WO2006010450A1 - Piston rod comprising a covering layer consisting of a cobalt alloy - Google Patents

Piston rod comprising a covering layer consisting of a cobalt alloy Download PDF

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Publication number
WO2006010450A1
WO2006010450A1 PCT/EP2005/007401 EP2005007401W WO2006010450A1 WO 2006010450 A1 WO2006010450 A1 WO 2006010450A1 EP 2005007401 W EP2005007401 W EP 2005007401W WO 2006010450 A1 WO2006010450 A1 WO 2006010450A1
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WO
WIPO (PCT)
Prior art keywords
piston rod
weight percent
cover layer
microns
rod according
Prior art date
Application number
PCT/EP2005/007401
Other languages
German (de)
French (fr)
Inventor
Marius Van Der Heijden
Original Assignee
Bosch Rexroth Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bosch Rexroth Ag filed Critical Bosch Rexroth Ag
Priority to DE112005001756T priority Critical patent/DE112005001756A5/en
Publication of WO2006010450A1 publication Critical patent/WO2006010450A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/144—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor the fluid stream containing particles, e.g. powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/32—Bonding taking account of the properties of the material involved
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/34—Laser welding for purposes other than joining
    • B23K26/342—Build-up welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
    • B23K35/0244—Powders, particles or spheres; Preforms made therefrom
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • B23K35/3046—Co as the principal constituent
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C23C4/08—Metallic material containing only metal elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/003—Pistons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/34—Coated articles, e.g. plated or painted; Surface treated articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/18—Dissimilar materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/18—Dissimilar materials
    • B23K2103/26—Alloys of Nickel and Cobalt and Chromium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26

Definitions

  • the invention relates to a piston rod according to the preamble of patent claim 1.
  • Hydraulic cylinder piston rods which are used near water or in the water in industry, off-shore, bridges, and locks, are exposed to aggressive environmental conditions requiring special piston rod corrosion protection, usually made of ordinary carbon steel do.
  • piston rods are provided with a metallic layer of chromium or a nickel-chromium alloy.
  • a metallic layer is chemically susceptible in an aggressive environment. It occurs corrosion and in particular so-called pitting, which makes the piston rod unusable after some time.
  • Titanium oxide has the disadvantage that it is a semiconductor and tends to pitting together with the metallic adhesive layer.
  • alumina alone is brittle and tends to crack under stress.
  • Another disadvantage is that the mixture has a relatively high coefficient of friction and thus the piston rod seals are heavily loaded.
  • the object of the present invention is to provide a piston rod for a hydraulic cylinder, which has a cover layer with high corrosion resistance and a low coefficient of friction.
  • a cover layer of a cobalt-based alloy is applied to the piston rod of a hydraulic cylinder.
  • This alloy has a high corrosion resistance, so that the pitting is suppressed. Furthermore, it has a low coefficient of friction, which not only improves the response of the piston rod, but also the wear on the
  • Piston rod seals is reduced. Furthermore, the application of an adhesive layer to the piston rod is not required, so that the production of the piston rod coated according to the invention is simplified.
  • a particularly good topcoat can be achieved when the alloy contains about 26 weight percent chromium, 9 weight percent nickel, 5 weight percent molybdenum, 2 weight percent tungsten, 0.06 weight percent carbon, 0.5 weight percent silicon, and about 3 weight percent iron besides cobalt.
  • the application of the cover layer can be carried out by laser deposition welding or plasma spraying.
  • the alloy is in powder form and preferably has a particle size between 40 microns and 200 microns. Depending on the grade of the alloy, the particle size preferably moves between 45 microns and 150 microns or 53 microns _ and 180 microns.
  • the cover layer is applied in a layer thickness of about 150 microns to about 1000 microns.
  • a profile for a displacement measuring system can be integrated, so that the respective piston stroke can be detected.
  • the cover layer is ground off in such a way that a smooth surface is formed on the outer surface of which the profile is not shown.
  • FIGURE shows a longitudinal section through a portion of a piston rod according to the invention.
  • the piston rod 2 according to the invention of a hydraulic cylinder has a base body 4, in which a plurality of transversely extending to the longitudinal direction, evenly spaced transverse grooves 6 are introduced. During a stroke of the piston rod 2, a magnetic field is generated by the transverse grooves 6, the changes of which can be detected by a displacement transducer 8.
  • the main body 4 is preferably made of ordinary carbon steel.
  • a cover layer 10 is applied, which consists of a cobalt-based alloy.
  • the alloy contains about 26 weight percent chromium, 9 weight percent nickel, 5 weight percent molybdenum, 2 weight percent tungsten, 0.06 weight percent carbon, 0.5 weight percent silicon, and about 3 weight percent iron.
  • the alloy is in powder form and has a particle size between 40 microns and 200 microns. Depending on the grade of the alloy, the particle size is preferably 45 microns to 150 microns or 53 microns to 180 microns.
  • the cover layer 10 is applied by laser deposition welding or by plasma spraying with a layer thickness of about 150 micrometers up to 1000 micrometers.
  • the laser deposition welding is characterized by a low thermal load on the piston rod 2 and a high dimensional stability.
  • the inventive alloy is particularly good weldability due to their good elongation.
  • a laser beam is preferably directed perpendicularly to the base body 4 and focused in such a way that a local melt pool is formed on the base body 4.
  • a protective gas stream is directed, which blows the alloy in powder form at the same time in the molten bath. Due to the high thermal conductivity of the base body 4 and the rapid relative movement between the base body 4 and the laser beam, the molten bath is cooled immediately after the injection of the powder.
  • the cover layer 10 is a very homogeneous and pore-free cover layer 10 with little mixing of the base material, ie the respective surface portion of the base body 4, so that the laser deposition welding, inter alia, is particularly suitable for piston rods 2 with integrated profiles for WegmessSysteme.
  • the transverse grooves 6 are also visible in the surface 12 thereof. Since the cover layer 10 is relatively uneven, it is ground down until a completely flat, smooth surface forms over the base body 4, in which the transverse grooves 6 do not are more visible. Accordingly, the depth of the ablation is greater than the depth of the transverse grooves. 6
  • an arc burning in a nozzle heats an inert gas stream of, for example, argon, nitrogen or helium to about 15,000 degrees Celsius, which leads to cleavage of the molecular gas and partial ionization of the atoms.
  • the plasma flows out of the nozzle at high speed.
  • the flow velocity of the plasma jet can be close to the speed of sound.
  • the alloy is injected to form the cover layer 10 in powder form by means of a carrier gas.
  • the particles are in the plasma stream for about 0.5 ms. They are melted and fired on the adhesive layer 10.
  • the particles Upon impact with the base body 4, the particles are flattened and cooled by the heat transfer into the base 4 from instantaneously, so that they solidify and shrink.
  • the resulting cover layer 10 adheres predominantly by mechanical clamping to the base body 4th
  • the plasma spraying process (PTA or plasma impregnated are) due to the increased thermal load the risk that the transverse grooves 6 and thus the profile of the WegmessSystems melts. To prevent this danger, the plasma spraying process mainly applied to piston rods without integrated transverse grooves 6.
  • Hydraulic cylinder with a metallic base body, on which a cover layer of a cobalt-based alloy is applied.

