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The nitrogen‐supersaturated phase produced by low‐temperature plasma‐assisted nitriding of austenitic stainless steel usually contains a high density of stacking faults. However, the stacking fault density observed in previous studies was considerably lower than that determined by fitting the X‐ray diffraction pattern. In this work, it has been confirmed by high‐resolution transmission electron microscopy that the strip‐shaped regions of about 3–25 nm in width observed at relatively low magnification essentially consist of a series of stacking faults on every second {111} atomic plane. A microstructure model of the clustered stacking faults embedded in a face‐centred cubic structure was built for these regions. The simulated X‐ray diffraction and transmission electron microscopy results based on this model are consistent with the observations.

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In order to protect carbon/carbon (C/C) composites against oxidation, a Si–Mo–W coating was prepared on the surface of SiC‐coated C/C composites by a simple reaction method. The microstructures of the as‐received coating were characterized by scanning electron microscopy, X‐ray diffraction, and energy dispersive spectroscopy analyses. The results show that the SiC/Si–Mo–W coating can protect C/C composites from oxidation in air at 1673 K for 220 h with a mass loss of 0.003%, and at 1773 K for 252 h with a mass gain of 1.56%. The excellent oxidation‐resistant property of the SiC/Si–Mo–W coating at 1673–1773 K is attributed to the formation of SiO2 film on the coating surface. The mass loss of the coated C/C composites during the oxidation test at 1873 K in air primarily resulted from the reaction of C/C substrate and oxygen diffusing through the penetration cracks in the coating.

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