3/16-inch diameter. of Raney nickel inside. The second cylinder, B, is similar but the Raney nickel coating has been increased to 0.125 inch. The third cylinder, C, has the coating on the outside while the fourth cylinder, D, contains three tubes. Stainless steel tubes were incorpo rated because activated Raney nickel would be coralloid and not capable of supporting its own weight. Figure 13 is a photomicrograph of the end section of a swaging containing Raney nickel powder inside and aluminum outside. This was produced by compacting the powder at 207 MN/m then inserting it into a 1-inch-diameter tube and swaging the composite to Overall composition, aluminum sheath plus powder, is closer to the desired alloy composition (42 pct Ni-58 pct A1) than the commercial powders obtained. This is acceptable feed stock for thermally spray ing the catalyst. Without the initial compacting step swaging ruptured the sheath. CONCLUSIONS Commerand Raney nickel alloy has been found to be amenable to powder metallurgy processing despite being primarily a brittle intermetallic compound. cial powder was found to be a mixture of three phases: NiAl ̧, Ni¿Al ̧, eutectic. The powder is extremely angular and probably prepared by crushing a cast metal. Two sizes of powder were studied with similar angular shape. This angular shape, coupled with the aluminum present in the eutectic phase, does allow the alloy to be compacted with excellent green strength. Samples compacted at pressures as low as 34.5 MN/m have adequate green strength for normal handling. and decrease the porosity. Increasing the compacting pressure to 207 MN/m2 does increase the density nominal composition and this variation does cause a difference in compacted The commercial powder was found to vary from the and sintered density. With increasing aluminum content, more eutectic is present with its inherent ductility, allowing greater densification. Sintering has a profound effect on the density. A solid state reaction occurs between the Al and Ni2Al ̧ phases causing a volume expansion with a resulting decrease in density. This expansion was found to be as much as 30 pct. Com This volume expansion was eliminated by heating the powder to 700° C for 70 hours, the time and temperature for a complete solid state reaction. pacting and sintering can then be accomplished with an increase in density and decrease in porosity. treated powder. The final density however is less than for the nonheat Shapes of Raney nickel, made by powder metallurgy techniques, are feasible. Further research in the field of activation and catalytic activity are required to prove the value of powder metallurgy-produced Raney nickel catalysts. 1. 2. 3. 4. REFERENCES4 Fasman, A. B., V. F. Timofeeva, V. N. Rechkin, Yu. F. Klyuchnikov, and Forney, A. J. The Synthane Process. From the Materials Problems and Research Opportunities in Coal Conversion Work Shop sponsored by the National Science Foundation (NSF) and Office of Coal Research (OCR), Columbus, Ohio, Apr. 16-18, 1974. Itin, V. I., Yu S. Nayborodenko, and V. P. Ushakov. U.S. Pat. 1,628,190, 4 Titles enclosed in parentheses are translations from the language in which the item was published. INT.-BU.OF MINES, PGH., PA. 21608 ✩U.S. GOVERNMENT PRINTING OFFICE: 1976-603-755/168 |