DE3840310A1 - Method for accelerated deposition of a thick reconditioning layer on a worn workpiece - Google Patents

Abstract

Method for accelerated electrochemical deposition of a thick reconditioning layer on a worn or damaged workpiece (9), using an insoluble anode and an electrolyte (1) which is guided as a flow against the surface to be coated, a current density of at least 10 A/dm<2> being employed at the point of application of the workpiece (9) connected as the cathode, and the electrolyte (1) being vigorously agitated mechanically at this point, and the metallic layer (14) already deposited being mechanically affected by gentle rubbing/stroking with a porous soft medium (15) in which abrasive particles are embedded. Use for reconditioning of used (worn) turbine blades made of nickel-based superalloys. <IMAGE>

Description

Technical area

Renewal and repair of worn and damaged Components of thermal machines, in particular of steam and gas turbine blades. Applying thick layers on the components.

The invention relates to the restoration of original shape of a component of a thermal machine, which in operation no longer permissible form Wear, erosion, corrosion, oxidation, mechanical loading damage, etc.

In particular, it relates to a method of accelerated Applying a thick renewal layer on a as Turbine component present worn and / or damaged Workpiece with the aid of an electrochemical Pro with an insoluble anode, with one to be applied Elements in ionic form containing electrolyte as a stream against the surface to be coated of the workpiece ge is pressed.  

State of the art

The application of surface layers of any kind Machine components plays in the modern technology, in particular This is an important factor in the construction and operation of thermal machines Role.

It is known that in used or damaged door bin parts such as - housing, shovels, etc. - the eroded or crumpled places with a thick order of Be renewed metals or metal-like material.

Such repairs have so far depending on the nature of the load - whether by temperature, corrosion or Ero sion - by means of welding, spraying or gluing performed. The application of thick layers by these mentioned methods can be carried out in a relatively short time. However, the quality of such coatings very often brings deficiencies in terms of adhesion to the base material, as well as structural changes by inherent internal stresses (cracking) with it.

Numerous methods are known in the art, surfaces layers on galvanic (electrolytic, electrochemical) Ways to a mostly metallic or previously suitable Way pretreated to apply (metallized) substrate. These are usually relatively thin, from fractions of microns to a few tenths of a milli meters reaching layers. Because of their limited thickness Such layers are usually characterized by good adhesion strength and sufficient abrasion resistance against their Base (substrate) off. On the other hand, their use is limited to those cases where their limited Dimension perpendicular to the surface the operational requirements and where not changes or even zer disturbances due to diffusion processes during operation to be feared.  

From the electroplating process are known that ge equip objects with electrochemical processes locally selectively coat. Among them fall under derem the so-called surge, tampon and nozzle flow method. This is either a surge or a Strö tion of the electrolyte targeted to the scarf as a cathode addressed to the object to be coated or the latter is obtained by local painting with one of the Wetted electrolyte (see Sauter, "Fundamentals of Selective Plating", Galvanotechnik 76, 1985, No. 12, pp. 1950-1951, D-7968 Saulgau; M. Rubinstein, "Tampon Plating", Eugen G. Leuze Verlag, 1985, D-7968 Saulgau).

For the achievement of the above purpose of the new tion and maintenance of workpieces have the well-known Process a number of shortcomings:

The dipping process (normal electroplating in an electrolyte) can only be carried out at low current densities (0.5-2A / dm ² ), which means correspondingly low application rates (on average 6-12 μm / h, at most 24 μm / h for nickel). entails. It is a cover ("masking") of the surfaces not to be coated necessary. Therefore, this method is limited to small objects.

In the "tampon" (wiping, wetting) method are only simple geometrical shapes of the workpiece possible, the manual effort for soaking the "tampons" is considerable. Mechanization is complicated Forms of the workpiece not feasible.

The spraying of the electrolyte in the "flood / jet" method leads to a very irregular flooding of the factory piece, with a preferred metal deposition at corners and edges takes place. The ion transport in the cathode  is the closest diffusion zone in the electrolyte bad. This results in excessively high current densities the anode. For insoluble anodes is a high cost if necessary, massive precious metal (platinum) is required a premature destruction of a merely platinized Anode is accepted. For soluble anodes result irregularities due to periodic passivation ("Pump" -) appearances, crumbling, bud formation, short conclusions, etc. There is a strong oxygen separation on the anode surface with the formation of unwanted Oxides and a chemical electrolyte breakdown together setting. At the cathode (workpiece) results in a high Hydrogen evolution with dimpling and warts in the applied layer.

It is clear from the above that it is a strong one There is a need to eliminate the above defects as far as possible and to further develop and extend the existing procedures improve. Here is the galvanic application of thick Layers are in the foreground.

