The influence of inclusions on the fatigue performance of a low pressure turbine blade steel

The 12% Cr steel FV566 is employed for low pressure turbine blade applications in UK based electrical generating plant. A comprehensive fatigue assessment on the alloy is reported to address the increasing use of such utilities under the low cycle fatigue conditions imposed by two shift operation. Fatigue experiments have been performed in atmospheric and vacuum environments at 20 °C and an elevated temperature typical of service. Data are included at various mean stress and frequency conditions. However, the greatest sensitivity in fatigue response was noted for specimens of different orientation with respect to the stock material. In particular, the dominating role played by oxide inclusions is highlighted. The implications for steam turbine applications are discussed.