51312-01743-New 30% Cr Welding Product Provides Outstanding Resistance to Ductility Dip Cracking (DDC) And Meets

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Product Number: 51312-01743-SG

ISBN: 01743 2012 CP

Author: Samuel Kiser

Publication Date: 2012

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AbstractWeldments in vessels and components for nuclear power generation must be of especially high quality due to the complexity and criticality of this demanding service. Nickel-based products have been used from the outset of the nuclear industry due to their corrosion resistance. From the 1950’s to the 1980’s the 15%Cr to 20%Cr welding products were used until their susceptibility to primary water stress corrosion cracking (PWSCC) was discovered. 30%Cr-containing alloys and welding products (NiCrFe-7) were invented and used from the 1980’s and in the early 1990’s DDC was encountered during fabrication. In 1993 a more resistant set of products were introduced that had improved DDC resistance (NiCrFe-7A) and met PWSCC requirements. These products were and are being used successfully for the mitigation of PWSCC-susceptible materials in existing nuclear plants in the form of structural weld overlays (SWOL’s) and pre-emptive weld overlays (PWOL’s). As fabrication of new plant and equipment and larger overlays were needed greater resistance to DDC is being required. Therefore a new NiCrFe product was introduced that contained higher Nb and an addition of Mo (NiCrFe-13) that provides over 4x higher DDC resistance than any of the currently available competitive products. The Strain-to-Fracture (STF) test developed by the Ohio State University (OSU) has accurately measured the threshold strain to cause DDC in this product to be greater than 16% at 950C. In addition transvarestraint testing at OSU and PWSCC testing at the Pacific Northwest National Laboratory (PNNL) show excellent weldability and corrosion resistance. The product is characterized by UNS N06055 AWS A5.14 ERNiCrFe-13 and ASME Code Case 2142-3 and is currently commercially available. This paper presents the outstanding attributes of ERNiCrFe-13.