Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
  • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/04—Electroplating: Baths therefor from solutions of chromium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/20—Electroplating: Baths therefor from solutions of iron
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/22—Electroplating: Baths therefor from solutions of zinc
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/26—Electroplating: Baths therefor from solutions of cadmium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/46—Electroplating: Baths therefor from solutions of silver
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/48—Electroplating: Baths therefor from solutions of gold
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/54—Electroplating of non-metallic surfaces
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/615—Microstructure of the layers, e.g. mixed structure
  • C25D5/617—Crystalline layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated
  • C25D7/003—Threaded pieces, e.g. bolts or nuts

Definitions

• the present invention relates to a method for producing galvanically coated components.
• an edge layer of a component to be coated is subjected to a mechanical treatment in which the edge layer is deformed at least in sections, whereby the structure of the edge layer is modified at least in sections and hydrogen traps are generated in the modified sections of the edge layer.
• a coating is electrodeposited at least on part of the surface of the mechanically treated edge layer of the component to be coated, hydrogen being released during the electrodeposition, which at least partially penetrates into the mechanically treated edge layer.
• the hydrogen traps produced in the modified sections of the edge layer essentially bind all of the penetrating into the mechanically treated edge layer during the galvanic deposition in step b) Hydrogen.
• the present invention also relates to a component that can be produced using the method according to the invention and the use of such a component.
• the galvanic coating of components with the purpose of protecting against corrosion or wear is in many cases indispensable and often the last step in component production processes. Due to the electrochemical principles of electroplating processes, atomic hydrogen is always released as a by-product. Under certain boundary conditions, atomic hydrogen can easily penetrate into the material to be coated and there, for example in high-strength steels, but also in many other metallic alloys, can lead to the feared hydrogen embrittlement. Hydrogen embrittlement can manifest itself in a delayed, unexpected component failure, or in failure well below the elongation or strength limit, or in the case of a reduced number of alternating loads (vibration stress).
• Shot peening is a typical process. Shot peening before galvanic coating is preferably used on components subject to vibrations and is not restricted to rotationally symmetrical geometries. It has found widespread use in the aviation sector and is mandatory there for high-strength, hard-chrome-plated components. In the EP 1 920 088 A shot peening process for already coated components was also reported, which also pursues the goal of generating favorable residual stresses in the layer.
• step a) of the method according to the invention a pretreatment of the component to be electroplated is carried out before the electroplating.
• an edge layer of the component to be coated is subjected to a mechanical treatment.
• An edge layer is understood to mean a layer-shaped region of the component which is located at the edge of the component and preferably runs essentially parallel to the edge of the component.
• the surface layer is deformed at least in sections.
• the aim of the mechanical treatment used in step a) according to the invention is to determine the structure of the surface layer, i.e. to modify the atomic structure or the crystal structure of the material in the edge layer, at least in sections. In other words, the atomic structure or the crystal structure in the boundary layer changes at least in sections.
• the structural modification can include grain refinement, an increase in dislocation density (i.e. increase in the density of disturbances in the ordered crystal structure), and / or the emergence of slip steps (shear in or between grains).
• dislocations can occur during the structural modification, i.e. Defects in the atomic structure or the crystal structure.
• Hydrogen traps are generated in the modified sections of the edge layer by the mechanical treatment or the at least sectionally deformation in step a).
• Hydrogen traps are special structural elements in the atomic structure or the crystal structure of a material in which hydrogen, preferably permanently, can be bound. Hydrogen traps primarily include dislocations, grain boundaries (grain refinement, formation of grain twins), slip levels and other changes or modifications in the atomic structure or crystal structure caused by the at least partial deformation.
• hydrogen traps can also arise, for example, from transformations of metastable states, for example in steel: residual austenite to martensite. The ability of hydrogen traps to trap hydrogen to bind can be quantified by their binding energy. For this purpose, the material is heated and the temperature at which the trap releases the hydrogen is observed.
• the at least partial modification of the structure of the edge layer can also be accompanied by at least partial solidification of the edge layer.
• Such hardening is used in metalworking and metalworking to denote a change in material that leads to increased strength or increased hardness, which can be achieved by means of technological tests, among other things. is demonstrable as an increased resistance to permanent deformation.