Abstract

The invention relates to a piston rod for a hydraulic cylinder, comprising a metallic base body to which a covering layer consisting of a cobalt-based alloy is applied.

Description

KOLBENSTANGE MIT DECKSCHICHT AUS KOBALT-LEGIERUNG PISTON ROD WITH COBALT ALLOY COVERING
Die Erfindung betrifft eine Kolbenstange nach dem Oberbegriff des Patentanspruchs 1.The invention relates to a piston rod according to the preamble of patent claim 1.
Kolbenstangen von Hydraulikzylindern, die in der Industrie, dem Off-Shore-Bereich, an Brücken und Schleusen wassernah oder im Wasser eingesetzt werden, sind aggressiven Umgebungseinflüssen ausgesetzt, die einen besonderen Korrosionsschutz für die Kolbenstange, die üblicherweise aus einem normalen Kohlenstoffstahl hergestellt ist, notwendig machen.Hydraulic cylinder piston rods, which are used near water or in the water in industry, off-shore, bridges, and locks, are exposed to aggressive environmental conditions requiring special piston rod corrosion protection, usually made of ordinary carbon steel do.
Üblicherweise sind Kolbenstangen mit einer metallischen Schicht aus Chrom oder einer Nickel- Chromlegierung versehen. Eine solche Schicht ist in einer aggressiven Umgebung chemisch anfällig. Es tritt Korrosion und insbesondere sogenannter Lochfraß auf, der die Kolbenstange nach einiger Zeit unbrauchbar macht.Usually, piston rods are provided with a metallic layer of chromium or a nickel-chromium alloy. Such a layer is chemically susceptible in an aggressive environment. It occurs corrosion and in particular so-called pitting, which makes the piston rod unusable after some time.
Aus der DE 39 10 725 Cl ist es bekannt, eine Kolbenstange mit einer metallischen HaftSchicht zu versehen und auf diese eine keramische Deckschicht aus einer Mischung aus Aluminiumoxid und Titanoxid aufzutragen.From DE 39 10 725 Cl it is known to provide a piston rod with a metallic adhesive layer and apply to this a ceramic cover layer of a mixture of alumina and titanium oxide.
Titanoxid hat den Nachteil, dass es ein Halbleiter ist und zusammen mit der metallischen Haftschicht zur Lochfraßbildung neigt. Alumiumoxid alleine ist jedoch spröde und neigt bei Beanspruchung zur Rissbildung. Weiterhin ist nachteilig, dass die Mischung einen relativ hohen Reibwert hat und somit die Kolbenstangendichtungen stark belastet werden. Aufgabe der vorliegenden Erfindung ist es, eine Kolbenstange für einen Hydraulikzylinder zu schaffen, die eine Deckschicht mit hoher Korrosionsbeständigkeit und einem geringen Reibwert aufweist.Titanium oxide has the disadvantage that it is a semiconductor and tends to pitting together with the metallic adhesive layer. However, alumina alone is brittle and tends to crack under stress. Another disadvantage is that the mixture has a relatively high coefficient of friction and thus the piston rod seals are heavily loaded. The object of the present invention is to provide a piston rod for a hydraulic cylinder, which has a cover layer with high corrosion resistance and a low coefficient of friction.
Diese Aufgabe wird durch eine Kolbenstange mit den Merkmalen nach dem Patentanspruch 1 gelöst.This object is achieved by a piston rod having the features of claim 1.
Ξrfindungsgemäß ist auf die Kolbenstange eines Hydraulikzylinders eine Deckschicht aus einer Legierung auf Kobalt-Basis aufgetragen.According to the invention, a cover layer of a cobalt-based alloy is applied to the piston rod of a hydraulic cylinder.
Diese Legierung hat eine hohe Korrossionsfestigkeit, so dass die Lochfraßbildung unterdrückt wird. Weiterhin weist sie einen geringen Reibwert auf, wodurch nicht nur das Ansprechverhalten der Kolbenstange verbessert, sondern auch der Verschleiß an denThis alloy has a high corrosion resistance, so that the pitting is suppressed. Furthermore, it has a low coefficient of friction, which not only improves the response of the piston rod, but also the wear on the
