実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report
課題番号 Project No. 2009B0009

提出日 Date of Report2010 年 月 日
装置責任者 Name of responsible person
Kazuya Aizawa

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）SCC crack propagation characteristics from Inconel to Engineering
low-alloyed steel

materials

diffractometer

BL-19

実験責任者名 Name of principal investigator
実施日 Date of Experiment

Yo Tomota
所属 Affiliation

May 25-26, 28 (net 3 days)

Ibaraki University

試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
Low alloy steel: 0.20C-0.24Si-1.42Mn-0.01P-0.006S-0.11Cu-0.64Ni-0.12Cr-0.54Mo-0.003V0.002Nb-0.001Ti (mass %) and Ni alloy: 68.90Ni-14.70Cr-7.23Fe-6.50Mn-1.55NbTa-1.50Nb-0.44Si0.053C-0.004P-0.002S (mass%)

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results. If you failed to conduct experiment as planned, please describe reasons.
To examine the SCC crack propagation from Ni alloy to low alloy steel, a welded component was preparedartificially. A compact tension specimen was made from this component and fatigue crack was introduced toreach near the weld interface. Trial was made to measure residual stress distribution near the weld interface
and at the crack tip of fatigue crack. The gauge volume for strain measurement was adjusted using 2mm
collimator in front of the detector and 2mm width slit for the incident beam. The measuring point was scannedas is illustrated in Fig. 1. Diffraction profiles were obtained from three orthogonal directions. The hkl lattice
distance was determined by curve fitting using the Gaussian function. So called stress-free spacing wasdetermined from coupons with 7x7x7mm for both Ni alloy and low alloy steel. The hkl lattice plane distancedetermined in each direction was converted to lattice constant (a) and the averaged a was calculated fromavailable hkl plane distances obtained. Similarly, stress free value (a0) was calculated for the data from thecoupons. Then, elastic strains were computed by (a- a0)/ a0. The stresses in three orthogonal directions werecalculated from the general Hooke law, where Young modulus was taken as 214 GPa for the low alloy steel,
200 GPa for the Ni alloy and Poisson ratio was 0.30 for the both materials.
The stresses along line AB in Fig. 1 determined are plotted in Fig. 2. As seen, tensile residual stresses arefound in the Ni alloy while compressive ones in the low alloy steel although some differences exist dependingon the direction. This result for the low alloy steel region shows good agreements with those predicted from12. 実験方法及び結果（つづき） Experimental method and results (continued)
the conventional X-ray method (on the surface) anddetermined by the angular dispersion neutron
diffraction using RESA at JRR-3. In case of RESA,
however, the stresses in the Ni alloy region could
not be measured because of texture (and coarsegrains). In this cases, the some hkl diffraction peaks
were obtained from any direction even though thespecimen is heavily textured. This is one of themerits to use the TOF method for stress evaluation.
The data obtained along the line CD were similar toFig. 2. Because the welded Ni alloy region shrinks
during solidification, tensile stresses along theinterface must remain while compressive stresses
in the low alloy steel region. Although thewelded specimen was subjected to stress-relief
annealing, it was revealed not enough to reduce
the residual stresses, which must affect theSCC crack growth behavior.
Theεxx andεzz at point C in Fig. 1(b) can beevaluated because the edge effect did notFig. 1 Experimental conditions for residualappear. In this case, the upper half space of thestress measurement for a welded component

gauge volume is occupied by Ni alloy, which
does not bring any artificial peak shift. To obtain

Inconel Low alloy steel

rotated by 180 degrees and the two diffraction
profiles before and after rotation should besummed. Such a trial will be made in future.
The CT specimen was loaded in tension andstrain measurement in front of crack tip wastried to measure. It is however the spaceresolution of 2x2x2 mm is not enough toevaluate the stress condition at the weldinterface.

Hence,SEM/EBSD

andothertechniques

synchrotron

500

X-ray

σx x
σyyσzz

400
300
200
100
0-10 0-4likemeasurement are planned to be performed
complementally.

Re sidual stres ses (M Pa)

ε ｙ ｙ at C, however, the sample has to be

0481216

Dis tance from the weld interface (mm)Fig. 2 Residual stress distribution along line
AB near the weld interface2