Coating system for refractory metals
AssigneeHitemco, LLC
InventorCharles Clifford Berger
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Abstract
A coating system includes a diffusion coating on a refractory metal or refractory metal alloy. The coating can be applied to a component such as a rocket engine component that includes a substrate including the refractory metal and is useful to protect the substrate from high temperature oxidation. The diffusion coating process employs an activator that includes a compound of the metal to be diffused into the surface of the substrate and is a vapor phase process in which the vapor includes metal from the activator and additional from the metal source being activated. Aluminum trifluoride can be used to activate an aluminum metal source to form an aluminide coating on a refractory metal-based alloy, such as a niobium alloy.
Claims20
An engine component having a surface in direct contact with engine combustion gases during engine operation, the engine component comprising:
- a substrate formed from a substrate material comprising a refractory metal as the primary constituent;
- and
- a coating system comprising a diffusion aluminide coating formed on the substrate, the diffusion aluminide coating comprising aluminum interdiffused with the substrate material,
- the coating system defining at least a portion of the surface in direct contact with engine combustion gases during engine operation,
- wherein the diffusion aluminide coating includes at least two of the following intermetallic compounds:
- RAl, RAl2 and RAl3, where R is the refractory metal.
A method of forming a protective coating on a substrate material, the method comprising the steps of:
- providing a bed of solid particulate material comprising a combination of solid aluminum metal and a solid aluminum halide activator;
- bringing a coating chamber to a diffusion temperature with the substrate material and the bed of particulate material inside the chamber, wherein the aluminum halide activator sublimes and reacts with the aluminum metal in the bed of particulate material to form a vapor comprising aluminum from the aluminum metal in addition to aluminum from the aluminum halide activator,
- whereby aluminum from said vapor diffuses into the substrate material to form an aluminide diffusion coating,
- wherein the method is a non-contact vapor phase aluminide process in which the substrate material does not contact the solid aluminum metal or the solid aluminum halide activator in the bed of particulate material.
A rocket engine, comprising:
- a combustion chamber configured to burn fuel from a fuel source to produce combustion gases;
- a nozzle shaped to expand and accelerate the combustion gases;
- a throat through which the combustion gases pass from the combustion chamber to the nozzle,
- wherein each of the combustion chamber, nozzle, and throat is formed from a substrate material comprising 89% niobium, 10% hafnium, and 1% titanium;
- and
- a coating system disposed over a surface of at least two of:
- the combustion chamber, the nozzle, and the throat,
- wherein the coating system comprises an inwardly diffused aluminide coating having a thickness of at least 50 microns and includes the following intermetallic compounds:
- NbAl, NbAl2, and NbAl3, the coating system further comprising a ceramic-based thermal barrier coating disposed over the aluminide coating and a thermally grown oxide layer disposed between the aluminide coating and the thermal barrier coating, and
- wherein the coating system is in direct contact with the combustion gases during engine operation at said at least two of:
- the combustion chamber, the nozzle, and the throat.
Dependencies are inferred from the claim text.