The performance of metallic honeycomb sections has been studied under thermal cycling conditions involving their exposure to a simulated natural gas combustion environment for total exposure times of up to 2,520 hours. Samples manufactured from PM2000 and Haynes 214 were tested at temperatures of 950, 1050, 1100 and 1150degreesC and cycled on a weekly basis with 15 thermal cycles between room temperature and the test temperature. Samples of Nimonic 86 were included in the test at 950degreesC for comparison. The performance of the materials during the tests was monitored using weight change data. More useful dimensional metrology data were derived from surface and cross-sectional oxide thickness and metal-loss measurements on specimens examined after 15 thermal cycles (and after fewer cycles at higher temperatures - if significantly enhanced oxidation attack had been experienced by the alloys). After 2,520 hours at 1100 and 1150degreesC, both PM2000 and Haynes 214 were either totally oxidised or showed very significant damage. At 1050degreesC, however, the materials performed much better, with little to distinguish them, except Haynes 214 had more internal corrosion damage in places. Damage levels were lower still at 950degreesC, with Nimonic 86 having higher weight gains and thicker surface oxides than the other two materials. Overall, this study has shown that there is still a lot of development work required in order to move to higher temperature sealing systems utilizing honeycomb structures in gas turbine applications.
