Preparation of sheet by injection molding of powder, consolidation, and heat treating
A sheet is prepared by mixing a mass of metallic powders with a temporary thermoplastic binder to form an injection-moldable mixture, thereafter injection molding the injection-moldable mixture to form a sheet precursor. The sheet precursor is consolidated to a relative density of substantially 100 percent to form the sheet, and thereafter heat treated. The final sheet is preferably a nickel-base superalloy having more than about 30 volume percent of gamma prime phase, or an intermetallic such as a titanium aluminide.
1. A method for preparing a sheet of a sheet composition, comprising the steps of
providing a mass of metallic powders, wherein the mass of metallic powders together have the sheet composition;
mixing the metallic powders with a temporary thermoplastic binder to form an injection-moldable mixture; thereafter
injection molding the injection-moldable mixture onto a moving surface of a movable receiver at an injection-molding temperature above the thermoplastic temperature of the thermoplastic binder to form an injection-molded sheet precursor having a width of at least about 2 feet and a length of at least about 4 feet; thereafter
consolidating the injection-molded sheet precursor to a relative density of substantially 100 percent to form the sheet of the sheet composition, wherein the temporary thermoplastic binder is removed in the step of consolidating; and thereafter
heat treating the sheet.
2. The method of claim 1 , wherein the step of providing the mass of metallic powders includes the step of
providing the metallic powders as prealloyed metallic powders.
3. The method of claim 1 , wherein the step of providing the mass of metallic powders includes the step of
providing the net metallic composition as a nickel-base superalloy.
4. The method of claim 1 , wherein the step of providing the mass of metallic powders includes the step of
providing the net metallic composition as a nickel-base superalloy, and wherein the step of heat treating includes the step of
heat treating the net metallic composition to produce more than about 30 volume percent gamma prime phase.
5. The method of claim 1 , wherein the step of providing the mass of metallic powders includes the step of
providing the net metallic composition as a nickel-base superalloy, and wherein the step of heat treating includes the step of
heat treating the net metallic composition to produce more than about 40 volume percent gamma prime phase.
6. The method of claim 1 , wherein the step of providing the mass of metallic powders includes the step of
providing the net metallic composition as an intermetallic alloy.
7. The method of claim 1 , wherein the step of providing the mass of metallic powders includes the step of
providing the net metallic composition as a titanium-aluminide intermetallic alloy.
8. The method of claim 1 , wherein the step of providing includes the step of
providing the mass of metallic powders having a nominal sheet composition in atomic percent of from about 45 to about 49 percent aluminum and from about 48 to about 50.5 percent titanium, with the balance of other alloying and impurity elements.
9. The method of claim 1 , wherein the step of providing includes the step of
providing nonmetallic particles mixed with the metallic powders.
10. The method of claim 1 , wherein the step of mixing includes the step of
mixing the metallic powders and the temporary thermoplastic binder at a mixing temperature above the thermoplastic temperature of the thermoplastic binder.
11. The method of claim 1 , wherein the step of consolidating includes the step of
sintering the injection-molded sheet precursor.
12. The method of claim 1 , wherein the step of consolidating includes the step of
hot isostatic pressing the injection-molded sheet precursor.
13. The method of claim 1 , including an additional step, after the step of injection molding and before the step of consolidating, of
removing excess thermoplastic binder from the injection-molded sheet precursor.
14. The method of claim 1 , wherein the step of consolidating includes the step of
producing the sheet having a length dimension greater than about 100 times a thickness dimension.
15. The method of claim 1 , wherein the step of injection molding includes the steps of
providing an injection-molding apparatus including
an injection head with an injection nozzle, and
a movable receiver positioned to receive the injection-moldable mixture flowing from the injection nozzle,
loading the injection-moldable mixture into the injection head, and
forcing the injection-moldable mixture out of the injection nozzle onto the moving surface of the movable receiver, the moving surface moving away from the injection nozzle at the same linear rate as the injection-moldable mixture is forced from the injection nozzle.
16. A method for preparing a sheet of a sheet composition for use as an aircraft skin panel, comprising the steps of
providing a mass of metallic powders, wherein the mass of metallic powders together have the sheet composition that comprises a nickel-base superalloy that may be heat treated to have more than about 30 volume percent of gamma prime phase;
mixing the metallic powders with a temporary thermoplastic binder to form an injection-moldable mixture; thereafter
injection molding the injection-moldable mixture onto a moving surface of a movable receiver at an injection-molding temperature above the thermoplastic temperature of the thermoplastic binder to form an injection-molded aircraft skin panel sheet precursor; thereafter
removing excess thermoplastic binder from the injection-molded aircraft skin panel sheet precursor; thereafter
consolidating the injection-molded aircraft skin panel sheet precursor to a relative density of substantially 100 percent to form the aircraft skin panel sheet of the sheet composition, wherein the temporary thermoplastic binder is removed in the step of consolidating; and thereafter
heat treating the aircraft skin panel sheet.
17. The method of claim 16 , wherein the step of providing includes the step of
providing the mass of metallic powders comprising a nickel-base superalloy that may be heat treated to have more than about 40 volume percent of gamma prime phase.
18. The method of claim 16 , wherein the step of consolidating includes the steps of
sintering the injection-molded aircraft skin panel sheet precursor, and thereafter
hot isostatic pressing the injection-molded aircraft skin panel sheet precursor.
19. The method of claim 16 , wherein the step of consolidating includes the step of
producing the aircraft skin panel sheet having a length dimension greater than about 100 times a thickness dimension.
20. The method of claim 16 , wherein the step of injection molding includes the steps of
providing an injection-molding apparatus including
an injection head with an injection nozzle, and
a movable receiver positioned to receive the injection-moldable mixture flowing from the injection nozzle,
loading the injection-moldable mixture into the injection head, and
forcing the injection-moldable mixture out of the injection nozzle onto the moving surface of the movable receiver, the moving surface moving away from the injection nozzle at the same linear rate as the injection-moldable mixture is forced from the injection nozzle.