The High Earth Orbit Space Surveillance Mission
- Paper number
IAC-04-IAA.5.12.1.02
- Author
Mr. Brad Wallace, Defence R&D Canada (DRDC), Canada
- Year
2004
- Abstract
Superalloys are multicomponent alloys where Ni or Co is a main component and Nb, W, Mo, Cr, V, Ti, Al, C, Si are alloying ones. The basic advantages of the products or coatings on their basis are high operational characteristics. The main criterions determining the quality of the multicomponent alloys are their correspondence to chemical composition, uniform component distribution in the alloy (absence of local nonuniformity), and fine grain size structure. Conditionally the work may be separated on two parts: first one is developing a new centrifugal technology for obtaining heat-resistant materials (superalloys) by self propagation high temperature synthesis (SHS) so called as combustion synthesis (CS); second one is investigation of ability of obtaining of cast intermetallic compounds (as basis of superalloys) under microgravity. Our approach consists in realization of high temperature in the combustion wave (higher than the melting points of the products) that leads to formation of the reaction products melt. Metal oxides, nonmetals and reducing agents are used as the initial materials of the exothermic process. The chemical scheme can be presented as follows:
(M1 + M2 + M3 + ...Mn) + (N1 + N2 + ...Nn) + R+Fadd ->[Multicomponent alloys] +Al2O3+Q, where: Mn –Cr, Ni, Co, Nb, W, Mo, Ti, etc. oxides, Nn – nonmetal Si, C, B, etc., R – reducing metal (Al), Fadd – functional additions.
The studies in conditions of centrifugation have demonstrated a strong influence of gravity conditions on all stages of SHS: combustion, formation of chemical/phase composition, and on the macro/microstructure of combustion products. SHS alloys obtained by SHS metallurgy have unique microstructure high higher heterogeneity. The size of structural components is 10 times lower and has nano-size inclusions. A decrease in grain size is caused by SHS conditions: first of all, it is high synthesis temperatures (about 25000C in comparison with 18000C realized in electric furnaces) and higher cooling rate. The effect of high gravity leads to the uniformity of chemical composition in the ingots and a decrease in structural components size. The basic difference of the approach from the conventional vacuum electrometallurgy is realization of high temperatures without using any additional power sources. The circumstance makes advantages of using the technique for obtaining such materials under microgravity conditions (on space vehicle). Space experiments which we performed aboard the International Space Station has demonstrated ability obtaining of cast intermetallic compounds (based on Ni-Al). Our data imply that the ground technique may be convey to space for space vehicle requirements or also used as impact heat generator for high temperature experiments.
The work was carried out under financial support of RFBR, grant no. 06-03-32188, and Russian Space Agency and ENERGIA Rocket and Space Corp.
- Abstract document
- Manuscript document
IAC-04-IAA.5.12.1.02.pdf (🔒 authorized access only).
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