EP1213372A2 - Process and arrangement for the galvanic deposition of nickel, cobalt, nickel alloys or cobalt alloys with periodic current pulses and use of the process - Google Patents

Abstract

A method for galvanically depositing nickel, cobalt, nickel alloys or cobalt alloys in a galvanic bath includes using electrolytes containing nickel compounds or cobalt compounds. At least one anode and at least one cathode of the bath are subject to periodic current pulses. The IA/IC ratio of the anode current density IA to the cathode current density IC is selected to be greater than 1 and smaller than 1.5, where the anode current density IA and the cathode current density IC are defined as current densities with respect to a deposition body on which deposition occurs during the application of periodic current pulses where the deposition body serves as anode and cathode respectively. The charge ratio QA/QC=TAIA/TCIC of the charge QA, transported during anode pulse of duration TA, to the charge QC transported during a cathode pulse of duration TC, is between 30% and 45%. A bath for carrying out the method may have contoured anodes, current restrictors, a cleaning device for the electrolyte, and a circulating device with recycling of the electrolyte through nozzles.

Description

The present invention relates to a method for galvanic deposition of nickel, cobalt, nickel alloys or cobalt alloys in one galvanic bath using a nickel compound or cobalt compound such as electrolytes containing sulfates or sulfamates or chlorides. Such electrolytes for electrodeposition are, for example known from DE 25 58 423, DE 22 18 967, US 2,470,775 and EP 0 835 335. At least one anode and at least one cathode are used for the deposition periodic current pulses are applied to the bath. Such procedures using current pulses are, for example, from the prior art the already mentioned publications US 2,470,775 and EP 0 835 335.

In principle, such processes can be used to deposit nickel, cobalt, Nickel alloys or cobalt alloys in a galvanic bath respectively. A particular problem arises, however, when the components that certain mechanical should be produced by such a deposition Properties such as a specified strength or a specified Should have ductility. Such a problem arises especially when the component to be manufactured later with other components to be permanently connected, for example welded should. As a rule, there are certain minimum requirements for stretchability given so that a welded connection between a galvanically generated Nickel or cobalt layer or a layer of a nickel or Cobalt alloy and other components with sufficient strength and durable Durability of the welded joint can be realized. However, will Excessive ductility of the corresponding parts to be welded Achieved layer, so the strength of the corresponding layer decreases, so that the corresponding layer may no longer meet the specified Mechanical strength requirements are sufficient. This is especially true for components that are to be exposed to relatively high loads, as can occur, for example, in components in rocket engines. The thrust chambers of rocket engines should be mentioned specifically for this purpose, which essentially consist of the components injection head, combustion chamber and Thrust nozzle exist.

It has been found that those known from the prior art Process does not have the necessary properties of the electrodeposited Nickel or cobalt layers or layers of the nickel or cobalt alloy can guarantee that an inseparable connection of such Layer with other components, such as those made of an alloy Base of iron or nickel, especially for welding, indispensable Are a requirement.

The object of the present invention is therefore a method for galvanic Deposition of nickel, cobalt, nickel alloys or cobalt alloys to be provided in a galvanic bath in which at least one Anode and at least one cathode of the bath with periodic current pulses is applied and with the nickel or cobalt layers or layers a nickel or cobalt alloy can be created that are inseparable from other components can be connected, especially with others Components can be welded.

This object is achieved by the features of claims 1 and 16.

In the method according to the invention for the electrodeposition of nickel, cobalt, nickel alloys or cobalt alloys in a galvanic bath, an electrolyte is used which contains the corresponding nickel compounds or cobalt compounds, in particular sulfates or sulfamates or chlorides. For the deposition, periodic current pulses are applied to at least one anode and at least one cathode of the bath, ie a so-called pulse plating process is used. A deposition body on which a layer of the corresponding material is to be deposited normally acts as the cathode. According to the invention, the ratio I _A / I _C from the anode current density I _A to the cathode current density I _{C is selected to be} greater than 1 and less than 1.5 and the charge ratio Q _A / Q _C = (T _A · I _A ) / ( T _C · I _C) of the transported during an anode pulse of the duration T _a charge Q _a is to be transported during a cathode pulse of the duration T _C charge Q _C between 30 and 45.

