Development of a Novel, Impurity-Scavenging, Corrosion-Resistant Coating for Ni-Based Superalloy CMSX-4

Abstract

Sulfur, a common impurity arising from atmospheric and environmental contamination, is highly corrosive and detrimental to the lifespan of nickel superalloys in jet engines. However, sulfur-scavenging coatings have yet to be explored. Our study presents the successful development of a stable, uniform, impurity-scavenging Ni-Mn coating on Ni-based superalloy CMSX-4, through electroplating. The coating was characterised via combined scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. An optimal coating thickness of > 600 nm was deposited. The coated alloy was exposed to corrosive salt mixture 98% Na2SO4–2% NaCl at 550 °C for 100 h, mimicking engine exposure conditions, thereby proving that the coating successfully trapped sulfur and prevented its diffusion into an underlying alloy. This work presents a promising development for the prevention of sulfur-induced corrosion in industrial setting such as gas turbine engine, where the effects of sulfur diffusion into the bulk alloy could lead to premature failure. Graphical Abstract

A quantitative test method for the total corrosive or potentially corrosive sulfur in electrical insulating oil

“…Over the last decade there have been several failures of transformer and reactors reported from various countries [5][6][7][8][9] . Several analytical test techniques were used to investigate the reason for the failure and to understand the dynamics of the contamination.…”

Effect of NaCl and Na2SO4 on Low Temperature Corrosion of Vapour- and Pack-Aluminide Coated Single Crystal Turbine Blade Alloys CMSX-4 and RR3010

“…Nevertheless, coatings play an important role in the oxidation, and therefore the corrosion resistance, of their substrate. [ 14 , 15 ] Coatings can vary from low-cost diffusion-based processes, such as inward grown (pack)-aluminide coating, originally developed in the 1960 to 1970s, [ 12 ] from here onwards referred to as “pack aluminide”. Pack aluminide coatings rely on the nickel superalloy being heat treated to create inwards diffusion through the surface layer and therefore an “inward” growth of β -NiAl, capable of forming a stable, slow-growing, continuous Al 2 O 3 scale.…”