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Title: Novel Processing of mo-si-b Intermetallics for improved efficiency of power systems

Multiphase composite alloys based on the Mo-Si-B system are candidate materials for ultra-high temperature applications. In non load-bearing applications such as thermal barrier coatings or heat exchangers in fossil fuel burners, these materials may be ideally suited. Alloys based on the Mo{sub 5}Si{sub 3}B{sub x} phase (Tl phase) possess excellent oxidation resistance to at least 1600 C in synthetic air atmospheres. However, the ability of Tl-based alloys to resist aggressive combustion environments has not yet been determined. The present work seeks to investigate the resistance of these Mo-Si-B alloys to simulated combustion atmospheres. Material was pre-alloyed by combustion synthesis, and samples for testing were prepared by classic powder metallurgical processing techniques. Precursor material synthesized by self-heating-synthesis was sintered to densities exceeding 98% in an argon atmosphere at 1800 C. The approximate phase assemblage of the material was 57% Tl, 29% MoB, 14% MoSi{sub 2} (wt%). The alloy was oxidized from 1000-1100 C in flowing air containing water vapor at 18 Torr. At 1000 C the material achieved a steady state mass loss, and at 1100 C the material undergoes a steady state mass gain. The oxidation rate of these alloys in this temperature regime was accelerated by the presence ofmore » water vapor compared to oxidation in dry air. The results of microstructural analysis of the tested alloys will be discussed. Techniques and preliminary results for fabricating near-net-shaped parts will also be presented.« less
Authors:
; ; ;
Publication Date:
OSTI Identifier:
832908
Report Number(s):
IS-M 930
TRN: US200430%%989
DOE Contract Number:
W-7405-Eng-82
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 30 Sep 2004
Research Org:
Ames Laboratory, Ames, IA (US)
Sponsoring Org:
USDOE Office of Science (SC) (US)
Country of Publication:
United States
Language:
English
Subject:
24 POWER TRANSMISSION AND DISTRIBUTION; 29 ENERGY PLANNING, POLICY AND ECONOMY; ALLOYS; ARGON; BURNERS; COATINGS; COMBUSTION; EFFICIENCY; FOSSIL FUELS; HEAT EXCHANGERS; OXIDATION; POWER SYSTEMS; PRECURSOR; PROCESSING; SYNTHESIS; TESTING; THERMAL BARRIERS; WATER VAPOR