The Control of Sulfur Content in Nickel-Base, Single Crystal Superalloys and Its Effects on Cyclic Oxidation Resistance
| Autor: | I. R. Blachere, C. Stinner, James L. Smialek, N. Birks, Gerald H. Meier, Frederick S. Pettit, Cevat Sarioglu |
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| Rok vydání: | 1996 |
| Předmět: |
Nial
Materials science Alloy Metallurgy technology industry and agriculture Oxide chemistry.chemical_element Temperature cycling engineering.material equipment and supplies Sulfur Flue-gas desulfurization Superalloy chemistry.chemical_compound Cerium chemistry engineering computer computer.programming_language |
| Zdroj: | Superalloys 1996 (Eighth International Symposium). |
| DOI: | 10.7449/1996/superalloys_1996_71_80 |
| Popis: | State-of-the-art superalloys are useful for high temperature applications, in large part, because they form protective alumina surface films by the selective oxidation of aluminum from the alloy. The adherence of the alumina to the alloy is crucial to maintaining oxidation resistance, particularly under thermal cycling conditions. It is now well established that small additions of reactive elements, such as yttrium hafnium, and cerium substantially improve the adherence of alumina films to alloy substrates. While the effects produced by the reactive elements are widely known the mechanisms whereby they improve adherence are not completely understood. Over the last fifty years a number of mechanisms have been proposed. However, it has recently become clear that a major effect of the reactive elements is to tie up sulfur in the alloy and prevent it from segregating to the alloy/oxide interface and weakening an otherwise strong bond. This paper describes the results of a study of the control of sulfur content in alumina-forming nickel-base superalloys and NiAl by three methods: 1. Addition of Reactive Elements (Y and Hf). 2. Desulfurization in the solid state. 3. Desulfurization in the liquid state. Additionally, calculations have been performed to determine how much sulfur is available to segregate to the scale/alloy interface and how this quantity is influenced by the type and amount of reactive element in the alloy and the level to which the alloy is desulfurized. Finally, the results from experiments to desulfurize the alloys are described and cyclic oxidation measurements are used to evaluate the calculations. |
| Databáze: | OpenAIRE |
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