Sulfidation-Resistant Alloy/Cladding for Internal Components of Coal-Conversion Equipment. Volume 2. Cladding Development. Final Report

摘要

An Fe-19Cr-8Al-0.5Hf alloy has been roll bonded to Alloy 800 to form a protective clad material suitable for use in coal conversion atmospheres. The commercial producibility of both the Fe-19Cr-8Al-0.5Hf alloy and the clad composite has been demonstrated. The clad composite has been shown to exhibit resistance to sulfidation in high sulfur, coal gasification atmospheres low Btu for 2000 hrs at 1800 exp 0 F (1255K). The FeCrAlHf alloy must be preoxidized in the absence of sulfur to form fully protective alumina scales on all surfaces. Useful life of the composite at temperatures of 1400 to 2000 exp 0 F (1033 to 1366K) is governed by reactions at the FeCrAlHf clad alloy 800 interface. The rate of interdiffusion decreases with increasing Ni content and a high Ni alloy such as RA333 appears to be a better substrate than Alloy 800 for a FeCrAlHf composite. The mechanical properties of the clad composite have been evaluated at both ambient (tensile and bend) and elevated (tensile and creep rupture) temperatures both in the as-roll-bonded condition and after a variety of thermal and corrosion exposures. The FeCrAlHf alloy is embrittled by grain growth on long time exposure above 1500 exp 0 F(1089K) in either air or gasification atmospheres. Ductility of the composite and clad composite interface is both reduced by the interdiffusion of Al and Ni. The FeCrAlHf alloy as presently formulated cracks on welding and further work is needed to develop effective joining and weld overlay procedures. A FeCrAlHf clad composite has good potential as a low-cost, non-strategic material for broad use in coal gasification atmospheres and continuing research including scale up to pilot plant testing is recommended. (ERA citation 07:050842)