Korean Journal of Materials Research (한국재료학회지)

Materials Research Society of Korea (한국재료학회)
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Grain Boundary Character Changes and IGA/PWSCC Behavior of Alloy 600 Material by Thermomechanical Treatment

가공열처리에 의한 Alloy 600 재료의 결정립계특성 변화와 입계부식 및 1차측 응력부식균열 거동

  • Kim, J. (Stem Generator Materials Projects, Korea Atomic Energy Research Institute) ;
  • Han, J.H. (Stem Generator Materials Projects, Korea Atomic Energy Research Institute) ;
  • Lee, D.H. (Stem Generator Materials Projects, Korea Atomic Energy Research Institute) ;
  • Kim, Y.S. (Dept. of Materials Engineering, Andong National University) ;
  • Roh, H.S. (Agency for Defense Development) ;
  • Kim, G.H. (Agency for Defense Development) ;
  • Kim, J.S. (Stem Generator Materials Projects, Korea Atomic Energy Research Institute)
  • 김진 (한국원자력연구소 증기발생기재료) ;
  • 한정호 (한국원자력연구소 증기발생기재료) ;
  • 이덕현 (한국원자력연구소 증기발생기재료) ;
  • 김영식 (안동대학교 재료공학과) ;
  • 노희숙 (국방과학연구소) ;
  • 김근홍 (국방과학연구소) ;
  • 김정수 (한국원자력연구소 증기발생기재료)
  • Published : 1999.09.01
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Abstract

Grain boundary characteristics and corrosion behavior of Alloy 600 material were investigated using the concept of grain boundary control by thermomechanical treatment(TMT). The grain boundary character distribution (GBCD) was analyzed by electron backscattered diffraction pattern. The effects of GBeD variation on intergranular at tack(JGA) and primary water stress corrosion cracking(PWSeC) were also evaluated. Changes in the fraction of coinci dence site lattice(CSL) boundaries in each cycle of TMT process were not distinguishable, but the total eSL boundary frequencies for TMT specimens increased about 10% compared with those of the commercial Alloy 600 material. It was found from IGA tests that the resistance to IGA was improved by TMT process. However, it was found from PWSCC test that repeating of TMT cycles resulted in the gradual decrease of the time to failure and the maximum load due to change in grain boundary characteristics, while the average crack propagation rate of primary crack increased mainly due to suppression of secondary crack propagation. It is considered that these corrosion characteristics in TMT specimens is attributed to 'fine tuning of grain boundary' mechanism.

가공열처리에 의한 결정립계조절 개념을 이용하여 Alloy 600 재료의 결정립계특성과 부식특성을 조사하였다. 가공열 처리에 따른 결정립계특성 변화를 EBSP로 분석하였으며, 결정립계특성 변화가 입계부식 및 응력부식균열 거동에 미치는 영향을 평가하였다. 가공열처리 반복에 따른 각 단계에서의 CSL 입계의 분율 변화가 두드러지지는 않았으나, 상용재료에 비하여 CSL 분율이 약 10% 이상 향상된 결과를 얻었다. 결정립계특성 변화에 따라 입계부식 저항성이 현저하게 증가하였으나, 1차측 응력부식균열 특성에 있어서는 가공열처리를 반복할수록 파단시간과 최대하중이 감소하고 평균 균열성장속도가 증가하였으며 2차 균열이 억제되는 결과를 얻었다. 결정립계의 \`fine tuning\` 기구가 이러한 부식거동변화에 작용한 것으로 해석할 수 있었다.

Keywords

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