Breakaway oxidation of a low-Al content nanocrystalline coating at 1000 °C

Steam oxidation of scratched β‐FeAl coatings on P92 steel

“…However, the low aluminum content resulted in the formation of particulate Al 2 O 3 along the outermost Fe oxide layer and doped in the iron oxide (Fe 2 O 3 + Fe 3 O 4 ) at the scale/scratch interface with the growth of the bi‐layer oxide scale. [ 36 ] The bi‐layer Fe‐rich oxide film on the scratched track grew radially, which is similar to the oxide scale formed on the bare P92 steel. The thermal expansion coefficients of the bi‐layer Fe‐rich oxide film and the substrate were quite different, so the oxide scale was undergoing severe thermal stress and growth stress.…”

Effect of γ′ Phase Elements on Oxidation Behavior of Nanocrystalline Coatings at 1050 °C

“…Nanocrystalline coating has attracted much attention for its excellent high-temperature oxidation resistance [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Since Lou invented nanocrystalline coating in 1992, the research of nanocrystalline coating has been developed for nearly 30 years, and more than 30 kinds of alloys have been well-studied [ 28 ].…”

“…The coating is made up of a columnar crystal at nano size, which promotes the rapid diffusion of Al in the coating and the fast formation of the Al 2 O 3 scale. At the same time, the chemical compositions of the coating are the same with the superalloy, which can avoid a series of problems caused by diffusion [ 24 , 28 , 29 , 30 ]. Then, the service life of the coating can be prolonged.…”

“…Then, the service life of the coating can be prolonged. The deposited nanocrystalline coating consists only of supersaturated γ phase, in which all elements, including the γ′ phase elements, are dissolved and very unstable [ 21 , 22 , 23 , 24 , 25 , 26 ]. During service, the γ′ phase elements will be separated from the supersaturated γ phase, and the γ′ phase can be formed.…”