Presentation of the invention

The invention has the object of providing a way up show and indicate means, such as a used one, by Wear, erosion, corrosion, oxidation, mechanical damage damage in its form, in particular its Oberflächenge During the operation changed turbine component renewed, repaired and in the fully functional condition can be brought. It should be the newly applied Surface layer due to solid adhesion and good chemical physical compatibility with the existing one Mark core (substrate). Furthermore, the renewed Component due to freedom from cracking and damaging, in operation to undesirable chemical-physical (metal lurgical) changes leading diffusion.  

This object is achieved in that in the above erwähn th process is acted upon by the acted upon by the electrolyte deposition point of the cathode connected to the workpiece with a current density of at least 10 A / dm ² , and that the body wetting this point mechanically moves strongly and the This point on the workpiece already applied metallic layer simultaneously during or immediately after application by light rubbing or brushing with a porous soft medium in which abrasive particles are embedded, is mechanically affected.

Way to carry out the invention

The invention will be described with reference to the following figures described embodiments described.

Showing:

Fig. 1 shows the schematic structure of a plant for carrying out the electrodeposition coating method,

Fig. 2 is a section through part of the apparatus for performing the deposition process with tampon and smoothing means in the form of a "train",

Fig. 3 is a section through part of the apparatus for performing the deposition process with smoothing means in the form of "sponges"

Fig. 4 shows a section through a part of the apparatus for performing the application process with electrolyte inflow through the smoothing agent in the form of "Schwäm men".

In Fig. 1 the schematic structure of a plant for the implementation of the galvanic application process is shown. 1 is the electrolyte, which is supplied via an electrolyte line 2 by means of a circulation pump 3 a funnel 5 . The latter is mounted in a support rod 6 , which in turn is mounted slidably in two directions in the horizontal plane (vertical plane perpendicular to the plane of the drawing) (not shown): The possibility of movement is interpreted by arrows. A trough 4 (electrolyte vessel) serves to catch the flowing-down electrolyte 1 and to return it via the circulating pump 3 . After leaving hopper 5, electrolyte 1 flows through a plastic fleece 8 (tampon) containing abrasive particles into which a platinum wire coil 7 serving as an anode is embedded. The cathode as we kende workpiece 9 is clamped in the workpiece holder 10 and connected to it non-positively and electrically conductive. The electrolyte 1 wets and flows around the workpiece 9 in the immediate vicinity of the plastic fleece 8 and then flows or drips into the tub 4 . The abrasive particles of the plastic fleece (tampon) continuously smooth the surface of the workpiece 9 to be coated during the reciprocating movement.

Fig. 2 shows a section through a part of the apparatus for performing the application method with tampon and Glät processing means in the form of a "train". 1 is the electrolyte in a feed channel 12 to the plastic non-woven 8 and the anode as the +/- pole of a current source connected Platindrahtwendel 7 is passed. The Elektrolytzufluß 11 is indicated by a vertically downward arrow. The lateral mobility of the feed channel 12 in the horizontal plane is marked by horizontal arrows mar. The Elektrolytzufluß 11 is controlled so that the web 8 is completely saturated and below it forms a permanent electrolyte column 13 between the anode and cathode, which completely wets the lying directly in the vicinity of the workpiece part 9 . The approximate limitation of the electrolyte column 13 is indicated by a dashed line. The plastic fleece 8 ent holds abrasive particles (abrasive), indicated by dots. It ends in a trained as a smoothing part, the "train" 15 on the surface of the workpiece 9 and derived. In this case, both its original surface as well as the metal layer 14 applied immediately before it are smoothed and kept clean.

In Fig. 3 is a section through a part of the apparatus for performing the application method with smoothing agent in Fom of "sponges" is shown. The middle part of the device corresponds to Fig. 2 except for the "train" 15 , which is missing here. The electrolyte 1 successively flows through the supply channel 12 , the platinum wire coil 7 and the plastic nonwoven fabric 16 (tampon), which contains no abrasive particles here Chen. The smoothing and cleaning of the surface of the workpiece 9 and the applied metallic layer 14 is performed by the "sponges" 17 arranged on both sides of the electrolyte inflow 11 or the electrolyte column 13 . The latter consist of a plastic fleece with embedded abrasive particles. The "sponges" 17 sit in vertically freely movable tubes 18 , which in turn are mounted in horizontally displaceable guide sleeves 19 . This ensures optimum adaptation to the unevenness of the applied metallic layer 14 and thus best cleaning and smoothing. The possibilities of movement are indicated by arrows.

Fig. 4 shows a section through part of the device for carrying out the application process with electrolyte flow through the smoothing agent in the form of "sponges". The arrangement is similar to that of Fig. 3, but the middle part is completely absent. 1 is the electrolyte, 13 the electrolyte column between anode and cathode. The Elektro lytzufluß 11 is carried out by one in a guide sleeve 19 vertically movable platinum tube 20 , which is connected as an anode to the +/- pole of the power source. The guide sleeves 19 are displaceable in the horizontal plane. The plastic fleece sponges 17 contain abrasive particles. The platinum tubes 20 may be replaced by platinum tubes of suitable conductive material.