It has been found that only with such a choice of conditions can the properties necessary for an inseparable connection of the deposited layer to other components be achieved, particularly with regard to the strength and extensibility of the layer. In the prior art according to EP 0 835 335, on the other hand, it is proposed in particular to choose a ratio I _A / I _C that is at least 1.5. Suitable parameter ranges for achieving a layer with the aforementioned properties are not dealt with in this document. Nothing is said there either about a suitable choice of the ratio Q _A / Q _C.

In particular, it can be provided that the ratio I _A / I _{C is} between 1.2 and 1.45, in particular between 1.3 and 1.4, and the charge ratio Q _A / Q _C = (T _A · I _A ) / (T _C · I _C ) is between 35 and 40. Particularly advantageous properties of the deposited layer, in particular with regard to the strength and the extensibility, can be determined for these parameter ranges.

For an improved and more uniform deposition of the layer on a To achieve deposition bodies, which ultimately also the resilience of Layer over its entire extent can be provided that at least one contoured anode is used for the deposition whose contour is adapted to the contour of the deposition body to deposit the nickel, cobalt, nickel alloy or cobalt alloy is. This adaptation of the anode contour can in particular an almost constant distance over the entire contour of the deposition body be achieved between the anode and the deposition body, which is a enables more uniform deposition.

In the event that several anodes are provided in the bath, at least for one of the anodes closest to the deposition body are used, a contoured anode. For the deposition body the effect of contouring affects the closest anode the anode is stronger than for anodes further away, i.e. that for these more distant anodes can each be used without contouring that are less expensive and independent of the special shape of the deposition body can be used. So can through this suitable combination of contoured and non-contoured Anodes an optimum in terms of the quality of the deposition as well as the necessary effort can be achieved.

A contoured container, for example, can be used to form the contoured anode be used for the ions of the nickel to be deposited or Cobalt or the nickel alloy or cobalt alloy is permeable and the with bodies made of nickel, cobalt or a nickel alloy or cobalt alloy is filled. Special containers for such bodies are basically made DE 25 58 423 in the form of titanium or plastic baskets known there with Nickel pellets are filled, but there is no contouring of the container is provided.

As an alternative to such containers, it can also be used as a contoured one Anode a solid electrode body can be used, the at least one Coating of the nickel, cobalt or the deposit to be deposited Has nickel alloy or cobalt alloy or even made of solid Nickel, cobalt or a massive nickel alloy or cobalt alloy.

It may be necessary during the separation process that a targeted Influencing the deposition is necessary for different areas of the Separator body should be different. This influence can in addition or alternatively to the aforementioned measure of the contoured Anodes are made. For this it can be provided that the deposition body at least for part of the total deposition time is partially shielded by current shutters. In the shielded areas then during the time these areas are shielded, reduced deposition compared to the unshielded Areas. This can have a local influence on layer properties such as in particular the layer thickness, but possibly also the mechanical layer properties realized on the deposition body become.

In particular, the flow orifices in those areas of the deposition body be arranged in which a preferred deposition he follows. This can result in excessive layer growth in these areas compared to other areas can be prevented and thus a more homogeneous Layer growth realized over the entire deposition body become.

It can preferably be a removal of disruptive foreign elements or other suspended particles from the bath are provided, to get the purest possible electrolyte solution. This can at least Before starting the deposition, cleaning the electrolyte using activated carbon and / or hydrogen peroxide. In particular, can be used for cleaning of the electrolyte before the start of the deposition 0.5 g / l to 5 g / l, in particular 1g / l to 3g / l activated carbon can be used and 0.5 ml / l to 3 ml / l, in particular 1ml / l to 2ml / l 30% hydrogen peroxide can be used.

However, in order to achieve such a cleaning not only at the beginning of the process to guarantee the purest possible electrolyte solution, but this purity One can also maintain the process as far as possible Cleaning of the electrolyte alternatively or additionally during the deposition respectively. In a preferred development of the invention, this is filtering of the electrolyte, for example, during the deposition activated carbon filter, on the other hand, foreign elements removed from the electrolyte by a selective bath. Such a selective bath corresponds to a galvanic bath, in which by a targeted control the flows a targeted separation of foreign elements and thus their removal from the electrolyte. The one cleaned in this way Electrolyte then ideally contains only the desired elements, in In the case of a nickel electrolyte then ideally only nickel or nickel alloys in the compounds mentioned at the beginning, in the case of a cobalt electrolyte ideally only cobalt or cobalt alloys in the beginning mentioned connections. The cleaned electrolyte is then the galvanic Bad fed again.