• Common methods for determining hardness are hardness tests according to Vickers (DIN EN ISO 6507) or Rockwell (DIN EN ISO 6508).
• step b) the galvanic coating of the component pretreated in step a) takes place.
• a coating is electrodeposited at least on part of the surface of the mechanically treated edge layer of the component to be coated.
• hydrogen is released, which at least partially penetrates into the mechanically treated surface layer.
• the hydrogen traps generated in the modified sections of the boundary layer essentially bind all of the hydrogen that penetrates into the mechanically treated boundary layer during the electrodeposition in step b).
• the concentration of the (atomic and / or molecular) hydrogen present in the electroplated component, which is not bound in the hydrogen traps at most 2 ppm, preferably at most 1 ppm, particularly preferably at most 0.5 ppm, is.
• the concentration of diffusible hydrogen in the material volume is preferably at most 2 ppm, more preferably at most 1 ppm, particularly preferably at most 0.5 ppm.
• the fact that the hydrogen traps generated in the modified sections of the boundary layer essentially bind all of the hydrogen entering the mechanically treated boundary layer during the electrodeposition in step b) can be achieved in that the total volume of the hydrogen traps generated in step a) is large enough, in order to bind the amount of hydrogen penetrating into the mechanically treated surface layer during the electrodeposition in step b).
• This total volume of the hydrogen halls can be influenced by the mechanical treatment in step a). The exact implementation of such an influence depends on the chosen form of mechanical treatment. If the mechanical treatment is carried out, for example, by shot peening, the parameters of the shot peening treatment are selected, for example, in such a way that a sufficient dislocation density is produced down to sufficient depths.
• Usual, available beam parameters are, for example, the diameter of the shot balls, the speed of the hit balls and the shot time.
• the mechanical treatment is carried out, for example, by deep rolling, it can be influenced, for example, by varying the radius of the deep rolling tool, the contact pressure, the overlap of the rolling tracks and the number of rollovers.
• the mechanical treatment is carried out, for example, by machining (such as grinding, turning, milling), the cooling conditions, the sharpness of the cutting elements and suitable combinations of infeed and feed can influence, such as preferred, deformation resulting in increased dislocation densities.
• Optimal treatment or processing parameters can differ significantly from the parameters that are otherwise used, for example, to generate residual compressive stresses in shot peening or to increase processing efficiency.
• the exact value of the total volume of the hydrogen traps depends on the galvanic coating to be carried out in step b) and therefore varies according to the respective application of the galvanically coated component to be produced.
• the mechanical treatment in Step a) are carried out in such a way that hydrogen traps with a sufficient total volume are generated.
• the volume of the hydrogen penetrating into the mechanically treated surface layer during the electrodeposition in step b), e.g. be determined by experimental preliminary tests and the mechanical treatment in step a) is then carried out such that the total volume of the hydrogen traps generated in the modified sections of the surface layer is greater than or at least equal to this determined volume of hydrogen.
• step b) it is also possible to dispense with an estimate or determination of the amount of hydrogen penetrating into the mechanically treated edge layer during the electrodeposition in step b) if the mechanical treatment in step a) is carried out in such a way that hydrogen traps with a very large, in sufficient total volume is generated in each case.
• the hydrogen generated during the galvanic coating and partially penetrating into the component is essentially completely bound in the edge layer of the component and thus does not lead to hydrogen embrittlement in the regions of the component which are important for the stability of the component can.
• the proportion of diffusible hydrogen that triggers hydrogen embrittlement can thus be minimized.
• the method according to the invention compensates for the ineffectiveness or inadequate effect of inhibitors in some manufacturing steps of the galvanic coating.
• a preferred embodiment of the method according to the invention is characterized in that, prior to step a), it is determined or estimated which volume of hydrogen will penetrate into the mechanically treated edge layer during the electrodeposition in step b), and the mechanical treatment in step a) above it takes place that the total volume of the hydrogen traps generated in the modified sections of the boundary layer is greater than or equal to the volume of hydrogen determined or estimated before step a). In this way it is possible, for example, to achieve that the hydrogen traps generated in the modified sections of the edge layer essentially bind all of the hydrogen penetrating into the mechanically treated edge layer during the electrodeposition in step b).
