Interactions Between Corrosion and Creep of Uncoated and Coated Superalloys in Sulfate Melts

摘要

Electrochemical corrosion measurements with Pt-containing (LDC-2) and Pt-free Al-diffusion coatings in the (Na, K)2 SO4 melt at 1173 K are summarized. The Pt-containing coating type exhibits a broader passive range than the Pt-free type. The Pt-free type corrodes significantly faster in the passive range than the Pt-containing type. The breakthrough potential for acidic fluxing is similar for both types. The Pt-containing type has a significantly higher resistance to basic fluxing. The breakthrough potential is 300 mV more negative than that of the Pt-free type. Creep tests with IN 939 in the (Na2, Mg, Ca) SO4 melt under potentiostatic control at 1073 K show that potential affects creep behavior, due to a reduction of the load bearing cross section due to corrosion.