Howmet Research Corporation

Dow Global Technolgoies LLC

Howmet Corporation

Joseph M Vihtelic

Yunwa Wilson Cheung

Charles F Diehl

Dane Chang

Alan J Graham

Robert L McCormick

Laura A Carpenter

Kurt C Frisch

Jiri E Kresta

Philip D Jackson

A fugitive pattern for making a shell mold for investment casting a metal or alloy comprises a substantially random interpolymer and a low molecular weight polymer in proportions to provide a fugitive pattern having a combination of properties suitable for use in making the shell molds.

Fugitive pattern for casting

An investment casting method using a 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 impart 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.

Investment casting with improved as-cast surface finish

Method of making a shell mold for casting molten metals or alloys involves forming a thermally collapsible, low density reaction injection molded (RIM) thermosetting polyurethane foam pattern having a shape corresponding to the casting to be made. The pattern is formulated to have an aggregate density (pattern outer skin and pattern cellular core) in the range of about 10 to 15 lbs/ft and a smooth continuous as-molded surface devoid of surface connected open cells, dimensional stability over a range of temperatures, and ready, ashless burnout from the shell mold formed thereon without cracking the shell mold. The pattern is free of organometallic catalysts that should not be present in the casting of aerospace superalloys, such as nickel and cobalt base superalloys and titanium. The pattern then is invested without the need for any surface polymer or other film or layer in a shell mold.

Investment casting patterns and method

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.

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Whitehall, MI, United States of America

Joseph M Vihtelic