• a determination of the volume of the hydrogen penetrating into the mechanically treated surface layer during the electrodeposition in step b) can be carried out, for example, by means of thermal desorption spectroscopy (TDS) or by means of hot extraction.
• TDS thermal desorption spectroscopy
• hot extraction by means of a TDS examination of a component into which hydrogen has already penetrated, it is possible to distinguish between the hydrogen which is trapped in hydrogen traps and the hydrogen which is not trapped in hydrogen traps, i.e. free or diffusible.
• the structural modifications in the surface layer can be examined or detected, for example, by means of X-ray diffraction measurements or transmission electron microscopy.
• the mechanical treatment in step a) is carried out by shot peening, deep rolling, rolling, hammering, material-removing processing, preferably grinding, turning, milling, or a combination thereof.
• a further preferred variant of the method according to the invention is characterized in that the component to be coated contains or consists of a crystalline material which is preferably selected from the group consisting of metals, semimetals, ceramics and mixtures thereof.
• the component to be coated preferably contains or consists of a material which is selected from the group consisting of metals, semimetals, ceramics and mixtures thereof.
• the coating (which is electrodeposited in step b) is a coating made of a metal or a metal alloy, the metal and / or the metal alloy preferably being selected from the group consisting of gold, silver, Iron, chromium, nickel, copper, cadmium, palladium, zinc and mixtures and alloys thereof.
• a further preferred variant of the method according to the invention is characterized in that during the mechanical treatment in step a) the structure of the edge layer at least in sections to a depth of more than 0.01 mm, preferably more than 0.1 mm, particularly preferably of more than 0.2 mm, is modified and hydrogen traps are generated in the modified sections of the surface layer.
• Another preferred variant of the method according to the invention is characterized in that, prior to step a), it is determined or estimated to what depth the hydrogen will penetrate into the mechanically treated edge layer during the galvanic deposition in step b), and the mechanical treatment in step a) is carried out in such a way that the hydrogen traps generated in the edge layer are produced, at least in the sections whose surface is to be coated in step b), up to this depth determined or estimated before step a). In this way, it can be prevented, or at least the risk that the hydrogen diffusing into the boundary layer passes the modified area with the hydrogen traps without being trapped in the hydrogen traps.
• the depth is determined before step a) in that the surface of the edge layer of a further component, which consists of the same material as the component to be coated, is provided, at least in sections, with a galvanic coating which consists of the same material as the galvanic coating in step b), and then the depth profile of the hydrogen content in the surface layer is analyzed, this preferably being done by means of secondary ion mass spectrometry (SIMS) and / or glow discharge spectroscopy (GDOES).
• SIMS secondary ion mass spectrometry
• GDOES glow discharge spectroscopy
• a chemical, preferably electrochemical, pretreatment of the surface of the component to be coated is carried out after step a) and before step b).
• the chemical pretreatment of the surface of the component to be coated is preferably selected from the group consisting of degreasing the surface, pickling the surface, pickling the surface, activating the surface and a combination of these pretreatments.
• the present invention also relates to a galvanically coated component, which can be produced or was produced using the method according to the invention.
• This component therefore has structural modifications and hydrogen traps, at least in sections of an edge layer that adjoins the galvanic coating.
• the structural modifications in the edge layer of the component according to the invention can be examined or verified, for example, by means of X-ray diffraction measurements or transmission electron microscopy. This can also be used to estimate the extent of the structural modification. Detection of the hydrogen traps, their binding energies or measurement of the volume of the hydrogen traps is possible using thermal desorption spectroscopy (TDS).
• TDS thermal desorption spectroscopy
• the component according to the invention differs, inter alia, from already known galvanically coated components from the prior art in that the component has more hydrogen traps at least in sections of an (edge) layer adjacent to the galvanic coating and also essentially all of the components present in the galvanically coated component (Atomic and / or molecular) hydrogen is bound in hydrogen traps, which are located in modified sections of an edge layer of the component (adjacent to the galvanic coating). This means that either no or at most only a very small proportion of (atomic and / or molecular) hydrogen is freely available in the component.