The electrolyte can also be circulated, wherein the electrolyte is circulated by at least one circulation pump and the electrolyte is returned to the bath by means of nozzles. The In particular, nozzles can now be designed and arranged in the bath that the circulation of the bath is promoted by the nozzles and / or a flow of the electrolyte directed onto the deposition body is achieved. In this case, the nozzles do not only serve the purpose of Circulation and return of the electrolyte to the bath, but through this optimized type of return, the separation process in the bathroom is favored, because there is always an optimal mixing or targeted feeding of a as pure as possible electrolyte to the deposition body is guaranteed.

The method according to the invention is basically for the production of the most varied Suitable components that are later unsolvable with other components connected, for example to be welded. The procedure is however Particularly suitable for the production of components that are subject to high loads are exposed. This applies, for example, to components for rocket engines, here in particular the application of the method for production of injection heads and / or combustion chambers and / or thrusters for Rocket engines should be mentioned. It can also be used for others Components are used that are subject to high loads in later operation, and therefore must have sufficient strength, but still should have sufficient elasticity, such as load-bearing mechanical structures, components for kilns or similar arrangements with high thermal stress etc. by varying the parameters The achievable strength of the method according to the invention is also the same Extensibility of the deposited layer over a relatively wide range adjustable, as will be explained in more detail in the further text.

• mindestens eine konturierte Anode, deren Kontur an die Kontur eines Abscheidungskörpers angepasst ist,
• eine Einrichtung zur Ansteuerung der Anode und der Kathode des Bades mit periodischen Strompulsen,
• Stromblenden zur zumindest teilweisen Abschirmung des Abscheidungskörpers,
• eine Filtereinrichtung zur Filterung des Elektrolyten und
• eine Umwälzeinrichtung zur Umwälzung des Elektrolyten, aufweisend mindestens eine Umwälzpumpe und Düsen zur Rückführung des Elektrolyten in das Bad.

Another object of the invention is a special galvanic bath for the electrodeposition of nickel or nickel alloys or cobalt or cobalt alloys with an electrolyte

• at least one contoured anode, the contour of which is adapted to the contour of a deposition body,
• a device for controlling the anode and the cathode of the bath with periodic current pulses,
• Current shutters for at least partially shielding the deposition body,
• a filter device for filtering the electrolyte and
• a circulating device for circulating the electrolyte, comprising at least one circulating pump and nozzles for returning the electrolyte into the bath.

This special galvanic bath can be used to implement special training of the aforementioned method can be used. The above In principle, however, the process can also be carried out in other galvanic designs Baths can be realized that are suitable to the basic invention Procedure or one of its further training are adapted.

The further design of this special bath can be done by a corresponding Adaptation to the features of the description above the method according to the invention take place. For example, it can be provided be that the at least one contoured anode is contoured Container is formed with bodies made of nickel or cobalt or a nickel alloy or a cobalt alloy can be filled.

As already stated, it can in particular be provided that several anodes are arranged in the bath, only that of the deposition body closest anodes are designed as contoured anodes are. This means that of course the other anodes also have a certain one Have a contour, but in this case only the contour of those should Anodes that are closest to the deposition body to the contour of the Separator body to be adjusted. The contouring can only be in a spatial direction e.g. in the longitudinal direction of the anode, or it can also take place in more than one spatial direction, e.g. additionally perpendicular to Longitudinal direction.

Furthermore, the cleaning device can be a filter device, in particular an activated carbon filter, and a selective bath. This allows both Suspended particles suspended in the electrolyte as well as unwanted particles Foreign elements are removed from the electrolyte.

A specific embodiment of the present invention is as follows described with reference to Figures 1 to 3.

Fig. 1:

Abhängigkeit der Festigkeit und Dehnbarkeit der abgeschiedenen Schicht von dem Ladungsverhältnis Q_A/Q_C im erfindungsgemäßen Bereich des Stromdichtenverhältnisses I_A/I_C

Fig. 2:

Aufbau eines erfindungsgemäßen Bades

Fig. 3:

Draufsicht auf eine spezielle Ausgestaltung eines erfindungsgemäßen Bades.

