Criteria for Design With Structural Materials in Combined-Cycle Applications Above 815°F

A number of materials issues related to the design of piping and support components in high-temperature fluidized bed combustor systems are examined. These issues include the availability of long-time design data on structural materials, the general character of the creep and stress rupture behavior, the performance of weldments, and the assessment of damage accumulation. Emphasis is placed on alloy 800H, but several other alloys were briefly examined for use at temperature above 816 C (1,500 F). The paper concludes that the character of the creep curve ranged significantly with chemistry, processing variables, and environment, and that the specification of design allowable stresses and life estimation techniques must be approached with caution for service above 816 C (1,500 F).