Protective coating for a thermally stressed structure
Provided is a method for arranging a protective coating for a thermally stressed structure, having at least one layer of alpha-aluminium oxide or of element-modified alpha-aluminium oxide, and wherein the protective coating is applied by reactive cathodic arc vaporization. A protective coating produced by the method and a component having a protective coating is also provided.
1. A method for arranging a protective coating comprising at least one layer with aluminum oxide content on a thermally stressed structure by means of cathodic arc evaporation, wherein the thermally stressed structure comprises at least one thermal barrier coating made of a ceramic material, the method comprising:
S1) providing the thermally stressed structure in a coating chamber;
S2) providing a target as a source material for the at least one layer in the coating chamber, wherein the target comprises at least aluminium;
S3) providing a controlled oxygen partial pressure in the coating chamber; and
S4) igniting an arc so that material of the target is evaporated, which material is deposited on an outer side of the thermal barrier coating of the thermally stressed structure,
wherein the ceramic material of the thermal barrier comprises yttrium oxide-stabilized zirconium dioxide and/or gadolinium oxide-stabilized zirconium oxide, and
where the protective coating is applied as a homogeneous alpha-aluminum oxide layer, with the target additionally comprising chromium, wherein a content of chromium is measured so that the lattice constant of at least one Al—Cr—O mixed crystal which is created during the coating is adjusted within the range which lies between corundum and eskolaite.
2. The method as claimed in claim 1 , wherein the target additionally comprises elements selected from the group consisting of: titanium, hafnium, silicon, and zirconium.
3. The method as claimed in claim 1 , wherein a temperature of the substrate is at least 200° C.
4. The method as claimed in claim 1 , wherein the substrate temperature is approximately 600° C.
5. The method as claimed in claim 1 , wherein a thickness of the applied protective coating lies between 5 and 500 μm.
6. The method as claimed in claim 1 , wherein a gradient is produced in the chemical composition of the protective coating.
7. The method as claimed in claim 1 , further comprising applying the protective coating directly onto the at least one thermal barrier coating made of ceramic.
8. The method as claimed in claim 1 , wherein an adhesive layer is located between the at least one thermal barrier coating made of ceramic and the protective coating.
9. The method as claimed in claim 1 , further comprising providing a zirconium yttrium target for the adhesive layer.