Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
1999-03-26
2002-04-23
Jenkins, Daniel J. (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C075S246000, C419S002000, C419S019000, C419S029000, C419S042000, C419S060000
Reexamination Certificate
active
06375705
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to alloys for use in high temperature, corrosive environments. More particularly, it relates to alloys and porous metal filters and other less-than-fully dense components made from the alloys.
2. Description of the Prior Art
Pressurized fluidized bed combustion (PFBC) systems and integrated gasification combined cycle (IGCC) systems offer high efficiency methods for extracting energy from fossil fuels. Both systems operate at high temperatures and produce a high temperature gas which contains particulates and corrosive gases. Systems under development are expected to require filters operational in the range of 400-930° C. (750-1700° F.). Ceramic filters are susceptible to failure especially at the higher temperatures due to poor resistance to thermal and mechanical shock. Porous sintered metal filters offer an alternative to ceramics if corrosion resistance can be obtained in a sufficiently ductile material to be readily fabricated.
Full density iron aluminides have been known since 1930 [Sykes et al.,
J. Iron and Steel Inst.,
130, 389 (1930)]. The excellent corrosion resistance, comparatively low density low cost and tensile strengths make them a favorable alternative to ferritic and austenitic steels. Unfortunately, the ductility of the alloys at room temperature makes them difficult to fabricate and their reduced strength at temperatures over 600° C. has limited their use in hot corrosive atmospheres.
Adjustments to the ratio of Fe to Al and the addition of minor amounts of other metals have resulted in improved ductility and tensile yield strengths. See U.S. Pat. Nos. 4,961,903, 5,084,109, 5,238,635 and 5,320,802.
Less-than-full-density iron aluminide filters fabricated using powdered metal technology (hereinafter “sintered metal filters”) have been fabricated and subjected to initial testing [Judkins et al., Proceedings of the Advanced Coal-Fired Power Systems '96 Review Meeting< DOE, Morgantown W. Va. 1996]. The sintered metal filters have improved corrosion resistance compared to SS 316 and 310 sintered filters but strength at temperatures above 700° C. is insufficient.
There remains a need for sintered metal filters which are stable and operable at temperatures above 700° C., preferably above 800° C. in both oxidizing and reducing atmospheres.
BRIEF SUMMARY OF THE INVENTION
It is an object of this invention to provide a sintered metal filter having improved corrosion resistance at temperatures above 700° C.
It is an object of this invention to provide a sintered metal filter having increased tensile strength at temperatures above 700° C. It is a further object of this invention to provide a sintered metal filter with improved creep resistance.
These and other objects of this invention may be obtained by the addition of an oxide-dispersion strengthening component to the alloy powder prior to fabrication and by heat treating the sintered filter to enhance grain growth.
REFERENCES:
patent: 4961903 (1990-10-01), McKamey et al.
patent: 5084109 (1992-01-01), Sikka
patent: 5238645 (1993-08-01), Sikka et al.
patent: 5320802 (1994-06-01), Liu et al.
patent: 5545373 (1996-08-01), Maziasz et al.
patent: 5637819 (1997-06-01), Schneibel
patent: 5976458 (1999-11-01), Sikka et al.
patent: 6033623 (2000-03-01), Deavi et al.
Hurley et al., “Iron Aluminide Hot Gas Filters”,Proc. Advanced Coal-Fired Power Systems, '96 Review Meeting, DOE Fed. Energy Tech. Ctr., Morgantown, W.V. 1996.*
Judkins et al. “Metal Filter Materials in Combustion Environments”,Proc. Advanced Coal-Fired Power Systems '96 Review Meeting, DOE, Fed. Energy Tech. Ctr., Morgantown W.V. 1996.
Jenkins Daniel J.
Nexsen Pruet Jacobs & Pollard LLC
O'Toole J. Herbert
U. T. Battelle, LLC
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