Abstract
This paper is a research output of DMW-Creep project which is part of a national UK programme through the RCUK Energy programme and India's Department of Atomic Energy. The research is focussed on understanding the characteristics of welded joints between austenitic stainless steel and ferritic steel that are widely used in many nuclear power generating plants and petrochemical industries as well as conventional coal and gas-fired power systems. The members of the DMW-Creep project have undertaken parallel round robin activities measuring the residual stresses generated by a dissimilar metal weld (DMW) between AISI 316L(N) austenitic stainless steel and P91 ferritic-martensitic steel. Electron beam (EB) welding was employed to produce a single bead weld on a plate specimen and an additional smoothing pass (known cosmetic pass) was then introduced using a defocused beam. The welding residual stresses have been measured by five experimental methods including (I) neutron diffraction (ND), (II) X-Ray diffraction (XRD), (III) contour method (CM), (IV) incremental deep hole drilling (iDHD) and (V) incremental centre hole drilling (iCHD). The round robin measurements of weld residual stresses are compared in order to characterise surface and sub-surface residual stresses comprehensively.
Highlights
The dissimilar metal weld (DMW)-Creep project is part of an international scientific collaboration between the UK research councils and India's Department of Atomic Energy
In addition to this divergence measured at the weld centreline, there are at least three points indicating an obvious measurement error as the RS reaches 900 MPa which is much higher than the yield strength of AISI 316L(N)
A recent electron back scattering diffraction (EBSD) analysis of the weld fusion zone by Abburi Venkata et al [43] showed that segregation of face-centered cubic (FCC) and body-centered cubic (BCC) phases in the cosmetic pass region is consistent with the observations from neutron diffraction results
Summary
DMW-creep is focussed on understanding the characteristics of electron beam (EB) welded joints between austenitic stainless steel (AISI Type 316LN) and ferritic-martensitic steel (P91). The AISI 316L(N) stainless steel has a thermal conductivity of one-half of P91 while the coefficient of thermal expansion is 45% greater than P91 These mismatches in material properties result in differing stress profiles on either side of the weld. Kerr et al [20] conducted a combination of neutron diffraction, contour method, and hole drilling residual stress measurements on a DMW plate specimen, fabricated from a 304L stainless steel plate and Nickel Alloy 82 weld, and compared the experimental measurements to a finite element weld modelling results.
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