• the concentration of the hydrogen which is freely present in the component is preferably at most 2 ppm, particularly preferably at most 1 ppm, very particularly preferably at most 0.5 ppm. Because essentially all of the (atomic and / or molecular) hydrogen present in the component is bound in the hydrogen traps located in the modified sections of the surface layer, this hydrogen cannot penetrate further into the component, but remains in the surface layer . In other words, it can be achieved that there is no (atomic and / or molecular) hydrogen in the central areas that are decisive for the stability of the component.
• the significant reduction in diffusible hydrogen in the component significantly reduces the risk of hydrogen embrittlement. As a result, the component has a lower tendency to brittle failure or a higher tendency Longevity.
• a preferred embodiment of the electroplated component according to the invention is characterized in that the concentration or the proportion of the (atomic and / molecular) hydrogen present in the electroplated component, which is not bound in the hydrogen traps, is a maximum of 2 ppm, preferably a maximum of 1 ppm, particularly preferably a maximum of 0.5 ppm
• a further preferred embodiment of the component according to the invention is characterized in that the component (outside the galvanic coating) contains or consists of a crystalline material which is preferably selected from the group consisting of metals, semimetals, ceramics and mixtures thereof.
• the component preferably contains (outside the galvanic coating) a material which is selected from the group consisting of metals, semimetals, ceramics and mixtures thereof, or consists thereof.
• the coating is a coating made of a metal or a metal alloy, the metal and / or the metal alloy preferably being selected from the group consisting of gold, silver, iron, chromium, nickel, copper, cadmium, Palladium, zinc and mixtures and alloys thereof.
• the present invention also relates to the use of the galvanically coated component according to the invention as a fastening part, for example a screw, as a load-bearing body component, as a roller and / or sliding bearing, as a component of drill rods in oil and gas production, as a component of gas containers or gas lines and / or as a component of aircraft chassis.
• a fastening part for example a screw
• a load-bearing body component as a roller and / or sliding bearing
• drill rods in oil and gas production as a component of gas containers or gas lines and / or as a component of aircraft chassis.
• the first embodiment relates to the avoidance of hydrogen embrittlement of a hardened steel after galvanic coating, by increasing the trap density due to processing.
• the surface condition is characterized by means of X-ray analysis. Usual hard machining parameters are associated with high heat exposure and the development of unfavorable tensile residual stresses, the predominant heat influence does not lead to a significantly increased case density.
• this sample is coated with hard chrome, which leads to the introduction of hydrogen.
• the hydrogen depth profile is determined using GDOES (Glow Discharge Emission Spectroscopy). Due to the small layer thickness and the short coating time, only a near-surface hydrogen input of up to about 0.1 mm can be expected. The proportion of bound hydrogen is also determined by TDS.
• the dislocation density and thus the trap density in the surface layer is increased on a further sample.
• the second embodiment concerns the avoidance of hydrogen embrittlement of a hardened steel after galvanic coating, by increasing the trap density by means of hammers
• the surface condition is characterized by means of X-ray analysis. Without a solidifying surface treatment such as shot peening, hammering or deep rolling, increased dislocation or trap densities are mostly due to the machining finish with a depth of influence ⁇ 0.2 mm. According to the prior art, a sample is coated with a thick hard chrome layer, as is often used for wear protection purposes, which leads to a considerable and deep hydrogen input.
• a deep hydrogen input cannot be determined using GDOES, the analysis depth of GDOES is usually limited to 0.1 mm. Therefore, thin test strips are taken from the edge of the sample, below the coating, and the total hydrogen content is determined by means of hot extraction and the unbound hydrogen content is determined by means of TDS. In this way, hydrogen entry can also be detected to greater depths.
• Another sample is surface-treated by hammering. Increased dislocation densities of up to several millimeters can be achieved and detected using X-ray diffraction.
• the binding of the hydrogen in the surface layer treated according to the invention is checked by means of TDS and hot extraction.

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• 2018
  • 2018-11-09 DE DE102018219181.6A patent/DE102018219181A1/de active Pending
• 2019
  • 2019-10-15 EP EP19203142.5A patent/EP3650586A1/fr active Pending
  • 2019-11-07 US US16/677,536 patent/US11021805B2/en active Active

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