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Home  >  Journal list  >  Journal of the Society of Materials Science, Japan  >  Vol.64  No.2 (2015)  >  pp.94-99

Journal of the Society of Materials Science, Japan
<<Previous article Vol.64  No.2 (2015)   pp.94 - 99 Next article>>

EBSD Analysis of Grain Strain Distribution for Creep Damaged Modified 9Cr Steel

Kazunari FUJIYAMA1), Akihiro OGAWA2), Kazuma HARADA2), Hirohisa KIMACHI1)
1) Department of Mechanical Engineering, Faculty of Science and Technology, Meijo University 2) Graduate School of Science and Technology, Meijo University

Creep damage evaluation by EBSD(Electron BackScatter Diffraction pattern) method was conducted on the ferritic heat resistant Mod.9Cr steel as the turbine piping material. Creep damage was imposed under the condition of 600℃/130MPa and 650℃/100MPa with various interruption hours. The longitudinal mid-section of specimen was cut and observed by EBSD equipment and then Boundary maps, IPF(Inverse Pole Figure) maps, KAM(Kernel Average Misorientation) maps and GROD(Grain Reference Orientation Deviation) maps were obtained. Boundary maps showed the decreasing sub-boundary length having relatively small rotation angles with the increasing time fraction or the accumulated macroscopic creep strain. The misorientation parameters obtained from KAM maps and GROD maps showed decreasing trend with increasing time fraction. The distribution function of GROD was regressed on the basis of continuously distributed dislocation theory and its representative coefficient parameter AG showed good correlation with time fraction or accumulated creep strain. AG multiplied by equivalent grain diameter ld seemed to show slightly higher sensitivity to creep strains. A good correlation between the void length and the creep strain evaluated from AGld was observed. The AGld parameter was considered as an effective quantity obtained from EBSD observation to evaluate creep strain intensity at the grains with and without creep voids irrespectively.


Keyword:
Creep damage, Modified 9Cr steel, EBSD, Misorientation, Creep strain, Creep void, Dislocation

Received: July 14, 2014
Published online: February 20, 2015

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