UNS(1) N06055 alloy has been evaluated for resistance to primary water stress corrosion cracking (PWSCC), ductility dip cracking (DDC), and solidification cracking (hot-cracking). Metallurgical stability after exposure to temperatures above nuclear operating temperatures has been evaluated by x-ray diffraction by the Ohio State University (OSU)(2) and KAPL (Knolls Atomic Power Laboratory)(3). Additional mechanical properties have been predicted and compared to values measured from a weldment, and are reported after post weld heat treatment at 621°C (1150°F) for 48 hours. New applications for which this product is being evaluated include: J-welds for control rod drive mechanisms (CRDM), pressurizer nozzles, thick section buttering to facilitate safe ending, laser welded inlays, and overlays. This paper summarizes and reports useful properties and new data for this product. New PWSCC testing is planned for specimens that have been exposed to 1150°F 621 °C (1150°F) for 48hours. Also, an additional longitudinal varestraint testing program is in progress. Further data is expected from a third production melt of UNS N06055 alloy that will be used for complete qualification of weldstrip overlays as well as additional wire testing. High temperature tensile testing is being completed to further define the capabilities of UNS N06055 alloy. Also rigorous qualification testing to rigid standards is being completed for structural weld overlay applications and additional strain-to-fracture (STF) testing has revealed an increase in threshold strain value for UNS N06055 alloy that reaches 27-28% threshold strain.

Subject
Test methods, Crack growth, Materials, Nuclear power, Nickel based alloys, Molybdenum alloys, Welding, Solidification, Stress cracking, Commercial alloys, Grain boundary, Alloys, Yield strength
Keywords:
UNS N06055 alloy, Strength, PWSCC, DDC, Hot-Cracking, Corrosion, Nickel Alloy
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2014
Association for Materials Protection and Performance (AMPP)
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