System and process to provide self-supporting additive manufactured ceramic core

Abstract

A core for use in casting an internal cooling circuit within a gas turbine engine component, the core including a core body with an outer skin in which a core body additively manufacturing binder is locally eliminated. A method of manufacturing a core for casting a component, including casting a core body for at least partially forming an internal passage architecture of a component; and forming an outer skin on the core body in which a core body binder is locally eliminated.

Claims

1. A method of manufacturing a precursor for casting a component, comprising: additively manufacturing a precursor body for at least partially forming an internal passage architecture of a component; and forming an outer skin on the additively manufactured precursor body in which an additively manufacturing binder is locally eliminated, the outer skin forming only a visible region of the outer surface of the precursor body such that the outer skin is sintered to retain the shape of the precursor body during a firing process that de-binds and sinters non-outer skin regions of the precursor body; and firing the precursor body to de-bind and sinter the non-outer skin regions of the precursor body subsequent to forming the outer skin.

2. The method as recited in claim 1, further comprising using a directional energy source to form the outer skin.

3. The method as recited in claim 1, further comprising using a laser to form the outer skin.

4. The method as recited in claim 3, wherein the laser is a 100 W laser source that is operated for 0.050 seconds.

5. The method as recited in claim 1, further comprising forming the outer skin only along a line of sight from a directional energy source of the outer surface of the precursor body.

6. The method as recited in claim 5, wherein the visible region is along the line of sight from a directional energy source directed at an outer surface of the precursor body.

7. The method as recited in claim 1, wherein the non-outer skin regions of the precursor body are visually shielded regions of the precursor body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:

(2) FIG. 1 is a general schematic view of an exemplary actively cooled component as a representative workpiece with an additively manufactured core;

(3) FIG. 2 is a general schematic view of an additively manufactured core;

(4) FIG. 3 is an expanded cross section of the additively manufactured core along the line 3-3 of FIG. 2 illustrating the outer skin;

(5) FIG. 4 is a flow diagram of a method of manufacturing a core for casting a component according to a non-liming embodiment;

(6) FIG. 5 is an expanded cross section of the core in which a laser is utilized to form an outer skin to allow the core to be self-supportive during the firing process; and

(7) FIG. 6 is a graphical representation of the laser depth effect on the core.

DETAILED DESCRIPTION

(8) FIG. 1 schematically illustrates a general perspective view of an exemplary component 20, e.g., an actively cooled airfoil segment of a gas turbine engine. It should be appreciated that although a particular component type is illustrated in the disclosed non-limiting embodiment, other components, such as blades, vanes, exhaust duct liners, nozzle flaps, and nozzle seals, as well as other actively cooled components will also benefit herefrom. These components, for example, operate in challenging high-temperature environments such as a hot section of a gas turbine engine and have aggressive requirements in terms of durability and temperature allowances.

(9) The component 20 includes internal passage architecture 30 formed by a core 200 (FIG. 2). FIG. 3 is an expanded cross-sectional view of the core 32 along the line 3-3 of FIG. 2. The internal passage architecture 30 may include various passages, apertures and features. In this example, the component 20 may be a rotor blade that generally includes a root section 40, a platform section 50 and an airfoil section 60. The airfoil section 60 is defined by an outer airfoil wall surface 68 between a leading edge 70 and a trailing edge 72. The outer airfoil wall surface 68 defines a generally concave shaped portion forming a pressure side 68P and a generally convex shaped portion forming a suction side 68S typically shaped for use in a respective stage of a high pressure turbine section (FIG. 3).

(10) The outer airfoil wall surface 68 extends spanwise from the platform section 50 to a tip 74 of the airfoil section 60. The trailing edge 72 is spaced chordwise from the leading edge 70. The airfoil has a multiple of cavities or passages for cooling air as represented by the supply passages 80, 82, 84 which may extend through the root section 40. The passages extend into the interior of the airfoil section 60 and may extend in a serpentine or other non-linear fashion. It should be appreciated that the passage arrangement is merely illustrative and that various passages may alternatively or additionally be provided.

(11) With reference to FIG. 4, one disclosed non-limiting embodiment of a method 300 to manufacture the core 200 initially includes additively manufacturing the core 200 (Step 302). It should be appreciated that although a particular remanufacture method is depicted, other manufacture, repair, and/or remanufacture processes and methods will also benefit herefrom. The core 200 may be additively manufactured from a ceramic such as silica or alumina and a consumable part off the casting process. In traditional casting processes, the core is created by injection molding of powdered ceramic and binder into a mold. Newer processes have been developed where the ceramic is suspended in a liquid binder than can be solidified using a laser or UV light. This process (called ceramic stereo lithographyCSL) typically utilizes an off-the-shelf lithographic fluid with a traditional ceramic suspended in the solution.

(12) Next, the core 200 may optionally be cleaned or otherwise machined (Step 304). That is, the core 200 may be processed subsequent to the additive manufacturing.

(13) Next, an outer skin 400 of the core 200 is consolidated (Step 306) via, for example, a laser (FIG. 3) prior to full core de-bind and sintering (step 308) in a furnace. Relatively low power lasers, e.g., about 100 W, could be utilized to directly sinter silica. In one example, the silica in the outer skin 400 may be sintered at about 2192 F. The outer skin 400 of the core 200 in this embodiment is about 1-2 mils (thousands of an inch).

(14) In one example, the transient thermal results of the core 200 under laser heating using a 100 W laser source for 0.050 seconds (FIG. 5). As is visible in the results, the local heating penetrates a shallow depth into the part leaving the larger portion deeper into the core un-affected (FIG. 6). This local heating reduces thermal strains in the part and reduces the risk of core cracking that a deeper heat penetration would produce.

(15) In this embodiment the laser is directed at the core 200 such that only the visibly exposed surfaces are impacted by the laser. That is, the laser only affects the portion of the core 200 that is within line-of-sight of the laser. That is, the outer skin 400 in which the sintering need not fully encapsulate the component, i.e., the laser does not raster the entire surface, for the process to provide structural rigidity during firing.

(16) The pre-sintered portions of the outer skin 400 provide retaining strength to the core 200 during the full furnace burn out process which thereby eliminates the need for setters and reduced development time for processing of a new additive core design. The process facilitates an increase in core yield by strengthening cores prior to firing by pre-sintering the surface and thereby decreases cost for processing of additive cores.

(17) The use of the terms a, an, the, and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier about used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as forward, aft, upper, lower, above, below, and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

(18) Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

(19) It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

(20) Although particular step sequences are shown, described, and claimed, it should be appreciated that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

(21) The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be appreciated that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.