Kolbenstangendichtungen reduziert ist. Ferner ist der Auftrag einer Haftschicht auf die Kolbenstange nicht erforderlich, so dass die Herstellung der erfindungsgemäß beschichteten Kolbenstange vereinfacht ist.Piston rod seals is reduced. Furthermore, the application of an adhesive layer to the piston rod is not required, so that the production of the piston rod coated according to the invention is simplified.
Eine besonders gute Deckschicht lässt sich erzielen, wenn die Legierung neben Kobalt etwa 26 Gewichtsprozent Chrom, 9 Gewichtsprozent Nickel, 5 Gewichtsprozent Molybdän, 2 Gewichtsprozent Wolfram, 0,06 Gewichtsprozent Kohlenstoff, 0,5 Gewichtsprozent Silizium und etwa 3 Gewichtsprozent Eisen enthält.A particularly good topcoat can be achieved when the alloy contains about 26 weight percent chromium, 9 weight percent nickel, 5 weight percent molybdenum, 2 weight percent tungsten, 0.06 weight percent carbon, 0.5 weight percent silicon, and about 3 weight percent iron besides cobalt.
Das Auftragen der Deckschicht kann durch Laserauftragsschweißen oder Plasmaspritzen erfolgen. Dabei liegt die Legierung in Pulverform vor und hat vorzugsweise eine Teilchengröße zwischen 40 Mikrometern und 200 Mikrometern. Je nach Gütegrad der Legierung bewegt sich die Teilchengröße bevorzugterweise zwischen 45 Mikrometer und 150 Mikrometer bzw. 53 Mikrometer _und 180 Mikrometer.The application of the cover layer can be carried out by laser deposition welding or plasma spraying. The alloy is in powder form and preferably has a particle size between 40 microns and 200 microns. Depending on the grade of the alloy, the particle size preferably moves between 45 microns and 150 microns or 53 microns _ and 180 microns.
Vorteilhafterweise ist die Deckschicht in einer Schichtdicke von etwa 150 Mikrometern bis zu etwa 1000 Mikrometern aufgetragen.Advantageously, the cover layer is applied in a layer thickness of about 150 microns to about 1000 microns.
In der Kolbenstange kann ein Profil für ein Wegmesssystem integriert sein, so dass der jeweilige Kolbenhub erfassbar ist. Vorzugsweise ist die Deckschicht nach dem Auftrag derart abgeschliffen, dass sich eine glatte Oberfläche bildet, an deren Aussenflache das Profil nicht abgebildet ist.In the piston rod, a profile for a displacement measuring system can be integrated, so that the respective piston stroke can be detected. Preferably, after the application, the cover layer is ground off in such a way that a smooth surface is formed on the outer surface of which the profile is not shown.
Sonstige vorteilhafte Ausführungsformen sind Gegenstand weiterer Unteransprüche.Other advantageous embodiments are the subject of further subclaims.
Im Folgenden wird eine bevorzugte Ausführungsform der Erfindung anhand einer schematischen Darstellung näher erläutert. Die einzige Figur zeigt einen Längsschnitt durch einen Abschnitt einer erfindungsgemäßen Kolbenstange.In the following, a preferred embodiment of the invention is explained in more detail with reference to a schematic representation. The single FIGURE shows a longitudinal section through a portion of a piston rod according to the invention.
Die erfindungsgemäße Kolbenstange 2 eines Hydraulikzylinders hat einen Grundkörper 4, in dem eine Vielzahl von quer zur Längsrichtung verlaufende, gleichmäßig voneinander beabstandete Querrillen 6 eingebracht sind. Bei einem Hub der Kolbenstange 2 wird durch die Querrillen 6 ein Magnetfeld generiert, dessen Änderungen durch einen Wegaufnehmer 8 erfassbar sind.The piston rod 2 according to the invention of a hydraulic cylinder has a base body 4, in which a plurality of transversely extending to the longitudinal direction, evenly spaced transverse grooves 6 are introduced. During a stroke of the piston rod 2, a magnetic field is generated by the transverse grooves 6, the changes of which can be detected by a displacement transducer 8.
