X-Ray Residual Stress Measurement on Weld Metal of Nickel Based Alloy
Koichi AKITA, Yasuo YOSHIOKA, Yuji SANO, Kazuo OGAWA, Tatsuya KUBO, Minoru OBATA and Hirotomo TANAKA
Abstract:Residual stress on the weld metal of nickel based alloy was evaluated through x-ray diffraction and metallurgical study of the microstructure. Weld metal specimens were prepared from Alloy182 (JIS DNiCrFe-3) and Alloy132 (JIS DNiCrFe-1J) deposited on a steel plate. X-ray diffraction results show a strong [100] preferred orientation nearly normal to the surface of the weld metal. Crystallographic consideration predicts that dominant 311 diffractions appear around 25.2 and 72.5 degrees of ƒÕ angle. For each diffraction, the peak shift was measured at the ƒÕ angle showing the maximum diffraction intensity, using the side-inclination method (ƒÕ -goniometer method) with a Mn x-ray tube and a PSPC (position sensitive proportional counter). The residual stress was determined by the peak shifts according to the two tilt method. The x-ray stress constant, K, on Alloy 182 was determined experimentally. The depth profile of the residual stress was measured on the ground specimens with and without laser peening. Tensile residual stress due to the grinding work is observed in the surface layer of the unpeened specimen; however it changes to compressive after laser peening. The overall behavior of the depth profile of laser peened material agrees well with that of Alloy600 base metal measured in the previous studies, where the compressive residual stress with several hundred Mpa at the surface gradually decreases and reaches to around 0 Mpa at the depth of about 1 mm. Key Words:Nickel based alloy, Weld metal, Preferred orientation, X-ray, Stress measurement, Laser peening