Low cycle fatigue behavior of 12Cr tempered martensitic steel as the candidate bucket material for USC power plant

The objective of this study is to investigate the characteristics of low cycle fatigue for the candidate bucket material (DS2B2) developed by Doosan. Turbine bucket is subjected to the repeated thermal stress during shutdown and heat-up. Therefore, LCF characteristics is of much concern in order to meet the fatigue life requirement. At room and service temperature of 593 .deg. C, LCF test were carried out for DS2B2 and commercial materials COST B2. Both DS2B2 and COST B2 materials were refined by VIM and ESR process. DS2B2 material was more superior to COST B2 for LCF life. The LCF characteristics of DS2B2 materials manufactured by VIM and ESR processes was improved as compared with that by VIM process. It can be seen that the harmful element S and non-metallic inclusions were reduced and the grain size was finer through the ESR refining process