation and hot corrosion behavior. Al₂O₃+13%TiO₂ , Al₂O₃+3%TiO₂ and Al₂O₃ powder was sprayed on the boiler steel using detonation gun thermal spraying process. The uncoated as well as coated S-304 samples were taken for being subjected to cyclic high temperature oxidation in air at 900°C and hot corrosion in molten salt environment of Na₂SO₄–60% V₂O₅, at 900°C, for 50 cycles. On performing high temperature oxidation study in air at 900°C, the maximum oxidation resistance was shown by Al₂O₃+13%TiO₂ with weight gain of 1.86% followed by Al₂O₃+3%TiO₂ with weight gain 2.36%. The weight gain for Al₂O₃ was 2.92%. The minimum resistance was shown by uncoated S-304 with weight gain of 3.91%.As a result of the study of hot corrosion in molten salt environment of Na₂SO4–60%V₂O₅ at 900°C, the weight gain percentages of Al₂O₃+13%TiO₂ coated, Al₂O₃+3%TiO₂ coated, Al₂O₃ coated and uncoated are 2.46%, 2.92%, 3.77% and 4.67% respectively. The protection obtained against hot corrosion followed the following sequence: Al₂O₃+13%TiO₂ coated > Al₂O₃+3%TiO₂ coated > Al₂O₃ coated > uncoated S-304 boiler steel.