Embodiment 1

See Figs. 1 and 2! As a workpiece 9 was a worn, partially damaged at its upper half of the blade gas turbine blade. The blade blade had the following dimensions:

Length | 175 mm Largest width 88 mm Biggest thickness 22 mm profile height 28 mm

The gas turbine blade consisted of an oxide dispersion hardened Superalloy with the following composition:

Cr 17.0% by weight al 6.0% by weight Mo 2.0% by weight W 3.5% by weight Ta 2.0% by weight Zr 0.15% by weight B 0.01% by weight C 0.05% by weight Y₂O₃ 1.1% by weight Ni rest

The workpiece 9 was first subjected to a pretreatment:

• - Electrolytic degreasing in a commercially available degreasing bath:
  Current density: 10 A / dm²
  Temperature: 40 ° C
  Time: 30 sec cathodic operation
  15 sec anodic operation
• - Etching in HCl solution (concentrated HCl: H₂O = 1: 1):
  Current density: 10 A / dm²
  Temperature: 20 ° C
  Time: 45 sec anodic farms
• - Neutralize:
  Time: 30 sec cathodic operation,
  15 sec anodic operation
• - etching:
  Time: 5 sec anodic operation
• - Pre-nickel in a bath of the following composition:
  300 g / l NiCl₂ · 6 H₂O
  60 ml / l concentrated HCl
  Time: 3 sec anodic operation (etching)
  1 min cathodic operation (pre-nickel-plating)

Now, the pre-nickel-plated workpiece 9 was clamped in the workpiece holder 10 and coated by the method according to the invention with an approximately 1.5 mm thick nickel layer. The operating conditions were as follows:

Bath composition:
700 g / l nickel sulfamate
5 g / l NiCl₂ · 6 H₂O
30 g / l H₃BO₃
Remainder H₂O

Virtual average current density: 80 A / dm²
Temperature: 70 ° C
Application speed: 50 μm / h
Duration: 30 h

The funnel 5 or the feed channel 12 for the electrolyte 1 fastened in the horizontally displaceable holding rod 6 was constantly moved slowly back and forth during the electrochemical application process. In this case, the upper surface of the workpiece 9 or the already applied metallic layer 14 was continuously smoothed and cleaned by the "train" 15 of plastic fleece with abrasive particles. As a result, hydrogen bubbles and protruding dendrites were constantly removed and neither dimples nor "buds" or warts could form on the surface of the supported layer 14 .

After nickeling, the workpiece 9 was rinsed and net getrock. The applied nickel layer showed no cracks or pores.

Embodiment 2

See Figs. 1 and 3!
The workpiece 9 consisted of an airfoil of a head-end damaged gas turbine blade having the following dimensions:

Length | 160 mm Largest width 78 mm Biggest thickness 20 mm profile height 27 mm

The workpiece 9 was made of an oxide-dispersion-hardened nickel-base superalloy with the trade name MA 6000 from INCO and had the following composition:

Cr 15% by weight W 4.0% by weight Mo 2.0% by weight al 4.5% by weight Ti 2.5% by weight Ta 2.0% by weight C 0.05% by weight B 0.01% by weight Zr 0.15% by weight Y₂O₃ 1.1% by weight Ni rest

The workpiece 9 was subjected to the same pretreatment as in Example 9. Then the pre-nickel-plated workpiece 9 was clamped in the workpiece holder 10 and coated with an approximately 1.8 mm thick nickel layer, in the same time chromium in the form of particles of chromium carbide Cr ₃ C _{2 was} stored. The Cr ₃ C ₂ particles were added to the electrolyte 1 in the form of a suspension. For applying the device of FIG. 3 was used. The operating conditions were as follows:

Bath composition:
380 g / l of 5-sulfosalicylic acid
192 g / l NiCO₃

Virtual average current density: 30 A / dm²
Cell voltage: 6V
Temperature: 40 ° C
Application speed: 150 μm / h
Duration: 12 h
Chromium carbide particles: 30 g / l
Particle diameter: 10-50 μm

During the application process, the funnel 5 or the feed channel 12 for the electrolyte 1 and the "sponge" 17 consisting of plastic non-wovens with abrasive particles or the guide sleeves 19 were constantly moved back and forth. The effect was the same as given in Example 1. The applied Cr ₃ C ₂ doped nickel layer had neither pores nor cracks.