Show it:

Fig. 1:

Dependence of the strength and extensibility of the deposited layer on the charge ratio Q _A / Q _C in the range of the current density ratio I _A / I _C according to the invention

Fig. 2:

Structure of a bath according to the invention

Fig. 3:

Top view of a special embodiment of a bathroom according to the invention.

The process according to the invention is described in the following example a galvanic bath with an electrolyte is provided, which nickel compounds contains. Basically, a galvanic bath is also included Cobalt compounds conceivable. For this, according to the from the Electrolytes known as prior art as nickel compounds or cobalt compounds for example nickel sulfate and nickel chloride or also nickel sulfamate and nickel chloride are provided, as well as in the case of the cobalt compounds the corresponding sulfates, sulfamates or chlorides. To the special possibilities of the composition of the electrolyte is on the prior art cited at the beginning. There can also be additional ones Additives may be provided in the electrolyte, such as that in the EP 0 835 335 or DE 22 18 967 cited sulfonated naphthalene or those in US 2,470,775 column 3 paragraph 2 additives mentioned.

The so-called pulse plating method is now used for the deposition applied, i.e. the application of anodes and cathodes to the bath with periodic current pulses, which in principle come from the state cited at the beginning is known in the art. There are wide parameter ranges from who the special settings for the procedure, especially for the Choice of current densities and pulse durations can be selected. It has it turned out, however, that with such parameter values a weldability the electroplated layer can not be achieved because the layers deposited in this way do not meet the necessary requirements Have strength and elasticity.

These necessary strengths can only be achieved if the ratio I _A / I _C of anode current density I _A to cathode current density I _{C is} chosen to be greater than 1 and less than 1.5 and the charge ratio Q _A / Q _C = (T _A · I _A ) / (T _C · I _C) of the transported during an anode pulse of the duration T _a charge Q _a is to be transported during a cathode pulse of the duration T _C charge Q _C between 30 and 45, better results being obtained when the ratio I _A / I _{C is} between 1.2 and 1.45 and the best results are obtained for a ratio between 1.3 and 1.4, the charge ratio Q _A / Q _C = (T _A · I _A ) / (T _C · I _C ) is in each case between 35 and 40. It has thus been found that no arbitrary choice of the ratios I _A / I _C and Q _A / Q _C may be made in order to achieve the desired advantageous properties of the deposited layer, but that these only apply to a certain range of values for the ratio I _A / I _C and a coupled range of values for the ratio Q _A / Q _{C is} given. This is especially true for the aforementioned value ranges.

For this purpose, reference is made to FIG. 1, which shows the dependence of the yield strength (0.2 yield strength) R _{p 0.2} , the strength R _m and the ductility A _{5 of} a nickel layer deposited according to the aforementioned method on the charge ratio Q _A / Q _C for current density ratios I _A / I _C between 1.3 and 1.4 describes. It is shown here that with a charge ratio between 35 and 40 the strengths and the extensibility are in a medium range of values, ie an optimal balance is found between the extensibility and strength of the deposited layer. If the charge ratio is increased, the ductility continues to increase, but at the same time the strength continues to decrease, so that the deposited layer does not have sufficient mechanical stability. If, on the other hand, the charge ratio is further reduced, the strength increases, but the ductility decreases significantly, which means that the deposited layer becomes very brittle and especially in the area of weld seams in which there is material shrinkage during welding and therefore thermomechanical stress on the layer occurs, there is a risk of material breakage. Even if the current density ratio is increased or decreased, the values become correspondingly less favorable. An analogous behavior is expected for cobalt and cobalt alloys.