Der Grundkörper 4 ist vorzugsweise aus einem gewöhnlichen Kohlenstoffstahl hergestellt. Auf den Grundkörper 4 ist eine Deckschicht 10 aufgebracht, die aus einer Legierung auf Kobalt-Basis besteht. Neben Kobalt enthält die Legierung etwa 26 Gewichtsprozent Chrom, 9 Gewichtsprozent Nickel, 5 Gewichtsprozent Molybdän, 2 Gewichtsprozent Wolfram, 0,06 Gewichtsprozent Kohlenstoff, 0,5 Gewichtsprozent Silizium und etwa 3 Gewichtsprozent Eisen. Im nicht aufgetragenen Zustand liegt die Legierung in Pulverform vor und hat eine Teilchengröße zwischen 40 Mikrometern und 200 Mikrometern. Je nach Gütegrad der Legierung beträgt die Teilchengröße bevorzugterweise 45 Mikrometer bis 150 Mikrometer bzw. 53 Mikrometer bis 180 Mikrometer.The main body 4 is preferably made of ordinary carbon steel. On the base body 4, a cover layer 10 is applied, which consists of a cobalt-based alloy. In addition to cobalt, the alloy contains about 26 weight percent chromium, 9 weight percent nickel, 5 weight percent molybdenum, 2 weight percent tungsten, 0.06 weight percent carbon, 0.5 weight percent silicon, and about 3 weight percent iron. When not applied, the alloy is in powder form and has a particle size between 40 microns and 200 microns. Depending on the grade of the alloy, the particle size is preferably 45 microns to 150 microns or 53 microns to 180 microns.
Die Deckschicht 10 ist via Laserauftragsschweißen oder im Plasmaspritzverfahren mit einer Schichtdicke von etwa 150 Mikrometern bis zu 1000 Mikrometern aufgetragen.The cover layer 10 is applied by laser deposition welding or by plasma spraying with a layer thickness of about 150 micrometers up to 1000 micrometers.
Das Laserauftragsschweißen zeichnet sich durch eine geringe thermische Belastung der Kolbenstange 2 und eine hohe Maßhaltigkeit aus. Dabei ist die erfindungsgemässe Legierung aufgrund ihrer guten Dehnung besonders gut schweißbar. Beim Laserauftragsschweißen wird ein Laserstrahl vorzugsweise senkrecht auf den Grundkörper 4 gerichtet und derart fokussiert, dass sich ein lokales Schmelzbad auf den Grundkörper 4 ausbildet. Auf das Schmelzbad wird ein Schutzgasstrom gerichtet, der zugleich die Legierung in Pulverform in das Schmelzbad bläst. Aufgrund der hohen Wärmeleitfähigkeit des Grundkörpers 4 und der schnellen Relativbewegung zwischen dem Grundkörper 4 und dem Laserstrahl kühlt sich das Schmelzbad sofort nach dem Einblasen des Pulvers ab. Es entsteht eine sehr homogene und porenfreie Deckschicht 10 mit wenig Aufmischung des Basismaterials d.h. des jeweiligen Oberflächenabschnitts des Grundkörpers 4, so dass das Laserauftragsschweißen unter anderem besonders geeignet ist für Kolbenstangen 2 mit integrierten Profilen für WegmessSysteme. Nach dem Aufbringen der Deckschicht 10 zeigen sich auch in deren Oberfläche 12 die Querrillen 6. Da die Deckschicht 10 verhältnismäßig uneben ist, wird sie soweit abgeschliffen, bis sich über dem Grundkörper 4 eine völlig ebene, glatte Oberfläche ausbildet, in der die Querrillen 6 nicht mehr sichtbar sind. Entsprechend ist die Tiefe der Abtragung größer als die Tiefe der Querrillen 6.The laser deposition welding is characterized by a low thermal load on the piston rod 2 and a high dimensional stability. In this case, the inventive alloy is particularly good weldability due to their good elongation. In laser deposition welding, a laser beam is preferably directed perpendicularly to the base body 4 and focused in such a way that a local melt pool is formed on the base body 4. On the molten bath, a protective gas stream is directed, which blows the alloy in powder form at the same time in the molten bath. Due to the high thermal conductivity of the base body 4 and the rapid relative movement between the base body 4 and the laser beam, the molten bath is cooled immediately