Exhaustive testing has been conducted and reported previously on UNS N06055 in corrosion 2014 paper number 4223. These data support the use of UNS N06055 for nuclear applications where resistance-to-cracking during fabrication and resistance to primary water stress corrosion cracking (PWSCC) in service are of paramount importance. Additional data are being developed to define PWSCC crack growth rates (CGR) after typical post-weld heat treatment (PWHT) procedures which may reach a total of 48 hours at 1130 degrees F. Also, high temperature tensile tests have been conducted that show welds made with UNS N06055 are suitable for extended service lives at pressurized water reactor (PWR) nuclear operating temperatures.
Work is continuing on investigating solidification cracking tendencies and the effects of chemical composition, dilution, and secondary phases formed as a result of dilution. Finally, a direct comparison has been characterized by a third party nuclear repair company between UNS N06055 and N06054 when the latter was attempted to be qualified for a European structural weld overlay (SWOL) application. The discussion highlights the detailed light optical microscope (LOM) investigative result of welds made with each product as well as all weld metal mechanical properties in the “Z” direction for UNS N06055 when welded using the ambient temperature temper bead procedure.
Key Words: downloadable, UNS N06055, strength, PWSCC, solidification cracking, DDC, crack growth rate (CGR), nickel alloy, tensile strength