2 schematically shows the structure of the bath for realizing the invention, which is filled with an electrolyte as described above. there there is a deposition body 2 such as a combustion chamber a rocket engine in a bath 1. On this deposition body a coating is now to be generated, for example, from nickel. For this purpose, at least one anode 3 is let into the bath 1, the Anode 3 is contoured in such a way that it conforms to the contour of the deposition body 2 is adjusted. The contouring can only be in one spatial direction e.g. in the longitudinal direction of the anode 3, or it can also be in more be provided as a spatial direction, e.g. additionally perpendicular to the longitudinal direction. 2 shows only a single anode 3 for the sake of simplicity shown. 3 shows a possible arrangement of several anodes 3a, 3b in a bath 1, being those anodes 3a that the deposition body are closest, as contoured anodes are formed, because the positive influence of contouring is most noticeable there. The anodes 3b further away, on the other hand, can be used as universal in the simplest case, flat anodes are formed, for which each standardized anode shape is applicable. Consequently, only those of the deposition body 2 closest anodes 3a to the adapt special shape of different deposition body 2. This anode concept provides an optimization of the effect of the anodes 3a, 3b at the same time maintaining an arrangement that is as universal as possible.

The contoured anode 3 in FIG. 2 is formed by a contoured container 8, which is designed for example as a titanium basket and therefore permeable is for the nickel ions necessary for the deposition. The container 8 can also additional sheaths that are also permeable to nickel ions be surrounded by a bag, for example. The nickel is here introduced in the form of small nickel bodies 9 in the container 8 and can in a simple way with a gradual consumption of nickel during of the deposition process can be easily refilled. about a device 4 controls the anode 3 and the cathode acting deposition body 2 in the bath 1 with periodic current pulses to carry out the pulse plating process described.

Current diaphragms 5 are also provided, which at least during one Part of the deposition process certain areas of the deposition body Shield 2. In the case of Fig. 2, the edges of the deposition body 2 shielded, as increased separation in these areas without shielding of nickel would occur and so an inhomogeneous deposition would take place over the entire deposition body 2. Here they would be Current diaphragms 5 are provided as rings that are concentric around the edge areas of the deposition body 2 are arranged. Through the current shields 5 can at least shield these areas for a period of time be seen so that a more homogeneous over the entire deposition time Deposition over the entire deposition body 2 can be achieved can. In another form of the deposition body 2, the appropriate areas are shielded, in which an increased separation such as surveys. Otherwise one can less separation in other areas such as deepening be balanced. The current diaphragm 5 can for example in the bathroom 1 slidably or completely removable, for what suitable facilities must be provided.

Before deposition, it makes sense to clean the electrolyte. This can be done in particular with the help of activated carbon in a concentration from preferably 1 g / l to 3 g / l and with 30% hydrogen peroxide in a concentration of preferably 1 ml / l to 2 ml / l, with higher ones also or lower concentrations are basically possible.

A cleaning device 6 is used to clean the electrolyte from interfering Foreign elements and floating particles during the deposition process and takes place with the help of activated carbon filters 10 and a selective bath 11, shown only schematically in FIG. 2. The removal and return of the electrolyte into the bath is carried out by appropriate supply and discharge lines. This enables a particularly high purity of the electrolyte and its almost complete liberation of foreign elements, especially foreign metals, as well as from suspended particles. It can through this Part of the process, in particular the proportion of foreign elements Fe, Cu, Cr, Al, Zn, Co in the nickel bath can be reduced to values below 0.1 mg / l, which the properties of the deposited layer also benefit because through such a reduction in the proportion of foreign elements, the extensibility the deposited layer is further improved and an additional one guaranteed high or even higher strength of the deposited layer.

The bath also has a circulating device shown schematically in FIG. 2 13 for circulation of the electrolyte, which from a circulation pump 12 and suitably designed and suitably arranged nozzles 7 for There is recycling of the electrolyte. Just the return to the bathroom in this form with the help of nozzles 7 can also be used for a To promote circulation of the electrolyte in the bath 1 and the other hand To supply electrolytes specifically to the deposition body 2. The right one The arrangement and alignment of the nozzles 7 should be selected so that these specifications be fulfilled. In principle, the cleaning device 6 could also and the circulating device 13 can be combined in a single device, for example by recycling the in the cleaning device 6 cleaned electrolytes into the bath 1 using nozzles 7.

