A study on the stress dependence of diffusion coefficient at the elevated tenperature and the structural characterictics of 12% Cr rotor steel.

J. Ocean Eng. Technol. 1997;11(2):39-47.

12% Cr강의 고온 확산계수의 응력의존성과 조직의 특성에 관한 연구

장윤석,김태형

정회원 경남전문대 기계설계과,동아대학교 생산기술 연구소

Keywords: Bulk self diffussion coefficient, Equivalent self diffussion coefficient, Effective self diffussion coefficient

핵심용어: 체적자기확산계수, 상당자기확산계수, 유효확산계수

Abstract

Creep rate the elevated temperature is known to be controller by the softening process of microstructure especially in the solid solution alloys such as 125 Cr rotor steel. The change of structure is a decreasing process of the free energy of the state including stress, diffusivity of the material, and tmeperature. This study shows that diffusion coefficient, D of 12% Cr rotor steel at 953K with 74.8 MPa is 1.084~3.140*$10^{15}mm^2sec^1$ compared to $1.658*10^{24}mm^2sec^1$at 963K without stress. During creep, the growth of martensite laths accelerates the diffusion coefficient under stress due to incoherency of interface between carbides and matrix.