Weld residual stresses near the bimetallic interface in clad RPV steel: A comparison between deep-hole drilling and neutron diffraction data

Abstract

The inner surface of ferritic steel reactor pressure vessels (RPV) is clad with strip welded austenitic stainless steel primarily to increase the long-term corrosion resistance of the ferritic vessel. The strip welding process used in the cladding operation induces significant residual stresses in the clad layer and in the RPV steel substrate, arising both from the thermal cycle and from the very different thermal and mechanical properties of the austenitic clad layer and the ferritic RPV steel This work measures residual stresses using the deep hole drilling (DHD) and neutron diffraction (ND) techniques and compares residual stress data obtained by the two methods in a stainless clad coupon of A533B Class 2 steel. The results give confidence that both techniques are capable of assessing the trends in residual stresses, and their magnitudes. Significant differences are that the ND data shows greater values of the tensile stress peaks (~100 MPa) than the DHD data but has a higher systematic error associated with it. The stress peaks are sharper with the ND technique and also differ in spatial position by around 1 mm compared with the DHD technique.

Redistribution of residual stress by thermal shock in reactor pressure vessel steel clad with nickel alloy

“…Residual stress measurements presented in this paper were carried out on 42 mm (post-weld heat-treated) and 58 mm (as-welded) thick plates, whereas RPVs have much thicker walls, typically around 180 -200 mm. Measurements in previous work by James et al [9] showed that the residual stress in a clad plate was significantly affected by reducing the thickness of the plate from 80 mm to 30 mm. Rybicki et al [36] extracted 32 mm thick samples from a larger clad plate, and found that reducing the thickness of the cladding by half from 8.9 to 4.4 mm significantly increased the magnitude of residual stress in the cladding.…”

“…However, the residual stress is not completely erased [2][3][4] because additional stresses are generated upon cooling due to the difference in thermal expansion coefficient between the cladding and parent materials. The residual stress in pressure vessel steel clad with stainless steel has been well characterised in previous work using modelling techniques [2,4] and experimental measurements [2][3][4][5][6][7][8][9][10]. In general, material which has been post-weld heat-treated contains high tensile residual stress in the cladding of around 200 -400 MPa, and lower-magnitude tensile or compressive stress in the parent [3,7,11].…”

Effect of cutting parameters on surface residual stresses in dry turning of AISI 1035 alloy

“…Many attempts have been done to figure out the relationship between different cutting parameters/conditions and the induced RSes using experimental [6][7][8], analytical modeling [9][10][11], finite element modeling [12][13][14], and various combinations of them [15][16][17] in various machining operations [18][19][20]. The experimental investigations were carried out via measuring the RSes using different measuring methods such as ring core method [21], hole drilling technique [22], deep-hole drilling [23], slope cutting method [24], contour method [25], synchrotron diffraction [26] method, XRD method [27], and neutron diffraction method [28]. Among all these measuring techniques, XRD and hole drilling technique are the most commonly used in machining applications.…”