after the injection of the powder. The result is a very homogeneous and pore-free cover layer 10 with little mixing of the base material, ie the respective surface portion of the base body 4, so that the laser deposition welding, inter alia, is particularly suitable for piston rods 2 with integrated profiles for WegmessSysteme. After the application of the cover layer 10, the transverse grooves 6 are also visible in the surface 12 thereof. Since the cover layer 10 is relatively uneven, it is ground down until a completely flat, smooth surface forms over the base body 4, in which the transverse grooves 6 do not are more visible. Accordingly, the depth of the ablation is greater than the depth of the transverse grooves. 6
Beim Plasmaspritzverfahren erhitzt ein in einer Düse brennender Lichtbogen einen inerten Gasström aus bspw. Argon, Stickstoff oder Helium auf circa 15000 Grad Celsius, was zur Spaltung des molekularen Gases und zur teilweisen Ionisation der Atome führt. Als Folge der hohen Temperatur strömt das Plasma mit hoher Geschwindigkeit aus der Düse aus. In bekannten Plasmaspritzanlagen kann die Strömungsgeschwindigkeit des Plasmastrahls nahe der Schallgeschwindigkeit liegen. In diesen hochenergetischen Plasmastrahl wird die Legierung zur Bildung der Deckschicht 10 in Pulverform mit Hilfe eines Trägergases injiziert. Dabei befinden sich die Teilchen etwa 0,5 ms im Plasmastrom. Sie werden aufgeschmolzen und auf die HaftSchicht 10 geschossen. Beim Aufprall auf den Grundkörper 4 werden die Teilchen abgeplattet und kühlen durch den Wärmeübertrag in den Grundkörper 4 augenblicklich ab, so dass sie erstarren und schrumpfen. Die so entstehende Deckschicht 10 haftet vorwiegend durch mechanische Verklammerung an dem Grundkörper 4.In the plasma spraying process, an arc burning in a nozzle heats an inert gas stream of, for example, argon, nitrogen or helium to about 15,000 degrees Celsius, which leads to cleavage of the molecular gas and partial ionization of the atoms. As a consequence of the high temperature, the plasma flows out of the nozzle at high speed. In known plasma spray systems, the flow velocity of the plasma jet can be close to the speed of sound. In this high-energy plasma jet, the alloy is injected to form the cover layer 10 in powder form by means of a carrier gas. The particles are in the plasma stream for about 0.5 ms. They are melted and fired on the adhesive layer 10. Upon impact with the base body 4, the particles are flattened and cooled by the heat transfer into the base 4 from instantaneously, so that they solidify and shrink. The resulting cover layer 10 adheres predominantly by mechanical clamping to the base body 4th
Beim Plasmaspritzverfahren (PTA bzw. Plasma Tränsferred Are) ist aufgrund der erhöhten thermischen Belastung die Gefahr gegeben, dass die Querrillen 6 und somit das Profil des WegmessSystems abschmilzt. Um dieser Gefahr vorzubeugen, wird das Plasmaspritzverfahren vorwiegend bei Kolbenstangen ohne integrierte Querrillen 6 angewendet.In the plasma spraying process (PTA or plasma impregnated are) due to the increased thermal load the risk that the transverse grooves 6 and thus the profile of the WegmessSystems melts. To prevent this danger, the plasma spraying process mainly applied to piston rods without integrated transverse grooves 6.
Offenbart ist eine Kolbenstange für einenDisclosed is a piston rod for a
Hydraulikzylinder mit einem metallischen Grundkörper, auf dem eine Deckschicht aus einer Legierung auf Kobalt-Basis aufgetragen ist. Hydraulic cylinder with a metallic base body, on which a cover layer of a cobalt-based alloy is applied.
BezugszeichenlisteLIST OF REFERENCE NUMBERS
Kolbenstange Grundkörper Querrille Wegaufnehmer Deckschicht Oberfläche nach Laserauftragsschweißen Piston rod Main body Transverse groove Transducer Surface layer Surface after laser deposition welding

