As steam power plants continue to move towards higher operating temperatures in order to improve efficiency, materials exposed to the working fluid are subjected to premature failures. In this study, the performance of a CoCrMoSi (T14) and CoCrNiMoSi (T19) was evaluated in superheated steam (SHS, 0.1MPa) at 800minor-fareast;mso-ansi-language:EN-CA;mso-fareast-language:ZH-CN;mso-bidi-language:
AR-SA">ºC. After exposure, both T14 and T19 experienced weight gain caused by oxidation. Visual observation and SEM surface analysis revealed that T19 had greater surface oxide spallation than T14. From the cross sectional evaluation, however, a thin, adherent oxide layer was found to have formed on T19. T14 had suffered from excessive internal oxidation (up to a depth of 30 µm) and the surface oxide was uneven and had signs of cracking. Based on the results obtained, it seems that the finer Laves phase (due to Ni addition) combined with greater Cr content in the T19 has led to the formation of seemingly protective oxide layer. Due to the extensive internal oxidation, T14 is not suitable for applications in SHS at 800minor-fareast;mso-ansi-language:EN-CA;mso-fareast-language:ZH-CN;mso-bidi-language:
AR-SA">ºC.