EP1573090A2 - Method for the deposition of an alloy on a substrate - Google Patents

Abstract

In previously known electrodeposition methods, alloys can be deposited only badly on a substrate from the components thereof. The inventive method allows an alloy layer to be deposited on a substrate (13) by pulsing the current/voltage used for electrode position.

Description

 Process for depositing an alloy on a substrate

The invention relates to a method for depositing an alloy on a substrate.

Various methods are known for applying layers on a substrate. These are e.g. Experience plasma spraying, galvanic deposition or vapor deposition, etc.

An article by G. Devaray in Bulletin of Electrochemistry 8 (8), 1992, pp. 390-392 with the title "Electro deposited composites - a review on new technologies for aerospace and other field" gives an overview of processes for the electrochemical deposition of layers.

DE 101 13 767 AI discloses an electrolytic plating process.

DE 39 43 669 C2 discloses a method and a device for electrolytic surface treatment, in which the mass parts used for coating are mixed by oscillating movement and / or rotating movement, so that a uniform electrolytic layer is deposited.

Further electrolytic processes for coating are known from GB 2 167 446 A, EP 443 877 AI and from the article by J. Zahavi et al in Plating and Surface Finishing, Jan. 1982, p. 76 ff. “Properties of electrodeposited composite coatings "in which undissolved particles are used in the electrolyte in order to separate them in the layer.

In Electrochemical Society Proceedings Vol. 95-18, pp. 543 ff. By Sarhadi et al. with the title “Development of a low current density electroplating bath ... "describes the use of baths containing cobalt, nickel or iron compounds.

The US-PS 6,375,823 Bl describes an electrolytic

Coating method using an ultrasonic probe.

DE 195 45 231 AI describes a method for the electrolytic deposition of metal layers, in which a pulse current or pulse voltage method is used. However, this is only used to reduce the signs of aging in the deposition baths.

The US 2001/00 54 559 AI discloses an electrolytic

Coating process using pulsed currents to prevent the undesirable evolution of hydrogen during electrolytic coating of metals.

DE 196 53 681 C2 discloses a method for electrolytic deposition from a pure copper layer, in which a pulse current or pulse voltage method is used.

DE 100 61 186 Cl describes a method for galvanic deposition in which periodic current pulses are used.

In the article "Electrodeposited composite coatings for protection from high te perature corrosion" in Trans IMF 1987, 65, 21ff, V. Sova describes an electrolytic deposition process in which undissolved particles in the electrolyte are used for the layer to be applied. The use of pulse currents is also the case described. Layers applied with the known methods have poor adhesion to the substrate under the conditions of some applications. In addition, only materials with a constant composition can be deposited.

It is therefore an object of the invention to overcome the problems mentioned above.

The object is achieved by a method for depositing an alloy on a substrate according to claim 1.

The use of pulsed currents or the generation of graded layers improves the adhesion of layers to the substrate or the deposition rate.

Further advantageous refinements of the method are listed in the claims.

An embodiment of the invention is explained in more detail in the figures.

Show it:

Figure 1 shows an apparatus for performing the method according to the invention, and

Figure 2 shows a sequence of a current / voltage pulse, which is used for a method according to the invention.

FIG. 1 shows a device 1 for carrying out the method according to the invention.

An electrolyte 7, an electrode 10 and a substrate 13 to be coated are arranged in a container 4. The substrate 13 to be coated is, for example, a combustion chamber lining, a housing part or a

Turbine blade made of a nickel, cobalt or iron based super alloy of a gas or steam turbine, the but can also have a layer on the substrate (MCrAlY).

The substrate 13 and the electrode 10 are electrically conductively connected to a current / voltage source 16 via electrical leads 19. The current / voltage source 16 generates pulsed electrical currents / voltages (FIG. 2).

The individual constituents of an alloy which are to be deposited on the substrate 13 are contained in the electrolyte 7. For example, the electrolyte 7 contains a first one

Component 28 and a second component 31 one

Alloy.

The components 28, 31 are deposited on the substrate 13 by a suitable choice of the process parameters (FIG. 2).

Likewise, gradients in the chemical composition can be generated in the layer to be produced by suitable selection of the process parameters. For example, an alloy MCrAlY is deposited on the substrate 13, where M stands for at least one element from the group iron, cobalt or nickel. The alloy elements Cr, Al, Y and optionally further elements are introduced either by adding suitable soluble salts to the electrolyte or by suspending fine-grained, insoluble powders in the electroplating bath, which are solid

Separate particles. For example. At least two components are dissolved in the electrolyte 7, for example in the form of salts. The layer can be homogenized or compressed by a subsequent thermal process or certain phases can be set in the layer.

