• Huotilainen, Caitlin
• Keinänen, Heikki
• Virkkunen, Iikka
• Bhusare, Suprit
• Nevasmaa, Pekka
• Hytönen, Noora
• Kuutti, Juha
• Mohanty, Gaurav
• Lambai, Aloshious

Abstract

As nuclear power plants age and their lifetimes are being extended, the possibility and need to perform repairs of safety critical and hard to replace components is ever increasing. For example, defects in the reactor pressure vessel caused by exposure to high temperature, pressure, and corrosive environment together with neutron irradiation are often repaired by different repair welding techniques. Moreover, the need for such repairs may come at short notice requiring that qualified and optimized techniques and solutions are readily available. Developments of repair welding techniques using robotized gas metal arc welding cold metal transfer to repair a linear crack like defect beneath the cladding, which extended into the reactor pressure vessel steel have been presented in previous works [8-9]). In the latest piece of research [10], the repair welding of a thermally embrittled and cladded low-alloy steel plate with two groove excavations filled using Alloy 52 was presented. In the paper, the two welds were characterized with micrographs and microhardness measurements. This work further evaluates in more detail the differences and similarities of the repair welds welded using two different welding directions, 0-degree and 45-degree, and corresponding bead patterns. Residual stresses were measured from the two repair-weld cases using the contour method. Despite significant differences in the weld bead order and consequent welding procedure, the resulting residual stresses were very similar. It was expected that the crisscross weld bead pattern would cause the subsequent weld layers to induce stresses counteracting the previous layer and thus reduce the overall residual stress field. However, this does not appear to be the case. Both weld areas showed tensile stresses around 300 MPa, which is close to the yield stress of the weld material. Balancing compressive stress is induced to the base material with somewhat lower magnitude, peaking around 200 MPa. This indicates that the main determinant of the residual ...

Topics

• impedance spectroscopy
• corrosion
• chromium
• simulation
• crack
• steel
• hardness
• nanoindentation
• electron backscatter diffraction
• void
• porosity
• spectrometry
• elemental analysis
• tempering