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The DOE/OCDO sponsored Ultrasupercritical Steam Boiler Consortium is conducting thermal shock tests on austenitic and nickel-based materials to assess their use in thick-section boiler components. This paper describes the tests on CCA617 (a controlled chemistry version of IN617) and Super 304H thick-walled tubes. Details are given of the metallurgical analyses of the observed cracking in the bore and on the outside diameter of the samples, and of the thermal-mechanical analyses to explain the results. Elastic-plastic and elastic-plastic-creep analyses are used to calculate damage based on rupture life and creep strain accumulation. The results of the metallurgical and mechanical analyses are compared, and conclusions are drawn as to the accuracy and effectiveness of available high temperature life prediction techniques. The test conditions bear no relation to expected operating conditions. They are chosen to generate failure data. [DOI: 10.1115/1.3120265]

The Oak Ridge National Laboratory (ORNL) and ATI Allegheny Ludlum worked together on a collaborative program for about two years to produce a wide range of commercial sheets and foils of the new AL20-25+Nb[TM] (AL20-25+Nb) stainless alloy for advanced microturbine recuperator applications. There is a need for cost-effective sheets/foils with more performance and reliability at 650-750[degrees]C than 347 stainless steel, particularly for larger 200-250 kW microturbines. Phase 1 of this collaborative program produced the sheets and foils needed for manufacturing brazed plated-fin air cells, while Phase 2 provided foils for primary surface air cells, and did experiments on modified processing designed to change the microstructure of sheets and foils for improved creep-resistance. Phase 1 sheets and foils of AL20-25+Nb have much more creep-resistance than 347 steel at 700-750[degrees]C, and those foils are slightly stronger than HR120 and HR230. Results for Phase 2 showed nearly double the creep-rupture life of sheets at 750[degrees]C/100 MPa, and similar improvements in foils. Creep data show that Phase 2 foils of AL20-25+Nb alloy have creep resistance approaching that of alloy 625 foils. Testing at about 750[degrees]C in flowing turbine exhaust gas for 500 h in the ORNL Recuperator Test Facility shows that foils of AL20-25+Nb alloy have oxidation-resistance similar to HR120 alloy and much better than 347 steel. [DOI: 10.1115/1.2718569]

Superheaters (SH) and reheaters (RH) in modern supercritical (SC) and ultra supercritical (USC) coal-fired steam power plants operate with maximum steam temperatures between 580 and 620°C and pressures up to [...]

Abstract: Creep–rupture experiments were conducted on multiple heats of the nickel-based superalloy Inconel® 740 at temperatures between 923 and 1123K (650 and 850°C). The interactions between chemistry, microstructure, and creep performance were evaluated by analysis of creep data, optical microscopy, electron microscopy, and computational thermodynamics. The data show that grain size has a modest effect on the creep–rupture strength. Computational thermodynamics verified experimental observations of the formation of eta phase as a function of temperature and alloy chemistry, but the kinetics for the precipitation of eta phase did not agree with the experimental findings. Despite the formation of eta phase and the concomitant reduction in volume fraction of gamma prime, the creep resistance of the alloy is insensitive, within the range of chemistries tested, to the volume fraction of gamma prime. The creep ductility was found to increase with test temperature. Precipitation of a large volume fraction of eta phase (greater than 7%) appears to reduce the creep–rupture ductility, but smaller amounts do not produce adverse effects. [Copyright &y& Elsevier]