Claims

Ansprüche claims
1. Kolbenstange für einen Hydraulikzylinder aus einem metallischen Grundkörper (4) , auf dem eine Deckschicht (10) aufgetragen ist, dadurch gekennzeichnet, dass die Deckschicht (10) aus einer Legierung auf Kobalt-Basis besteht.1. piston rod for a hydraulic cylinder of a metallic base body (4) on which a cover layer (10) is applied, characterized in that the cover layer (10) consists of a cobalt-based alloy.
2. Kolbenstange nach Anspruch 1, wobei die Legierung neben Kobalt etwa 26 Gewichtsprozent Chrom, 9 Gewichtsprozent Nickel, 5 Gewichtsprozent Molybdän, 2 Gewichtsprozent Wolfram, 0,06 Gewichtsprozent Kohlenstoff, 0,5 Gewichtsprozent Silizium und etwa 3 Gewichtsprozent Eisen enthält.A piston rod according to claim 1, wherein the alloy contains about 26 weight percent chromium, 9 weight percent nickel, 5 weight percent molybdenum, 2 weight percent tungsten, 0.06 weight percent carbon, 0.5 weight percent silicon and about 3 weight percent iron in addition to cobalt.
3. Kolbenstange nach Anspruch 1 oder 2, wobei die Legierung eine Teilchengröße zwischen 40 Mikrometer und 200 Mikrometer aufweist.3. Piston rod according to claim 1 or 2, wherein the alloy has a particle size between 40 microns and 200 microns.
4. Kolbenstange nach Anspruch 1, 2 oder 3, wobei die Dicke der Deckschicht (10) zwischen 150 Mikrometer und 1000 Mikrometer beträgt.4. Piston rod according to claim 1, 2 or 3, wherein the thickness of the cover layer (10) is between 150 microns and 1000 microns.
5. Kolbenstange nach einem der vorhergehenden Ansprüche, wobei der Grundkörper (4) ein Profil (6) für ein Wegmesssystem (8) aufweist.5. Piston rod according to one of the preceding claims, wherein the base body (4) has a profile (6) for a displacement measuring system (8).
6. Kolbenstange nach Anspruch 5, wobei die Deckschicht (10) eine abgeschliffene Oberfläche hat, in der das Profil (6) nicht abgebildet ist.6. Piston rod according to claim 5, wherein the cover layer (10) has a sanded surface in which the profile (6) is not shown.
7. Kolbenstange nach einem der vorhergehenden Ansprüche, wobei die Deckschicht (10) durch7. Piston rod according to one of the preceding claims, wherein the cover layer (10) by
Laserauftragsschweißen aufgebracht ist. Kolbenstange nach einem der Ansprüche 1 bis 4, wobei die Deckschicht (10) durch ein Plasmaspritzverfahren aufgebracht ist. Laser deposition welding is applied. Piston rod according to one of claims 1 to 4, wherein the cover layer (10) is applied by a plasma spraying process.
PCT/EP2005/007401 2004-07-26 2005-07-08 Piston rod comprising a covering layer consisting of a cobalt alloy WO2006010450A1 (en)

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