화학공학소재연구정보센터
Materials Science Forum, Vol.461-464, 907-915, 2004
Development of a new test method of high temperature corrosion in gas turbines based on thermodynamic modelling
The hot corrosion risk in stationary gas turbines is re-evaluated for the new material combinations and the changed fuel quality. Hot corrosion can only be induced, if the condensation of corrosive species, e.g. sulphates, is possible. The risk of sulphate-induced hot corrosion is directly dependent on the total amount of impurities in the hot gas and the pressure. The evaluation of the risk is done based on thermodynamic modelling of the dew point of the corrosive salts. Based on the theoretical approach a laboratory corrosion test was designed. The test method is based on a salt-spraying test. The exposure is performed in dry air with 300vppm SO2 and 10vol% H2O, with the main test temperatures 700degreesC and 850degreesC. The hot corrosion behaviour of three base materials, IN738, CM247 and CMSX-4, and the NiCrAlY-coating SV20 were investigated with the new test method. IN738 exhibited the best corrosion resistance of the base materials, but was also attacked after 500h. The base materials, especially CM247 and CMSX-4, have to be protected by an oxidation- and corrosion-resistant overlay coating in a corrosive environment. They can only be used without a protective coating, when a clean environment can be guaranteed. SV20 has exhibited an excellent corrosion resistance with negligible degradation after 1000h at 700 and 850degreesC.