Leading-edge structures for airfoils and systems and methods for fabricating the same
A system and method for fabricating a protective leading-edge structure for an airfoil includes system includes a mandrel and a cold spray additive manufacturing apparatus. The cold spray additive manufacturing apparatus is configured to deposit a metallic powder on a tool surface of the mandrel to form an inner layer, intermediate layers, and an outer layer of the leading-edge structure. The inner layer forms an inner surface of the leading-edge structure. The outer layer forms an outer surface of the leading-edge structure. The intermediate layers form a thickness of the leading-edge structure. The inner surface of the leading-edge structure is configured to be coupled to the airfoil such that the outer surface of the leading-edge structure forms a portion of a leading edge and a portion of an aerodynamic surface of the airfoil.
1. A system for fabricating a leading-edge structure of an airfoil, the system comprising:
a mandrel comprising a tool surface; and
a cold spray additive manufacturing apparatus comprising a computer and programming that is configured to:
deposit a metallic powder at a first velocity and at a first density on the tool surface of the mandrel to form an inner layer of the leading-edge structure;
deposit the metallic powder at a second velocity, which is greater than the first velocity, and at a second density, which is greater than the first density, on the inner layer to form a number of intermediate layers of the leading-edge structure; and
deposit the metallic powder at the second velocity and at a third density, which is greater than the second density, on one of the intermediate layers to form an outer layer of the leading-edge structure,
wherein:
the first velocity is below a level of permanent adhesion of the metallic powder to the tool surface of the mandrel;
the second velocity is above a level of permanent adhesion of the metallic powder to the inner layer and any one of the intermediate layers;
the inner layer forms an inner surface of the leading-edge structure;
the outer layer forms an outer surface of the leading-edge structure that is opposite the inner surface;
the intermediate layers form a thickness of the leading-edge structure between the inner surface and the outer surface; and
the inner surface of the leading-edge structure is configured to be coupled to the airfoil such that the outer surface of the leading-edge structure forms a portion of a leading edge and a portion of an aerodynamic surface of the airfoil.
2. The system of claim 1 , wherein the metallic powder comprises Niobium powder.
3. The system of claim 1 , wherein the metallic powder comprises a refractory metal powder.
4. The system of claim 1 , wherein the first velocity is between approximately 5 percent and approximately 25 percent less than the second velocity.
5. The system of claim 1 , wherein:
the mandrel is a monolithic structure; and
the tool surface is a continuous surface.
6. The system of claim 1 , wherein:
the mandrel comprises a first hardness;
the metallic powder comprises a second hardness; and
the first hardness is greater than the second hardness.
7. The system of claim 1 , wherein:
the mandrel has a longitudinal axis; and
the mandrel is configured for rotating about the longitudinal axis relative to the cold spray additive manufacturing apparatus during deposition of the metallic powder.
8. The system of claim 1 , wherein the mandrel is rotatable about a longitudinal axis relative to the cold spray additive manufacturing apparatus.
9. A method for fabricating a leading-edge structure of an airfoil, the method comprising:
cold spraying a metallic powder at a first velocity and at a first density on a tool surface of a mandrel to form an inner layer of the leading-edge structure;
cold spraying the metallic powder at a second velocity, which is greater than the first velocity, and at a second density on the inner layer to form a number of intermediate layers of the leading-edge structure; and
cold spraying the metallic powder at the second velocity and at a third density, which is greater than the second density, on one of the intermediate layers to form an outer layer of the leading-edge structure,
wherein:
the first velocity is below a level of permanent adhesion of the metallic powder to the tool surface of the mandrel:
the second velocity is above a level of permanent adhesion of the metallic powder to the inner layer and any one of the intermediate layers:
the inner layer forms an inner surface of the leading-edge structure;
the outer layer forms an outer surface of the leading-edge structure that is opposite the inner surface;
the intermediate layers form a thickness of the leading-edge structure between the inner surface and the outer surface; and
the inner surface of the leading-edge structure is configured to be coupled to the airfoil such that the outer surface of the leading-edge structure forms a portion of a leading edge and a portion of an aerodynamic surface of the airfoil.
10. The method of claim 9 , wherein the metallic powder comprises Niobium powder.
11. The method of claim 9 , wherein the metallic powder consists essentially of Niobium powder.
12. The method of claim 9 , wherein the metallic powder consists of Niobium powder.
13. The method of claim 9 , wherein the metallic powder comprises a refractory metal powder.
14. The method of claim 9 , wherein the first velocity is between approximately 5 percent and approximately 25 percent less than the second velocity.
15. The method of claim 9 , further comprising releasing the inner surface of the leading-edge structure from the tool surface of the mandrel,
wherein:
the mandrel is a monolithic structure;
the tool surface is a continuous surface;
the mandrel comprises a first hardness;
the metallic powder comprises a second hardness; and
the first hardness is greater than the second hardness.
16. The method of claim 9 , further comprising rotating the mandrel about a longitudinal axis during cold spraying of the metallic powder.
17. The method of claim 9 , further comprising releasing the inner surface of the leading-edge structure from the tool surface of the mandrel,
wherein:
the mandrel comprises a first hardness;
the metallic powder comprises a second hardness; and
the first hardness is greater than the second hardness.
18. A leading-edge structure of an airfoil comprising:
an inner surface that is configured to be coupled to the airfoil; and
an outer surface that is opposite the inner surface and that is configured to form a portion of a leading edge and a portion of an aerodynamic surface of the airfoil,
wherein:
the leading-edge structure is fabricated using a cold spray additive manufacturing process by:
cold spray depositing Niobium powder at a first velocity and at a first density to form an inner layer on a tool surface of a mandrel;
cold spray depositing the Niobium powder at a second velocity, which is greater than the first velocity, and at a second density, which is greater than the first density, to one or more intermediate layers on the inner layer; and
cold spray depositing the Niobium powder at the second velocity and at a third density, which is greater than the second density, to form an outer layer on the intermediate layers;
the first velocity is below a level of permanent adhesion of the Niobium powder to the tool surface of the mandrel; and
the second velocity is above a level of permanent adhesion of the Niobium powder to the inner layer and any one of the intermediate layers.
19. The leading-edge structure of claim 18 , further comprising one of a dihedral shape, an anhedral shape, and a non-linear twist about a spanwise direction.
20. The leading-edge structure of claim 18 , wherein the first velocity is between approximately 5 percent and approximately 25 percent less than the second velocity.