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Study for Fracture in the Last Stage Blade of a Low Pressure Turbine
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 Title & Authors
Study for Fracture in the Last Stage Blade of a Low Pressure Turbine
Lee, Gil Jae; Kim, Jae Hoon;
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 Abstract
The last stage blades of a low pressure (LP) turbine get frequently fractured because of stress corrosion cracking. This is because they operate in a severe corrosive environment that is caused by the impurities dissolved in condensed steam and high stress due to high speed rotation. To improve the reliability of the blades under severe conditions, 12% Cr martensitic stainless steel, having excellent corrosion resistance and higher strength, is widely used as the blade material. This paper shows the result of root cause analysis on a blade which got fractured suddenly during normal operation. Testing of mechanical properties and microstructure examination were performed on the fractured blade and on a blade in sound condition. The results of testing of mechanical properties of the fractured blade showed that the hardness were higher but impact energy were lower, and were not meeting the criteria as per the material certificate specification. This result showed that the fractured blade became embrittled. The branch-type crack was found to have propagated through the grain boundary and components of chloride and sulfur were detected on the fractured surface. Based on these results, the root cause of fracture was confirmed to be stress corrosion cracking.
 Keywords
Thermal Power Plant;Low Pressure Turbine;Stress Corrosion Cracking;Intergranular Crack;
 Language
Korean
 Cited by
 References
1.
Song, G. W., Choi, W. S., Kim, W. J. and Jung., N. G., 2013, "Damage Analysis for Last-Stage Blade of Low-Pressure Turbine," Trans. Korean Soc. Mech. Eng., Vol. 37, No. 12, pp. 1153-1157. crossref(new window)

2.
Timo, D. P. and Sarney, G. W., 1967, "The Operation of Large Steam Turbine to Limit Cyclic Thermal Cracking," ASME 67-WA/PWR-4, pp. 3-15.

3.
Zdzislaw Mazur, Rafael Garcia-Illescas, Jorge Aguirre-Romano, Norberto Perez-Rodriguez., 2008, "Steam Turbine Blade Failure Analysis," Engineering Failure Analysis, Vol. 15, No. 1-2, pp. 129-141. crossref(new window)

4.
Irvine, Crowe, Pickering, 1971, "The Making, Shaping, and Treating of Steel," 9th ed., pp. 1178.

5.
Gopa Chakraborty, CR. Das, S. K. Albert, A. K. Bhaduri, V. Thomas Paul, G.Panneerselvam, Arup Dasgupta., 2015, "Study on Tempering Behaviour of AISI 410 Stainless Steel," Materials Characterization, Vol. 100, pp. 81-87. crossref(new window)

6.
ASM Metals Handbook, 9th ed., 1981, "Heat Treating of Stainless Stees," Vol. 4, p. 635

7.
Pawlowski, B., Mazur, A. and Gorczyca, S., 1991, "The Effect of the Tempering Processes on the Susceptibility to Stress Corrosion Cracking of High Strength Steel," Corrosion Science, Vol. 32, pp. 685-691. crossref(new window)