An ultrasound probe 22, which can be arranged in the electrolyte 7 and is controlled by an ultrasound transmitter 25, improves the hydrodynamics and the mixing of the components 28, 31 in the region of the substrate 13 and accelerates the deposition process. The oscillation frequency is, for example, above 1 kHz. The current / voltage level, the pulse duration and the pulse pause are defined for at least one, in particular for each component 28, 31 of the alloy.

FIG. 2 shows an exemplary sequence of

Current pulses (40) that are repeated.

A sequence 34 consists of at least two blocks 37. In FIG. 2 there are four blocks 37. However, three, five or more blocks 37 can also be used.

Each block 37 consists of at least one current pulse 40. In FIG. 2 there are three, four or six current pulses 40. However, two, five or more than six current pulses 40 can also be used per block 37.

A current pulse 40 is characterized by its duration t _on , the height I _mx and its shape (rectangle, triangle, ...). The pauses between the individual current pulses 40 (t _off ) and the pauses between the blocks 37 are equally important as process parameters.

The sequences can also change over time.

The sequence 34 consists, for example, of a first block 37 with three current pulses 40, between which there is again a pause. This is followed by a second block 37, which has a greater or lesser current level since it is matched to another component 28, 31, and consists of six current pulses 40. After a further pause, four current pulses 40 follow in the opposite direction, i.e. with changed polarity to achieve a correction of the alloy composition, the hydrogen desorption or an activation.

Each block 37 can thus have a different number of current pulses 40, pulse durations t _on or pulse _pauses t _Qff . At the end of sequence 34 there follows another block 37 with four current pulses.

The sequence can be repeated several times.

The individual pulse times t _on are preferably on the order of approximately 1 to 100 milliseconds. The time duration of block 37 is of the order of up to 10 seconds, so that up to 5000 pulses are transmitted in a block 37.

It is optionally possible to assign a low potential (base current) both during the pulse sequences and during the pause time. An interruption of the electrodeposition, which can cause inhomogeneities, is thus avoided.

A block 37 is matched with its parameters to a component 28, 31 of the alloy in order to achieve the best deposition of this component 28, 31. These can be determined in individual experiments. An optimized block 37 leads to an optimized deposition of the component optimized to this block 37, i.e. the duration and the type of deposition is improved. The other components are also still separated. This optimization can be carried out for at least one further, for example all, constituent parts 31 of the alloy. The optimized composition of the components 28, 31 is thus achieved.

For example, by the duration of the individual blocks 37, the proportion of the components 28, 31 in the to be applied

Layer.

Gradients can also be created in the layer.

This happens because the duration of the block 37, the current / voltage level or the number of pulses 40 per block, which is optimally matched to a component 28, 31, is extended or shortened accordingly (ie sequence 34 is changed).

A sequence 34 can also be changed if e.g. the deposition rate of a component 28, 31 changes over time due to the layer already deposited.

Other non-alloy components, e.g. Secondary phases in which electrolytes 7 are contained and deposited.

Claims

claims 1. Method for the electrolytic deposition of an alloy with at least two components as a layer on a substrate (13) which is arranged in an electrolyte (37) in which (37) at least two components (28, 31) Alloy are suspended and / or dissolved, wherein several current / voltage pulses (40) are repeatedly used for the electrolytic deposition, which are combined in a sequence (34), the sequence (34) consisting of at least two different blocks (37), wherein a block (37) consists of at least one current pulse (40), and wherein a block (37) each has a component (28, 31) of the alloy is matched in order to achieve the best deposition of the component (28, 31). 2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the electrolyte (7) is set in mechanical vibrations. 3. The method of claim 2, d a d u r c h g e k e n n z e i c h n e t that an ultrasonic probe (22) is operated in the electrolyte (7). , The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that one used for electrodeposition Current / voltage pulse (40) is determined by its time profile, which in particular has a rectangular or triangular shape. 5. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that a current / voltage pulse (40) is used for electrolytic deposition, both positive and negative current / voltage pulses (40) being used. 6. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that a block (37) is determined by a number of current pulses (40), pulse duration (t _on ), pulse _pause (t _0ff ), current level (I _max ) and temporal course. 7. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that each block (37) is matched to one component (28, 31) of the alloy in order to achieve the best composition of the components (28, 31). A method according to claim 1, characterized in that as an alloy, a MCrAlY layer is deposited on a substrate (13), where M is at least one element from the group iron, cobalt or nickel. 9. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that gradients in the material composition are produced in an alloy layer to be produced. 10. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that a base current is superimposed on the current pulses (40) and / or the pauses.