US005983982A [ii] Patent Number: 5,983,982  Date of Patent: Nov. 16,1999
 INVESTMENT CASTING WITH IMPROVED AS-CAST SURFACE FINISH
 Inventors: Joseph M. Vihtelic; Alan J. Graham, both of Whitehall; Robert L. McCormick; Laura A. Carpenter,
both of Muskegon, all of Mich.
 Assignee: Howmet Research Corporation, Whitehall, Mich.
 Appl. No.: 08/736,534  Filed: Oct. 24, 1996
 Int. CI.6 B22C 7/02; B22C 9/04
 U.S. CI 164/516; 106/38.8; 164/34;
164/35; 164/45; 164/235
 Field of Search 164/34, 35, 45,
164/516, 235; 106/38.6, 38.8
 References Cited
U.S. PATENT DOCUMENTS
5,185,108 2/1993 Shimandle .
5,270,360 12/1993 Solomon .
FOREIGN PATENT DOCUMENTS
50-7722 1/1975 Japan .
Metals Handbook, 9th Edition, vol. 7, pp. 25-29. Abstract of Japanese Patent Publication 57-187207 Published Nov. 17, 1982.
Primary Examiner—-J. Reed Batten, Jr.  ABSTRACT
The pattern material with substantially spherical filler particulates is used to produce investment cast components with improved surface quality, reduced finishing costs, and reduced core breakage. The pattern material comprises substantially spherical particles within the particle size range of about 10 microns to about 70 microns particle diameter, the use of which reduces the number of random, localized surface depressions and pits to improve pattern surface texture and uniformity. Patterns so formed inpart the same improvements to the surface of subsequent investment cast components. The resulting castings exhibit improved as-cast surface finish and reduced random, localized surface pitting, thereby reducing or eliminating expensive post casting surface finishing operations. Moreover, the spherical morphology of the filler particulates reduces injection pressures to fill a pattern die cavity as compared to non-spherical filler particulates. The lower injection pressures eliminate or reduce breakage of ceramic cores positioned in the die cavity for manufacture of hollow cast components, such as internally cooled turbine blades and vanes.
14 Claims, 4 Drawing Sheets