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Evaluation of High Temperature Material Degradation for 12Cr Steel by Electrochemical Polarization Method

전기화학적 분극법을 이용한 12Cr강의 고온 재질열화도 평가

  • 서현욱 (중앙대학교 대학원 기계공학부) ;
  • 박기성 (한양대학교 대학원) ;
  • 윤기봉 (중앙대학교 기계공학부)
  • Published : 2006.08.01

Abstract

High pressure turbine blades are one of the key components in fossil power plants operated at high temperature. The blade is usually made of 12Cr steel and its operating temperature is above $500^{\circ}C$. Long term service at this temperature causes material degradation accompanied by changes in microstructures and mechanical properties such as strength and toughness. Quantitative assessment of reduction of strength and toughness due to high temperature material degradation is required for residual life assessment of the blade components. Nondestructive technique is preferred. So far most of the research of this kind was conducted with low alloy steels such as carbon steel, 1.25Cr0.5Mo steel or 2.25Cr1Mo steel. High alloy steel was not investigated. In this study one of the high Cr steel, 12Cr steel, was selected for high temperature material degradation. Electrochemical polarization method was employed to measure degradation. Strength reduction of the 12Cr steel was represented by hardness and toughness reduction was represented by change of transition temperature, FATT. Empirical relationships between the electrochemical polarization parameter and significance of material degradation were established. These relationship can be used for assessing the strength and toughness on the aged high pressure blade components indirectly by using the electrochemical method.

Keywords

12Cr Steel;Electrochemical Polarization Method;Material Degradation;Turbine Blade;Life Assessment;FATT;Ageing

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