PWR 1차측 환경에서 Alloy 600 응력부식균열 선단 부근에서의 산화 거동

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임연수;김홍표;황성식
Lim, Yun Soo;Kim, Hong Pyo;Hwang, Seong Sik

  • 투고 : 2012.07.03
  • 심사 : 2012.08.13
  • 발행 : 2012.08.31

초록

Stress corrosion cracks in Alloy 600 compact tension specimens tested at $325^{\circ}C$ in a simulated primary water environment of pressurized water reactor were analyzed by analytical transmission electron microscopy and secondary ion mass spectroscopy (SIMS). From a fine-probe chemical analysis, oxygen was found on the grain boundary just ahead of the crack tip, and chromium oxides were precipitated on the crack tip and the grain boundary attacked by the oxygen diffusion, leaving a Cr/Fe depletion (or Ni enrichment) zone. The oxide layer inside the crack was revealed to consist of a double (inner and outer) layer. Chromium oxides existed in the inner layer, with NiO and (Ni,Cr) spinels in the outer layer. From the nano-SIMS analysis, oxygen was detected at the locations of intergranular chromium carbides ahead of the crack tip, which means that oxygen diffused into the grain boundary and oxidized the surfaces of the chromium carbides. The intergranular chromium carbide blunted the crack tip, thereby suppressing the crack propagation.

키워드

Alloy 600;PWSCC;TEM;SIMS;grain boundary;oxygen diffusion

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과제정보

연구 과제 주관 기관 : 과학기술부