Comparative Isothermal Oxidation Resistance of Selected Single-Crystal Ni-Based Superalloys With and Without Pt-Modified Surface Layers

摘要

Isothermal oxidation tests at 1150 degrees C show that the commercial grade of the single-crystal Ni-based superalloy CMSX-4 is superior to that of the CMSX-10 version. Superalloy CMSX-4 is observed to undergo a shorter stage of transient oxidation and to be able to form more protective oxides during the earlier stages of the reaction as compared to superalloy CMSX-10. This behavior is correlated with the difference in chemical composition between the two superalloys. A significant improvement in oxidation resistance of both superalloys is realized after diffusing a 10 mu m thick layer of Pt into their surfaces to produce a Pt-rich surface layer of gamma '-phase. However, the oxidation resistance of the composite Pt/CMSX-10 system becomes superior to that of the Pt/CMSX-4 system. Most evidence indicates that this is a reflection of the higher microstructural stability of the gamma '-phase in superalloy CMSX-10 and the added beneficial effect provided by Pt.