Fig. 1 Surface views of a Al2O3-, b Fe2O3-coated Ni-10Cr alloy samples

Fig. 2 Dependence of a weight gain, b weight gain square on time for the bare, Al2O3- and Fe2O3-coated Ni-10Cr alloy

Fig. 3 XRD patterns of bare, Al2O3- and Fe2O3-coated Ni-10Cr alloy after oxidation for 20 h at 800 °C

Fig. 4 a BSE-SEM cross-section, b corresponding EDS mappings of bare Ni-10Cr alloy after oxidation for 20 h at 800 °C

Fig. 5 a BSE-SEM cross-section, b corresponding EDS mappings of Fe2O3-coated Ni-10Cr alloy after oxidation for 20 h at 800 °C

Fig. 6 a BSE-SEM cross-section of Al2O3-coated Ni-10Cr alloy after oxidation for 20 h at 800 °C, b the enlarged view of the framed region in a

Fig. 7 TEM characterizations of the scale developed by the Fe2O3-coated Ni-10Cr alloy: a bright field image of the scale, a’ HADDF-STEM image of the yellow framed area in a, b corresponding EDS mappings of a, c and d SAED patterns for Points 3 and 4, respectively, e and f HRTEM and corresponding FFT images of the Cr2O3 phase in the scale, g HRTEM image of the red framed region in a’

Fig. 8 TEM characterizations of the scale developed by the Al2O3-coated Ni-10Cr alloy: a bright field image of the scale, a’ HADDF-STEM image of the yellow framed area in a, b corresponding EDS mappings of a, c and d SAED patterns for Points 5 and 6, respectively, e HRTEM image of the red framed region in a’ and corresponding FFT patterns of the α-Al2O3 and Cr2O3 phases

Fig. 9 Schematic diagram of the oxidation mechanism of Ni-10Cr alloy with surface spraying hcp-structured oxide nanoparticles at 800 °C in air