Air Oxidation and Hot Corrosion Behavior of Bare and CO₂ Laser-Welded Superalloy A-286 at 700 °C

Abstract

The present research work investigates the air oxidation and hot corrosion behavior of bare and CO₂ laser welded Fe-based superalloy A-286 in air and in simulated aero engine molten salt (Na₂SO₄–7.5%NaVO₃–5%NaCl) environment at 700 °C for 50 cycles. Spalling of oxide scales is observed in laser weldment in molten salt environment during hot corrosion study which is not observed in air-oxidized weldments at the end of 50 cycles. Corrosion kinetics of the weldments is obtained using the thermogravimetric technique. Scanning electron microscope/energy-dispersive spectroscopy and X-ray diffraction method are used to characterize the surface morphology and phase identification of the oxidized and hot-corroded weldments. Also, cross-sectional investigation is performed on the hot-corroded weldments to analyze the oxide scale thickness and distribution of alloying elements by optical/SEM microscopic and X-ray mapping analysis. The results show that higher corrosion rate is observed in the base metal compared to the weld zone and weldment. The grain refinement in the fusion zone facilitates the formation of Cr₂O₃ resulting in improved corrosion resistance in the fusion zone.