Alluminide coatings containing silicon and yttrium for superalloys and method of forming such coatings
Aluminide coatings or layers ( 14 ) for jet engine components ( 10 ) and a process for forming aluminide layers ( 14 ) that include additions of silicon and yttrium. A superalloy substrate ( 12 ) of the component ( 10 ) is initially coated with a layer of a silicon-containing material. The substrate ( 12 ) is then aluminided, for example by a chemical vapor deposition process, and is exposed to a yttrium-containing material during the aluminiding process to form the aluminide layer ( 14 ) containing silicon and yttrium. A ceramic thermal barrier layer ( 24 ) of yttria-stabilized zirconia may be optionally applied over the aluminide layer ( 14 ). Another optional zirconia layer ( 26 ) maybe provided between the aluminide layer ( 14 ) and the ceramic thermal barrier layer ( 24 ). The present invention provides a silicon- and yttrium-containing aluminide layer ( 14 ) having improved durability, either as a standalone environmental coating or as a bond coat for a subsequently-applied ceramic thermal barrier layer ( 24 ).
1 . A jet engine component having a working surface exposed to the environment when in service, the jet engine component consisting essentially of:
a substrate of a nickel-based superalloy material; and
an aluminide layer including silicon and yttrium, the aluminide layer defining the working surface of the jet engine component.
2 . The jet engine component of claim 1 wherein yttrium is distributed with a uniform concentration through the aluminide layer.
3 . The jet engine component of claim 1 wherein yttrium has a concentration gradient in the aluminide layer.
4 . The jet engine component of claim 3 wherein a concentration of yttrium in the aluminide layer is greatest at the working surface.
5 . The jet engine component of claim 1 wherein a concentration of yttrium in the aluminide layer is less than about 0.5 wt %.
6 . A jet engine component comprising:
a substrate comprising a nickel-based superalloy;
an aluminide layer including silicon and yttrium and disposed on the substrate; and
a zirconia layer disposed on the aluminide layer.
7 . The jet engine component of claim 6 further comprising:
a ceramic thermal barrier layer disposed on the zirconia layer.
8 . The jet engine component of claim 7 wherein said ceramic thermal barrier layer comprises yttria-stabilized zirconia.
9 . The jet engine component of claim 6 wherein said zirconia layer has a surface roughness effective to increase the surface area for the interface with the ceramic thermal barrier layer for promoting adhesion.
10 . The jet engine component of claim 6 wherein the yttrium is distributed with a uniform concentration through the aluminide layer.
11 . The jet engine component of claim 6 wherein the yttrium is distributed with a concentration gradient in the aluminide layer.
12 . The jet engine component of claim 11 wherein a concentration of yttrium in the aluminide layer is greatest at an interface between the aluminide layer and the zirconia layer.
13 . The jet engine component of claim 6 wherein a concentration of yttrium in the aluminide layer is less than about 0.5 wt %.
14 . A deposition process comprising:
applying a silicon-containing material to at least a portion of a surface of a jet engine component of a nickel-based superalloy;
exposing the jet engine component with the silicon-containing material to a donor material including a metal to begin forming an aluminide layer including metal from the donor material; and
exposing the thickening aluminide layer to a yttrium-containing material.
15 . The method of claim 14 wherein at least the surface portion with the silicon-containing material is not exposed to the yttrium-containing material during an initial portion of the exposure time.
16 . The method of claim 14 further comprising:
after the intermetallic layer is formed, forming a zirconia layer on at least the surface portion with the silicon-containing material.
17 . The method of claim 16 further comprising:
forming a ceramic thermal barrier layer on the zirconia layer.
18 . The method of claim 16 wherein forming the zirconia layer further comprises:
depositing a zirconium layer on the surface portion; and
converting the zirconium layer to zirconia.
19 . The method of claim 18 wherein the zirconium layer is deposited while the metal component is in the deposition environment.
20 . The method of claim 18 wherein the zirconium layer is deposited at a deposition rate effective to provide surface texturing.
21 . The method of claim 20 further comprising:
forming a ceramic thermal barrier layer on the textured surface of the zirconia layer, the surface texturing enhancing the adhesion of the ceramic thermal barrier layer to the jet engine component.
22 . The method of claim 14 further comprising:
forming a ceramic thermal barrier layer on the aluminide layer.
23 . The method of claim 14 further comprising:
heating the jet engine component at a temperature sufficient to diffuse yttrium from the yttrium-containing material into the aluminide layer.