Solid/Molten Na₂SO₄-Induced Hot Corrosion Behaviors of Mar-M247 Alloy with CVD Aluminide Coatings

Aluminide coatings were prepared by chemical vapor deposition (CVD) method on Ni-based superalloy Mar-M247 to improve the corrosion resistance. The Na₂SO₄-induced hot corrosion behavior of Mar-M247 with and without aluminide coating was investigated at varying temperatures. The results revealed that the substrate underwent relatively mild corrosion attack at temperatures below the Na₂SO₄ melting point, but extremely severe corrosion attack above it. The aluminide coating significantly improved the corrosion resistance of the substrate, with the formation of Al₂O₃ scale during corrosion. The effects of both solid and molten Na₂SO₄ on hot corrosion resistance of Mar-M247 alloy and its aluminide coating was discussed, as well as the detrimental effect of tungsten on the substrate in ‘type I’ hot corrosion.