Weldability of EPRI P87

摘要

Dissimilar metal welds (DMWs) between ferritic and austenitic materials at elevated temperatures have concerned boiler manufacturers and operators for decades because of the proven potential for premature failure. With the current trend toward ever higher pressures and temperatures to achieve increased boiler efficiencies, it would be advantageous to have a superior weld metal and joint design that would optimize economy of the newer boilers and help avoid the use of austenitic materials for steam headers and piping. EPRI has developed a new filler metal to improve the performance of DMWs, EPRI P87. Previously, work has been reported on the development of EPRI P87 shielded metal arc welding electrode, gas-tungsten arc welding fine-wire, and the utilization of EPRI P87 in an ultra-supercritical steam boiler built and constructed by B&W. This paper discusses the weldability of EPRI P87 consumables using various test methods such as varestraint testing (trans and spot), long-term creep testing (~10,000 hour running tests), procedure qualification records of tube to tube weldments between traditional/ advanced austenitics and creep-strength enhanced ferritic steels, and elevated temperature tensile testing. Finally, macros taken from the procedure qualification records were examined using light microscopy to verify the weldability and elimination of cracking between all possible material combinations. All these data show EPRI P87 is a weldable alloy which has a number of advantages for use in DMW applications. The data also show that for specific weld joint configurations, procedure qualifications may require the use of high-temperature tensile data.