Method of fabricating an investment casting mold and slurry therefor

Patent metadata

Field	Value
Publication number	US-10035182-B2
Application number	US-201715804296-A
Country	US
Kind code	B2
Filing date	Nov 6, 2017
Priority date	Dec 9, 2013
Publication date	Jul 31, 2018
Grant date	Jul 31, 2018

Abstract

A method of investment casting includes casting a liquid nickel- or cobalt-based superalloy in an investment casting mold. The superalloy includes an yttrium alloying element that is subject to reactive loss during the casting. Loss of the yttrium is limited by using a zircon-containing facecoat on a refractory investment wall in the investment casting mold. The facecoat contacts the liquid nickel- or cobalt-based superalloy during the casting. Prior to the casting, a zircon-containing slurry is used to form the facecoat. After solidification of the nickel- or cobalt-based superalloy, the refractory investment wall is removed from the solidified superalloy.

First claim

What is claimed is:

1. A method of investment casting, the method comprising:
casting a liquid nickel- or cobalt-based superalloy in an investment casting mold, the liquid nickel- or cobalt-based superalloy having a composition including at least one alloying element that is subject to reactive loss during the casting, the at least one alloying element including yttrium;
limiting the loss of the yttrium element from the composition by using a zircon-containing facecoat on a refractory investment wall in the investment casting mold, the facecoat contacting the liquid nickel- or cobalt-based superalloy during the casting, wherein the facecoat includes, by weight, at least 70% of zircon; and
after solidification of the nickel- or cobalt-based superalloy, removing the refractory investment wall from the solidified superalloy.

2. The method as recited in claim 1 , wherein the refractory investment wall includes multiple refractory layers that back the facecoat.

3. The method as recited in claim 1 , wherein the refractory investment wall includes a mold shell that surrounds a mold cavity, and the mold shell includes the facecoat.

4. The method as recited in claim 1 , wherein the facecoat includes colloidal silica.

5. The method as recited in claim 1 , wherein the facecoat includes, by weight, at least 10% colloidal silica.

6. A method of investment casting, the method comprising:
casting an airfoil in an investment casting mold from a liquid nickel- or cobalt-based superalloy, the liquid nickel- or cobalt-based superalloy having a composition including at least one alloying element that is subject to reactive loss during the casting, the at least one alloying element including yttrium;
limiting the loss of the yttrium element from the composition by using a zircon-containing facecoat on a refractory investment wall in the investment casting mold, the facecoat contacting the liquid nickel- or cobalt-based superalloy during the casting, wherein the facecoat includes, by weight, at least 70% of zircon; and
after solidification of the nickel- or cobalt-based superalloy to form the airfoil, removing the refractory investment wall from the airfoil.

7. The method as recited in claim 6 , wherein the facecoat includes, by weight, at least 10% colloidal silica.

8. The method as recited in claim 7 , wherein the refractory investment wall includes multiple refractory layers that back the facecoat.

9. The method as recited in claim 8 , wherein the refractory investment wall includes a mold shell that surrounds a mold cavity, and the mold shell includes the facecoat.

10. A method of investment casting, the method comprising:
casting an airfoil in an investment casting mold from a liquid nickel- or cobalt-based superalloy, the liquid nickel- or cobalt-based superalloy having a composition including at least one alloying element that is subject to reactive loss during the casting, the at least one alloying element including yttrium;
limiting the loss of the yttrium element from the composition by using a zircon-containing layer in a multi-layer refractory investment wall of the investment casting mold, wherein the layer includes, by weight, at least 70% of zircon; and
after solidification of the nickel- or cobalt-based superalloy to form the airfoil, removing the multi-layer refractory investment wall from the airfoil.

11. The method as recited in claim 10 , wherein the layer includes, by weight, at least 10% colloidal silica.

12. The method as recited in claim 11 , wherein the refractory investment wall includes a mold shell that surrounds a mold cavity, and the mold shell includes the layer.

Assignees

• United Technologies Corp

Inventors

• Bochiechio Mario P
• Marcin John Joseph

Classifications

• B22D21/027

  Casting heavy metals with low melting point, i.e. less than 1000 degrees C, e.g. Zn 419 degrees C, Pb 327 degrees C, Sn 232 degrees C · CPC title

• B22C9/043 Primary

  Removing the consumable pattern · CPC title

• B22F2003/248

  Thermal after-treatment · CPC title

• B22C3/00

  Selection of compositions for coating the surfaces of moulds, cores, or patterns · CPC title

• B22C1/06

  for casting extremely oxidisable metals · CPC title