Ultrasupercritical (USC) steam boiler and heat recovery steam generator (HRSG) technology is constantly evolving to improve efficiency and reduce emissions. Currently, temperatures are pushing beyond the capabilities of even the most advanced ferritic steels with some applications requiring nickel-based superalloys. Cost-effective design of these systems requires the application of a variety of alloys representing a range of cost/property trade-offs. CF8C-Plus is a cast austenitic stainless steel recently developed for application in high temperatures similar to those in power plants (600 - 900 °C) with creep strength comparable to several superalloys. This makes it an attractive alternative for those expensive alloys. EPRI, with assistance from PCC subsidiaries Special Metals and Wyman Gordon Pipes and Fittings, has produced and characterized two pipe extrusions nominally 5.25 inch OD x 0.5 inch wall thickness and 6 inch OD x 0.75 inch wall (13.3 x 1.3 cm and 15.2 x 1.9 cm), each about 1000 lbs, to continue to assess the feasibility of using a wrought version of the alloy in power piping and tubing applications. The mechanical properties from these extrusions show performance in the same population as earlier forging trials demonstrating capability exceeding several austenitic stainless steels common to the industry. Creep-rupture performance in these extrusions continues to be competitive with nickel-based superalloys.

This content is only available as a PDF.