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An aluminide(AlFe and α-(FeAl)) surface layer containing lower-Al was formed on ferritic-martensitic steel P92 by means of surface mechanical attrition treatment(SMAT) combined with a duplex aluminization process at lower temperatures,i.e.a packed aluminization followed by a diffusion annealing treatment below its tempering temperature.Indentation tests indicated that the lower-Al surface layer formed on the SMAT sample is more resistant to cracking and has better adhesion to the substrate in comparison with the Al_5Fe_2 layer formed on the as-received sample after the duplex aluminization process.Isothermal steam oxidation measurements showed that the oxidation resistance is increased significantly by the lower-Al surface layer due to the formation of a protective(Fe,Cr)Al_2O_4 layer.The rate constant of oxidation was estimated to decrease from-0.849 mg~2 cm~(-4)h~(-1) of the as-received material to~0.011 mg~2 cm~(-4) h~(-1) of the AlFe layer at 700 ℃.
An aluminide (AlFe and α- (FeAl)) surface layer containing lower-Al was formed on ferritic-martensitic steel P92 by means of surface mechanical attrition treatment (SMAT) combined with a duplex aluminization process at lower temperatures, iea packed aluminization followed by a diffusion annealing treatment below its tempering temperature. Indentation tests indicated that the lower-Al surface layer formed on the SMAT sample is more resistant to cracking and has better adhesion to the substrate in comparison with the Al_5Fe_2 layer formed on the as-received sample after the duplex aluminization process. Isothermal steam oxidation measurements showed that the oxidation resistance is greatly increased by the lower-Al surface layer due to the formation of a protective (Fe, Cr) Al_2O_4 layer. The rate constant of oxidation was estimated to decrease from- 0.849 mg ~ 2 cm ~ (-4) h ~ (-1) of the as-received material to ~ 0.011 mg ~ 2 cm ~ (-4) h ~ (-1) of the AlFe layer at 700 ℃.