Embodiment 3

See Figs. 1 and 4!
As workpiece 9, there was a damaged gas turbine blade with the following dimensions of the airfoil:

Length | 185 mm Largest width 94 mm Biggest thickness 23 mm profile height 30 mm

The workpiece 9 was made of a nickel-base cast superalloy with the trade name IN 738 of INCO and the following composition:

Cr 16.0% by weight Co 8.5% by weight Mo 1.75% by weight W 2.6% by weight Ta 1.75% by weight Nb 0.9% by weight al 3.4% by weight Ti 3.4% by weight Zr 0.1% by weight B 0.01% by weight C 0.11% by weight Ni rest

After the pretreatment of the workpiece 9 according to Example 1, this was clamped in the workpiece holder 10 and coated with an approximately 2 mm thick nickel layer. To carry out the application, the device according to FIG. 4 was used. The operating conditions were the following:

Bath composition:
200 g / l NiSO₄ · 7 H₂O
100 g / l (NH₄) ₂ SO₄
60 g / l CoCl₂ · 6 H₂O
NH₄OH to pH = 8.5

Virtual average current density: 225 A / dm²
Cell voltage: 7V
Temperature: 50 ° C
Application speed: 250 μm / h
Duration: 8 h

About the supply of the electrolyte 1 and the movement of the "sponges" 17 Fig. 4 information. Platinum tubes 20 were used for the anodic current conduction. The applied nickel / cobalt layer was smooth and free of pores.

The invention is not exhausted in the embodiments. The acted upon by the electrolyte 1 applied job of the switched as a cathode workpiece 9 current density is at least 10 A / dm ² , wherein the electrolyte 1 is mechanically moved at this point. The metallic layer 14 already applied here is simultaneously or during the application by light rubbing / brushing with a porous soft medium 15 ; 17 mechanically influenced. The rubbing or brushing medium contains embedded abrasive particles which clean and smooth the surface. The Elektrolytzufluß 11 is carried out either at a single point, at which the same time the mechanical influence of the surface is taken, with a designed as a train 15 extension of acting as a tampon absorbent, doped with abrasive particles plastic fleece 8 is used, or there are separate items after the task. In this case, the Elektrolytzufluß 11 takes place to a non-abrasive particles doped plastic fleece 16 , while the separately arranged doped plastic nonwovens 17 take over the cleaning. Another possibility is in Elektrolytzufluß 11 at several points, the do-oriented plastic nonwovens 17 serve simultaneously to transfer the electrolyte 1 to the surface of the workpiece 9 as to its mechanical influence.

The advantages of the method are:

• - Crack and pore-free dense surface layer also at thick coatings (several millimeters).
• - No warts, buds and pits.
• - No change in the electrolyte.
• - High cathodic current density.
• - Comparatively short duration of the metallic application.

Claims (4)

1. A method for accelerated application of a thick He innovierungsschicht on a turbine as vorlie ing ing worn and / or damaged workpiece ( 9 ) with the aid of an electrochemical process with insoluble anode, wherein the elements to be applied Ele in ionic form containing electrolyte ( 1 ) as a current against the surface of the workpiece ( 9 ) to be coated is pressed, characterized in that at the applied by the electrolyte ( 1 ) application point of the cathode connected to the workpiece ( 9 ) is driven with a current density of at least 10 A / dm ² , and that the this passage wetting electrolyte (1) mechanically strong moved and at this point on the workpiece (9) already deposited metallic layer (14) simultaneously during, or immediately after application by gently rubbing or brushing with a porous soft medium (15; 17 ), in which abrasive particles are embedded, mechanically being affected. 2. The method according to claim 1, characterized in that the electrolyte ( 1 ) in the form of a stream in a supply channel ( 12 ) zugleitet a tampon of an absorbent plastic non-woven ( 8 ) and of this via at least one as a train ( 15 ) designed extension locally on the surface of the workpiece to be coated ( 9 ) will wear, the train ( 15 ) continuously over the workpiece ( 9 ) back and forth and the freshly applied metallic layer ( 14 ) permanently with the train ( 15 ) coated and wetted with fresh electrolyte ( 1 ). 3. The method according to claim 1, characterized in that the Elektrolytzufluß ( 11 ) is accomplished separately via a non-abrasive particles doped plastic nonwoven fabric ( 16 ) as a tampon and that the mechanical influence of the surface of the workpiece ( 9 ) and the already applied metallic layer ( 14 ) by separate, vertically freely movable, horizontally forcibly with the tampon ( 16 ) reciprocating, as a sponge ( 17 ) formed with abrasive particles plastic nonwovens takes place. 4. The method according to claim 1, characterized in that the Elektrolytzufluß ( 11 ) via at the same time the mechanical rule influencing the surface of the workpiece ( 9 ) and the already applied metallic layer ( 14 ) serving as a sponge ( 17 ) formed with abrasive particles Plastic nonwovens takes place, which are freely movable vertically, horizontally forcibly be moved back and forth.