Particle impacts on the melt layer of an ablating body

tim rcquiretl lor an aluminum aircraft structure; the study extends to JL ~ 10, height of rgo,ooo feet, and a range of 5,000 miles. A

Technical Sot? Ll-64 Januar? lybi. LO pp. OTS price, $0.75. The rates of weight loss for silicon carbide, graphite, nylon, Hakclite, Fiberglas phenolic. and ammonium chloride have been invcstigated as a function of oxygen concentration and radiant heat flux. The investigation was made with an arc-image furnaw which provides radiant heat fluxes in the range of loo to 1,000 I3.Th.I!. ft.“-sec. In the upper half of this range the rate-controlling process for materials that oxidize was found to bc the diffusion rate of oxygen to the specimen surfaw

Particle Impacts on the Melt Layer of an Ablating Body. E. TV. Crngar. ,I. AWZ. Hock&. SW, jw (Sept. J960) 7’19~X05. An equation is developed relating the increase in erosion rate, as a result of partick impacts, to flight and material parameters. The ctxtcnt of the melt layer protection was found to be dependent on the particle size and melt layer thickness. One experimental check on the analysis was possible by inspection of the order of magnitude of the experimental liquid melt layer thickness on fired Micarta specimens. The computed melt layer thickness agreed with that observed on glass-reinforced Micarta 259-2 test specimens which were exposed in a rocket exhaust jet. High-Temperature Bearing Properties and Cobalt-Base Alloys. 11. F. Amateau. Cobalt, (9) (l>cc. 1960) 27-33. The specific requirements of high-temperature bearing properties seem to be met by cobalt alklys. \;\Thatseems to be lacking is a systcmatlc investigation of the various hightemperature cobalt-base alloys under actual bearing conditions. There is also little mcntion in the literature of de\~clopmcnt of cobalt-base alloys specifically for high-tcmperature bearing UC. On the basis of the present literature survey, there arc strong indications that cobalt-base alloys may be developed into bearing materials having outstanding properties. Development of Iron-Base Seal Materials for High Temperature Applications. Robert J. MacI>onald. ASLE P~pev ,‘VVII.60 L&II, Oct. 1960, I 8; 8 figs. This paper describes an experimental investigation of materials for use as high temperature rubbing seals. The results of a comprehensive evaluation of

‘fhcsc comrncrcial tool stcelh are not ~II~c.tivc cover’ looo”l~~; thcrcfore, n~%wmaterial \vcw sought. (Ising po\vdc~combinations Inekdllurgy techniques, a series of iron-base, alloys containing molybdenum and cobalt \vas studied It was found that alloys containing from 5 to 101);) of both n~c~l~bdenurn and cobalt exhibit excellent rubbing propcrtics up to 1 roo’F, and in general, XI’ supcri~z to the tool steels tested Further testing of 1:~ MO (‘0 materials revealed that friction and \vcar are markedl) dependent upon the test conditions. .\ minimum coefficient of friction was obtained with the highest surfaw spwd (150 ft./see) and with the highest ambient tcmpcrature

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The desirable rubbing propcrtics ot this family of materials arc explained in terms of surface oxidation products which act as solid-film lubricants during high temperature rnbbing. Characteristics Governing the Friction and Wear Behavior of Refractory Materials for High-Temperature Seals and Bearings. Lewis 13. Sibley, :\rthur E. Mace, Ilaniel Ii. Grieser, and C. Malcolm .-2llen. (U.S. XrForce, \\:right .%ir I>evelopment I>ivision) IV.4 nn Tcch~tical l0~‘s, where p is the coefficient of friction, I? is the thermal-stress-resistance factor, and 1) is the thermal diffusivity of the material on which which is usually the wear predominates, material with the lowest thermal-stress resistance. Promising commercial materials for high-temperature dry sliding bearings, gas bearings, and seals include &O-Cr-Mo ccrmeti, Sic‘ ceramics, and Tic‘ Xi--%) cermets. Friction and Wear of Metals in Gases up to 600°C. 11. E? Comchus and \I;. H. Roberts. ,4SI_E paper No. 60 IX-(), Oct. 1960, 1-13; rh figs., 1 tables, LO refs.