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Reactions of calcium orthosilicate and barium zirconate with oxides and sulfates of various elements

Technical Report ·
OSTI ID:5795490
Calcium orthosilicate and barium zirconate were evaluated as the insulating layer of thermal barrier coatings for air-cooled gas turbine components. Surface temperatures of such coatings might reach 1300 to 1400/sup 0/C in hot spot locations. Thus chemical stability of these compounds was studied at 1100 and 1300/sup 0/C in the presence of some oxides and sulfates for times to 400 and 200 hours respectively. The oxides and sulfates studied represent some of the oxidation products of impurities found in the combustion air, or the fuels as well as the elements in the bond coat alloys. These compounds are listed below, according to their reactivity with calcium orthosilicate (actual composition was 1.78 CaO.SiO/sub 2/) and barium zirconate. When comparing these results with data available for reactions between similar compounds and ZrO/sub 2/-8w/oY/sub 2/O/sub 3/, it can be noted that all three materials reacted with SiO/sub 2/, P/sub 2/O/sub 5/, and V/sub 2/O/sub 5/. Also, zirconia was susceptible to attack by alkali and alkaline earth metal oxides. Calcium orthosilicate and barium zirconate were not susceptible to such attack but reacted readily with Al/sub 2/O/sub 3/ and Cr/sub 2/O/sub 3/, which did not react with ZrO/sub 2/-8w/oY/sub 2/O/sub 3/.
Research Organization:
National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
DOE Contract Number:
EF-77-A-01-2593
OSTI ID:
5795490
Report Number(s):
DOE/NASA/2593-79/9; NASA-TM-79272
Country of Publication:
United States
Language:
English