Evaluation and Performance of TD Cobalt Alloys as Guide Vanes in Gas Turbine Engines.
Final rept. 1 Jun 69-15 Oct 70,
PRATT AND WHITNEY AIRCRAFT WEST PALM BEACH FL FLORIDA RESEARCH AND DEVELOPMEN T CENTER
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Laboratory and engine testing of two experimental thoria-cobalt compositions Co-20Ni-18Cr-2ThO2 and Co-20Ni-3oCr-2ThO2 were conducted to define alloy applicability to turbine vane airfoils in advanced turbomachinery. Extrusion studies were conducted initially to define acceptable forming parameters for airfoil fabrication from a powder compact. Results showed that those conditions imposing the most severe deformation enabled recrystallization to a product that had high tensile and creep-rupture strength. Without complete recrystallization or with recrystallization causing a duplexed fine-coarse grain structure, the alloys did not exhibit maximum strength. Concurrent studies of corrosion resistance and protective coating application showed that the higher chromium alloy could withstand an oxidizing environment to approximately 2200F without serious degradation although, where salt-sulfur reaction products contributed to metal attack, a protective coating was found necessary. The lower chromium alloy had lower resistance, as expected, and protective coating was considered necessary for all operations involving sustained exposures at high temperatures. A vapor deposited CoCrA1Y composition proved to be a satisfactory coating for both alloys. First stage turbine vane assemblies for the TF30 engine were fabricated from each alloy and engine tested for 150 hr under qualification test endurance conditions. The experimental compositions were used as airfoils to the assemblies and were brazed to Mar-M 302 platforms. Coated and uncoated vanes were run. Author
- Metallurgy and Metallography
- Jet and Gas Turbine Engines