Quantitative Residual Strain Analyses on Strain Hardened Nickel Based Alloy

Abstract

Many papers have reported about the effects of strain hardening by cold rolling, grinding, welding, etc. on stress corrosion cracking susceptibility of nickel based alloys and austenitic stainless steels for LWR pipings and components. But, the residual strain value due to cold rolling, grinding, welding, etc. is not so quantitatively evaluated.

Therefore, authors quantitatively measured and evaluated the residual strain value for strain hardened tensile or torsion specimens of nickel based alloys by applied strain, FWHM of gamma X-ray diffraction, EBSD and Vickers’ hardness measurement to make a calibration curve, at first. Using these curves, the residual strain in the heat affected zone of weld joint and cold worked plates, etc., was quantitatively evaluated from the measuring data of Vickers’ hardness or EBSD or FWHM of gamma peak in X-ray diffraction. As a result, residual strain value in the heat affected zone of weld joint was evaluated as about 10% of von Mises equivalent strain from FWHM, EBSD and Vickers’ hardness measurement. But the residual strain of the 20% and 30 % cold rolled Alloy 600 or TT690 were evaluated about 40% and 60 % of von Mises equivalent strain, respectively.