Slip and process for producing an aluminum diffusion layer

Abstract

The present invention relates to a slip for producing an aluminum diffusion layer which comprises an Al-containing powder and an Si-containing powder and a binder, the slurry further comprising an Al-containing powder the powder particles of which are coated with Si. The invention further relates to a process for producing an aluminum diffusion layer, comprising the following steps: providing a slurry according to any one of the preceding claims, applying the slurry to a component surface on which the aluminum diffusion layer is to be created, drying and/or curing by way of a heat treatment at a first temperature, and diffusion annealing at a second temperature.

Claims

1. A slurry for producing an aluminum diffusion layer, wherein the slurry comprises Al-containing powder, Si-containing powder, and a binder, the Al-containing powder comprising uncoated powder particles and powder particles which are coated with Si.

2. The slurry of claim 1, wherein the Al-containing powder comprises technical-grade aluminum or Al alloys and/or the Si-containing powder comprises technical-grade silicon or Si alloys.

3. The slurry of claim 1, wherein a proportion of silicon-coated aluminum powder particles as a percentage of a total number of aluminum powder particles is from 25% to 75% by weight or by volume.

4. The slurry of claim 1, wherein the binder comprises at least one substance from the group of water, alcohols, glycol compounds, phosphates, phosphate-containing substances, and thickeners.

5. The slurry of claim 1, wherein the binder comprises water, at least one glycol compound and at least one thickener.

6. The slurry of claim 1, wherein the binder comprises a thickener which comprises one or more substances from the group of pectins, guar, carob seed flour, carrageenan, cellulose ethers, polyvinyl alcohol, and silicates.

7. A slurry for producing an aluminum diffusion layer, wherein the slurry comprises Al-containing powder, Si-containing powder, and a binder comprising water, at least one glycol compound and at least one thickener, the Al-containing powder comprising powder particles which are coated with Si.

8. The slurry of claim 7, wherein a proportion of silicon-coated aluminum powder particles as a percentage of a total number of aluminum powder particles is from 25% to 75% by weight or by volume.

9. The slurry of claim 7, wherein the binder comprises a thickener which comprises one or more substances from the group of pectins, guar, carob seed flour, carrageenan, cellulose ethers, polyvinyl alcohol, and silicates.

10. A process for producing an aluminum diffusion layer, wherein the process comprises applying a slurry to a component area on which the aluminum diffusion layer is to be produced, drying and/or curing the applied slurry with a heat treatment at a first temperature, followed by a diffusion heat treatment at a second temperature, and wherein the slurry comprises Al-containing powder, Si-containing powder, and a binder, the Al-containing powder comprising powder particles which are coated with Si.

11. The process of claim 10, wherein the process further comprises blasting a surface to be treated with particles prior to application of the slurry.

12. The process of claim 11, wherein the particles are aluminum oxide particles.

13. The process of claim 10, wherein the first temperature is within a range from 100° C. to 300° C.

14. The process of claim 10, wherein the first temperature is within a range from 120° C. to 220° C.

15. The process of claim 10, wherein the second temperature is within a range from 800° C. to 1000° C.

16. The process of claim 10, wherein the second temperature is within a range from 875° C. to 925° C.

17. The process of claim 14, wherein the second temperature is within a range from 875° C. to 925° C.

18. The process of claim 10, wherein the component on which the aluminum diffusion layer is to be produced is a component of a gas turbine or an aircraft engine.

19. The process of claim 18, wherein the process involves repairing a gas turbine or an aircraft engine.

20. A process for producing an aluminum diffusion layer, wherein the process comprises applying the slurry of claim 1 to a component area on which the aluminum diffusion layer is to be produced, drying and/or curing the applied slurry with a heat treatment at a first temperature, followed by a diffusion heat treatment at a second temperature.

Description

EXAMPLE

(1) A chromium(VI)-free slip composition which can be used, in particular, for the repair of high-temperature-stressed components of aircraft engines, for example turbine blades, comprises an aluminum powder and also an aluminum powder with aluminum particles which are coated with silicon. The proportions of uncoated aluminum powder and of aluminum powder particles which are coated with silicon can, for example, be in a ratio of (0 to 1):1. The aluminum powders together with a silicon powder are taken up in a binder which consists of water, a glycol compound and a thickener.

(2) A further example of a slip comprises from 40% by weight to 50% by weight of glycol ether acetate, from 0.5% by weight to 1% by weight of thickener, from 30% by weight to 40% by weight of coated and uncoated aluminum powder and from 6% by weight to 7% by weight of silicon powder. Correspondingly, the binder can comprise from 90% by weight to 100% by weight of glycol ether acetate and from 1% by weight to 2% by weight of thickener.

(3) Such a slip is sprayed or brushed onto a surface which has been blasted with aluminum oxide particles and heated at about 150° C. to effect drying and/or curing until the binder has been dried and/or cured. If further layers of slip are applied, drying at about 80° C. after application of each layer can be useful. A diffusion heat treatment under a protective gas atmosphere, for example an argon atmosphere, at 900° C. is then carried out for some hours so as to form an aluminum diffusion layer which offers the component oxidation protection for high temperature applications on the component surface.

(4) Although the present invention has been described in detail for the example, the invention is not restricted to this example but can comprise modifications, for example the omission of individual features or the combination of different features, as long as the scope of protection of the attached claims is not left. The present disclosure comprises all combinations of all individual features presented.