J. Kimmel et al. Journal of the European Ceramic Society 22(2002)2769-2775 2775 3. Concluding remarks Acknowledgements The CfCc inner and outer liners used in the fifth This work was performed under DOE Contracts DE CSGT field test(13, 937 h) were destructively and non- ACo2-92CE40960 and DE-FC02-00CH11049. We are destructively evaluated. The EBCs spalled off at the aft- grateful to Stephen Waslo and Jill Jonkouski of the DOe end edges of both liners. The combustor design was Chicago Operations Office, and Patricia Hofman and modified to minimize/eliminate the spallation in the Debbie Haught of the DOE Office of Power Technologies sixth field test at Texaco. Several pinholes were for their technical and programmatic support. We observed on the outer liner, many of which correlated appreciate the contributions and guidance of Jerry Woods, with a repeatable pattern of surface asperities in the as- Don Leroux, Anthony Fahme, Zaher Mutasim, and Mark protected the liners effectively in the berities. The EBC HACL, Bill Ellingson, J.G. Sun and Chris Deemer ofA fabricated liner. The CFCC liner fabrication process is van Roode of Solar, Dennis Landini and Ali Fareed being modified to reduce surface a herethere was no spallation or localized oxidation. The (u ended) thick SiC seal coat layer was partly responsible References for the inner liner surviving almost 14,000 h despite a 1. Miriyala, N. Fahme, A and van Roode, M, Ceramic stationary major EBC spall in the earlier part(900 h) of the test as turbine program--combustor liner development summary The nDe techniques could detect flaws in the EBC ASME Paper 2001-GT-512, presented at the International Gas inner liner. the location of which correlated with the Turbine and Aeroengine Congress and Exposition, New Orleans major spall observed during the field test. Recession of LA. USA. June 2001 the Bsas top layer was observed, but even after partial 2. Eaton, H.E. et al. EBC protection of SiC/SiC composites in the as turbine combustion environment. ASME Paper 2000-GT BSAS recession the EBC was still protective. In order to 231, presented at the International Gas Turbine and Aeroengine reduce BSAS recession in future engine tests, either its Congress and Exposition, Munich, Germany, May 2000. ckness can be increased or the composition modified 3. Opila, E J and Hann, R. E, Paralinear oxidation of CVD SiC in to achieve a more resistant top layer. The three-layer 4. Pila. E.et al. sic recession due to s EBC system used on the outer liner was better than that combustion conditions. Part Il: thermodynamics and gaseous used on the inner liner. The addition of bsas to mullite diffusion model. J. Am. Ceram Soc. 1999, 827. 1826-1834 in the intermediate layer minimized /reduced cracks in 5. Jacobson. N. S. Corrosion of silicon-based ceramics in combus- that layer, resulting in better protection of the liner tion environments. J. Am. Ceram. Soc., 1993, 761. 3-28 However, the stability of mullite in the combustion of ceramics and ceramic matrix ites in simulated and actua tor environments environment appears to be an issue. The use of EBC ASME Paper 1999-GT-292, presented International gas coating increased the life of CFCC liners from approxi- Turbine and Aeroengine Congress and on, Indianapolis, mately 5000 to 14,000 h, roughly a 3-fold increase. It IN. USA. June 1999 appears that by avoiding/minimizing surface asperities 7. Elingson, WA. Sun, J.G. More, KL and Hines, R- Non- during the manufacture of the liners and making a few EBC compositional and processing changes, the desired bustor liners in advanced gas turbines. ASME Paper 2000-GT-68 presented at the International Gas Turbine and Aeroengine liner life of 30,000 h could potentially be achieved ongress and Exposition, Munich, Germany, May 20003. Concluding remarks The CFCC inner and outer liners used in the fifth CSGT field test (13,937 h) were destructively and non￾destructively evaluated. The EBCs spalled off at the aft￾end edges of both liners. The combustor design was modified to minimize/eliminate the spallation in the sixth field test at Texaco. Several pinholes were observed on the outer liner, many of which correlated with a repeatable pattern of surface asperities in the as￾fabricated liner. The CFCC liner fabrication process is being modified to reduce surface asperities. The EBC protected the liners effectively in the areas where there was no spallation or localized oxidation. The (unin￾tended) thick SiC seal coat layer was partly responsible for the inner liner surviving almost 14,000 h despite a major EBC spall in the earlier part (900 h) of the test. The NDE techniques could detect flaws in the EBC inner liner, the location of which correlated with the major spall observed during the field test. Recession of the BSAS top layer was observed, but even after partial BSAS recession the EBC was still protective. In order to reduce BSAS recession in future engine tests, either its thickness can be increased or the composition modified to achieve a more resistant top layer. The three-layer EBC system used on the outer liner was better than that used on the inner liner. The addition of BSAS to mullite in the intermediate layer minimized/reduced cracks in that layer, resulting in better protection of the liner. However, the stability of mullite in the combustion environment appears to be an issue. The use of EBC coating increased the life of CFCC liners from approxi￾mately 5000 to 14,000 h, roughly a 3-fold increase. It appears that by avoiding/minimizing surface asperities during the manufacture of the liners and making a few EBC compositional and processing changes, the desired liner life of 30,000 h could potentially be achieved. Acknowledgements This work was performed under DOE Contracts DE￾AC02-92CE40960 and DE-FC02-00CH11049. We are grateful to Stephen Waslo and Jill Jonkouski of the DOE Chicago Operations Office, and Patricia Hoffman and Debbie Haught of the DOE Office of Power Technologies for their technical and programmatic support. We appreciate the contributions and guidance of Jerry Woods, Don Leroux, Anthony Fahme, Zaher Mutasim, and Mark van Roode of Solar, Dennis Landini and Ali Fareed of HACI, Bill Ellingson, J.G. Sun and Chris Deemer of ANL. References 1. Miriyala, N., Fahme, A. and van Roode, M., Ceramic stationary gas turbine program—combustor liner development summary. ASME Paper 2001-GT-512, presented at the International Gas Turbine and Aeroengine Congress and Exposition, New Orleans, LA, USA, June 2001. 2. Eaton, H.E. et al., EBC protection of SiC/SiC composites in the gas turbine combustion environment. ASME Paper 2000-GT- 231, presented at the International Gas Turbine and Aeroengine Congress and Exposition, Munich, Germany, May 2000. 3. Opila, E. J. and Hann, R. E., Paralinear oxidation of CVD SiC in water vapor. J. Am. Ceram. Soc., 1997, 80[1], 197–205. 4. Opila, E. J. et al., SiC recession due to SiO2 scale volatility under combustion conditions. Part II: thermodynamics and gaseous diffusion model. J. Am. Ceram. Soc., 1999, 82[7], 1826–1834. 5. Jacobson, N. S., Corrosion of silicon-based ceramics in combus￾tion environments. J. Am. Ceram. Soc., 1993, 76[1], 3–28. 6. More, K.L. et al., Exposure of ceramics and ceramic matrix composites in simulated and actual combustor environments. ASME Paper 1999-GT-292, presented at the International Gas Turbine and Aeroengine Congress and Exposition, Indianapolis, IN, USA, June 1999. 7. Ellingson, W.A., Sun, J.G., More, K.L., and Hines, R., Non￾destructive characterization of ceramic composites used as com￾bustor liners in advanced gas turbines. ASME Paper 2000-GT-68, presented at the International Gas Turbine and Aeroengine Congress and Exposition, Munich, Germany, May 2000. J. Kimmel et al. / Journal of the European Ceramic Society 22 (2002) 2769–2775 2775