Apparatus and process for refining features in an additive manufactured part
A part formed using an metal additive manufacturing process such as a turbine airfoil with an oversized feature such as an oversized hole, where the oversized hole is filled with a preform having a shape of a normal sized hole and secured within the part using a braze or weld material, and where the preform is removed to leave within the part the normal sized hole. The preform is made of a refractory material that can be removed from the part by exposure to oxygen.
1. A process for forming a hole in a part formed by a metal additive manufacturing process comprising the steps of:
forming a part with an oversized hole using a metal additive manufacturing process;
inserting a preform having a shape of a normal sized hole into the oversized hole of the part;
securing the preform in the oversized hole with a material that fills a gap between the oversized hole and the preform; and,
removing the preform so that a normal sized hole is formed in the part.
2. The process for forming a hole in a part of claim 1 , wherein:
the part is a turbine airfoil; and,
the normal sized hole is a film cooling hole.
3. The process for forming a hole in a part of claim 1 , wherein:
the preform is formed of a refractory material that can be removed by exposure to oxygen.
4. The process for forming a hole in a part of claim 1 , and further comprising the step of:
securing the preform to the oversized hole with a braze material or a weld material.
5. The process for forming a hole in a part of claim 1 , wherein:
the normal sized hole is a helical shaped hole, or a curved hole, or a slot for a seal, or a threaded hole for a fastener.
6. The process for forming a hole in a part of claim 1 , wherein:
the part is a turbine airfoil; and,
the normal sized hole is a film cooling hole with a diffusion opening.
7. The process for forming a hole in a part of claim 1 , wherein:
the metal additive manufacturing process is a direct metal laser sintering process or an electron beam melting process.
8. The process for forming a hole in a part of claim 1 , wherein:
the preform is formed substantially from Molybdenum or Tungsten or Niobium.
9. An air cooled turbine airfoil comprising an airfoil with a plurality of film cooling holes, wherein the plurality of film cooling holes are made by the process of claim 1 .
10. A part formed by a metal additive manufacturing process with a hole having surface with a low tolerance that cannot be formed from the metal additive manufacturing process by itself, the part comprising:
a wall having an oversized hole formed from a metal additive manufacturing process;
a preform having a shape of a normal sized hole;
the preform being formed from a refractory material that can be removed by exposure to oxygen;
a braze material or a weld material filling a gap between the oversized hole and the preform to secure the preform to the oversized hole; and,
wherein exposure of the preform to oxygen will remove the preform from the oversized hole and leave a normal sized hole within the wall.
11. The part formed by a metal additive manufacturing process of claim 10 , wherein the preform has been removed by exposure to oxygen.
12. The part formed by a metal additive manufacturing process of claim 10 , wherein:
after exposure of the preform to oxygen such that the preform is removed,
the part is an air cooled turbine airfoil; and,
the hole is a film cooling hole.
13. The part formed by a metal additive manufacturing process of claim 10 , wherein:
the normal sized hole is a helical shaped hole, or a curved hole, or a slot for a seal, or a threaded hole for a fastener.
14. The part formed by a metal additive manufacturing process of claim 10 , wherein:
the preform is formed substantially from Molybdenum or Tungsten or Niobium.
15. The part formed by a metal additive manufacturing process of claim 12 , wherein: the film cooling hole has a diffusion opening.
16. A process of forming an air cooled turbine airfoil from a metal additive manufacturing process comprising the steps of:
forming an air cooled turbine airfoil with a plurality of film cooling holes from an additive manufacturing process in which the film cooling holes are formed oversized;
inserting a preform having a shape of a non-oversized film cooling hole into each of the oversized film cooling holes;
securing the preforms to the oversized film cooling holes with a material having a melting temperature of at least as high as the material of which the air cooled turbine airfoil is made from; and,
removing the preforms to leave non-oversized film cooling holes in the air cooled turbine airfoil.
17. The process of forming an air cooled turbine airfoil from a metal additive manufacturing process of claim 16 , and further comprising the step of:
securing the preform to the oversized hole with a braze material or a weld material.
18. The process of forming an air cooled turbine airfoil from a metal additive manufacturing process of claim 16 , wherein:
the preform is formed of a refractory material that can be removed by exposure to oxygen.