Claims (19)

Process for the electrodeposition of nickel, cobalt, nickel alloys or cobalt alloys in a galvanic bath (1) using an electrolyte containing nickel compounds or cobalt compounds, with at least one anode (3, 3a, 3b) and at least one cathode of the bath (1) for the deposition periodic current pulses are applied, characterized in that the ratio I _A / I _C of anode current density I _A to cathode current density I _{C is selected to be} greater than 1 and less than 1.5 and the charge ratio Q _A / Q _C = (T _A · I _a) / (T _C · I _C) of the transported during an anode pulse of the duration T _a charge Q _a is to be transported during a cathode pulse of the duration T _C charge Q _C between 30 and 45. A method according to claim 1, characterized in that the ratio I _A / I _{C is} between 1.2 and 1.45, in particular between 1.3 and 1.4 and the charge ratio Q _A / Q _C = (T _A · I _A ) / (T _C · I _C ) is between 35 and 40. Method according to one of claims 1 or 2, characterized in that at least one contoured anode (3, 3a, 3b) is used for the deposition, the contour of which is adapted to the contour of a deposition body (2) on which the nickel or cobalt or the Nickel alloy or cobalt alloy is to be deposited. Method according to Claim 3, characterized in that a plurality of anodes (3a, 3b) are provided in the bath (1) and a contoured anode (3a) for at least one of the anodes (3a) which are arranged closest to the deposition body (2) ) is used. Method according to one of claims 3 or 4, characterized in that a contoured container (8) is used to form the contoured anode (3a), which is permeable to the nickel to be deposited or the cobalt or the nickel alloy or the cobalt alloy and which has bodies (9) is filled from nickel or cobalt or a nickel alloy or cobalt alloy. Method according to one of claims 3 or 4, characterized in that a solid electrode body is used as the contoured anode (3, 3a, 3b), which has at least one coating of the nickel or cobalt to be deposited or the nickel alloy or cobalt alloy to be deposited. Method according to one of claims 1 to 6, characterized in that the deposition body (2) is partially shielded by current diaphragms (5) at least during part of the total deposition time. A method according to claim 7, characterized in that the flow orifices (5) are arranged in those areas of the deposition body (2) in which a preferred deposition takes place. Method according to one of claims 1 to 8, characterized in that the electrolyte is cleaned before the start and / or during the deposition. A method according to claim 9, characterized in that 0.5 g / l to 5 g / l, in particular 1g / l to 3g / l activated carbon and 0.5 ml / l to 3 ml are used for cleaning the electrolyte before the deposition begins / l, in particular 1ml / l to 2ml / l 30% hydrogen peroxide can be used. Method according to one of claims 9 or 10, characterized in that for cleaning the electrolyte during the deposition, the electrolyte is filtered, in particular with the aid of at least one activated carbon filter (10), and foreign elements are removed from the electrolyte with the aid of at least one selective bath ( 11) takes place. Method according to one of claims 1 to 11, characterized in that at least part of the deposition time, the electrolyte is circulated with the aid of at least one circulating device (13) and the electrolyte is returned to the bath (1) by means of nozzles (7) , A method according to claim 12, characterized in that the nozzles (7) are designed and arranged in the bath (1) in such a way that circulation of the bath (1) and / or flow of the electrolyte directed towards the deposition body (2) is achieved , Use of a method according to one of claims 1 to 13 for the manufacture of components for rocket engines. Use of a method according to one of claims 1 to 13 for the production of injection heads and / or combustion chambers and / or Thrusters for rocket engines. Galvanic bath (1) for the galvanic deposition of nickel or Comprising nickel alloys or cobalt or cobalt alloys with an electrolyte at least one contoured anode (3, 3a, 3b), the contour of which is adapted to the contour of a deposition body (2), a device (4) for controlling the anode (3) and the cathode (2) of the bath (1) with periodic current pulses, Current diaphragms (5) for at least partially shielding the deposition body (2), a cleaning device (6) for cleaning the electrolyte and a circulating device (13) for circulating the electrolyte, comprising at least one circulating pump (12) and nozzles (7) for returning the electrolyte into the bath. Galvanic bath according to claim 16, characterized in that the at least one contoured anode (3, 3a, 3b) is designed as a contoured container (8) which can be filled with bodies (9) made of nickel or cobalt or a nickel alloy or a cobalt alloy. Galvanic bath according to one of claims 16 or 17, characterized in that a plurality of anodes (3a, 3b) are arranged in the bath (1), only the anodes (3a) closest to the deposition body (2) being designed as contoured anodes , Galvanic bath according to one of claims 16 to 18, characterized in that the cleaning device (6) includes a filter device (10) and a selective bath (11).

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