| Autor: |
Molodtsov, Artjom, Dedov, Andrei, Klevtsov, Ivan, Kommel, Lembit, Lausmaa, Toomas, Mikli, Valdek |
| Zdroj: |
Key Engineering Materials; April 2019, Vol. 799 Issue: 1 p89-94, 6p |
| Abstrakt: |
This work presents an experimental case study of 200 MW low-pressure steam turbine rotor blades damage after 310 thousand hours of operation and 404 start-ups on the power plant. Damaged blade material was analysed by experimental testing of mechanical properties as well as crack initiation and microstructure in the damaged area by using optical and scanning electron microscopes, and investigation of chemical composition by the SEM-EDS method. Results of the investigation show that the material was die forged martensitic steel 20Cr13. The mechanical properties of the blade steel were in accordance with standard technical requirements for new material. The cross-sections of damaged and undamaged blades were investigated and compared. It was found that thickness of damaged blades was significantly less than undamaged ones. SEM-EDS analysis has shown the presence of brass fragment on the surface of one damaged blade. The microstructural analysis has shown that one of the cracks was initiated due to impact of brass fragment. Based on the given case study results it is concluded that the reason of the blade damage was a combination of at least two factors: accelerated high cycle fatigue due to increased stresses caused by excessive vibration of damaged blades with lower thickness and impact of brass fragment against blades. |
| Databáze: |
Supplemental Index |
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