EP0626466A2 - Poussoirs de tasse, procédé de revêtement de poussoirs de tasse et procédé par projection au plasma pour le revêtement de poussoirs de tasse - Google Patents

Poussoirs de tasse, procédé de revêtement de poussoirs de tasse et procédé par projection au plasma pour le revêtement de poussoirs de tasse Download PDF

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Publication number
EP0626466A2
EP0626466A2 EP94107658A EP94107658A EP0626466A2 EP 0626466 A2 EP0626466 A2 EP 0626466A2 EP 94107658 A EP94107658 A EP 94107658A EP 94107658 A EP94107658 A EP 94107658A EP 0626466 A2 EP0626466 A2 EP 0626466A2
Authority
EP
European Patent Office
Prior art keywords
coating
molybdenum
powder
cup
moo3
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP94107658A
Other languages
German (de)
English (en)
Other versions
EP0626466A3 (fr
Inventor
Winfried Heinzel
Thomas Dr. Weber
Peter Goeing
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oerlikon Friction Systems Germany GmbH
Original Assignee
PTG Plasma Oberflaechentechnik GmbH
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 PTG Plasma Oberflaechentechnik GmbH filed Critical PTG Plasma Oberflaechentechnik GmbH
Publication of EP0626466A2 publication Critical patent/EP0626466A2/fr
Publication of EP0626466A3 publication Critical patent/EP0626466A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/14—Tappets; Push rods
    • F01L1/143—Tappets; Push rods for use with overhead camshafts
    • 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
    • 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
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2301/00—Using particular materials

Definitions

  • the invention relates to a method for coating cup tappets consisting essentially of an aluminum alloy.
  • the invention further relates to a cup tappet with a metallic base body, which consists essentially of an aluminum alloy and on the surface of which a coating is arranged.
  • the invention relates to the use of plasma spraying of mixtures of molybdenum and molybdenum trioxide.
  • bucket tappets in internal combustion engines in order to transmit the stroke movement of the cams of the camshaft to the intake and exhaust valves of the internal combustion engine.
  • the cams roll on a support surface of the tappet.
  • a separate base plate made of a particularly resistant material as the support surface or to insert such a base plate into the support surface.
  • Cup tappets have a cylindrical shaft section with which they run axially in a corresponding cylindrical bushing of the cylinder head. This axial surface of the bucket tappet is also subjected to high mechanical loads.
  • the aim is to make the components, even small components such as tappets, as light as possible. In this way, engine noise is reduced and fuel consumption is also reduced because the masses to be moved are smaller.
  • cup tappets entirely or partially from an aluminum alloy.
  • a lightweight bucket tappet is known for example from EP-PS 0 030 780.
  • Aluminum bucket tappets have a lower weight, but due to the lower strength of aluminum, they have the property that the tappets twist during a work cycle, in particular because the actuating force of the cams on the bucket tappet is applied non-uniformly, both in terms of time Course of the operating force as well as the local point of application.
  • a molybdenum plasma wettable powder which contains oxygen and oxides of molybdenum, the oxygen, bound or unbound, being present in a total amount between 0.5 and 15% by weight.
  • the coating powder should, among other things, be can be sprayed onto steel substrates. None is stated about the chemical interaction of the powder with the steel substrate.
  • DE-PS 38 14 362 describes a process for the production of tappets. After that, the bucket tappets are to be provided with wear-resistant, corrosion and thermal shock-resistant layers made of a carbide or oxide-ceramic-silicide material in a plasma spraying process. This requires post-processing of the applied layer using a hot isostatic pressing process at over 1000 ° C.
  • the invention is therefore based on the object of specifying a cup tappet and a method for its production, with which the abrasion resistance of cup tappets, in particular in the region of the cylindrical shaft section, can be improved.
  • this object is achieved according to the invention in that, in the plasma spraying process, a powder mixture is applied as a coating to a surface of the tappet, which contains molybdenum and molybdenum trioxide, the oxygen content of the mixture being between 2% and 8%.
  • the powder mixture is plasma-sprayed with the supply of oxygen, and the molybdenum trioxide is generated by partial oxidation of the molybdenum powder during the plasma spraying.
  • This measure has the advantage that only one type of molybdenum powder has to be kept ready for the mixture and that the oxygen content can be adjusted sensitively by appropriately metering the oxygen supply. It is particularly preferred if the oxygen is used as the conveying gas for the molybdenum powder.
  • This measure has the advantage that the oxygen supply also has a transport function for the powder.
  • the powder mixture is plasma-sprayed without oxygen, the powder mixture containing molybdenum powder and molybdenum trioxide powder.
  • This measure has the advantage that the oxygen content can be fixed by appropriate preparation of the powder mixture and no disturbances in an oxygen supply can have an effect.
  • the powder mixture contains at least 5% molybdenum (Mo) + molybdenum trioxide (MoO3) and, moreover, a filler.
  • Mo molybdenum
  • MoO3 molybdenum trioxide
  • the powder mixture contains 30% to 70% of a filler, with metallic powders, in particular steel powders and ceramic powders, in particular aluminum oxide powders, being preferred as fillers.
  • This measure has the advantage that a significant reduction in costs can be achieved without loss of surface properties, because the fillers mentioned only cause about 1/10 of the costs of molybdenum.
  • the powder mixture has a grain size of 5 ⁇ m to 45 ⁇ m.
  • the oxygen content is 2.5% to 3.5%, preferably 3%.
  • the coating has a thickness of 30 ⁇ m to 250 ⁇ m, preferably 80 ⁇ m to 150 ⁇ m, more preferably 100 ⁇ m to 120 ⁇ m.
  • the method according to the invention can in principle be used on all loaded surfaces of the cup tappet, it is preferably used on the surface of a cylindrical wall of a shaft section of the cup tappet.
  • the aluminum alloy consists of extruded aluminum with approximately 7% zinc and less than 1% magnesium and copper in each case.
  • a particularly good effect is achieved in that the surface is kept at a temperature of at most 180 ° C. during the plasma spraying by cooling.
  • This measure has the advantage that the material properties of the aluminum alloy are not impaired by excessively high temperatures.
  • the coating is ground after it has been applied.
  • This measure has the advantage that there is a particularly good surface structure and it has been shown that the coating applied according to the invention can also be smoothed over without problems.
  • Fig. 1 10 generally designates a conventional cylinder head of an internal combustion engine.
  • a camshaft 11 is provided with cams 12.
  • the cam 12 shown actuates against the force of a spring 13 a valve 14 of the internal combustion engine, which can be an intake or an exhaust valve.
  • the valve 14 is provided at its lower end with a valve plate 15 which, for example, can connect an intake line 16 to a combustion chamber 17 or shut it off. 18 with a cylinder is indicated, which is positioned below the combustion chamber 17.
  • a bucket tappet 20 is provided in order to convert the rotary movement of the cam 12 into the required axial movement of the valve 14.
  • the cup tappet 20 has a radial support surface 21 on its side facing the cam 12.
  • a base plate 22 can be inserted or placed in the support surface 21.
  • a cylindrical shaft section 23 of the cup tappet 20 runs in an associated bushing of the cylinder head.
  • the shaft section 23 essentially consists of a hollow cylindrical wall 24 on which a coating 25 is applied.
  • the coating 25 thus serves to improve the sliding properties and thus to increase the service life of the cup tappet 20 in the region of its shaft section 23.
  • the base body of the cup tappet 20 and thus also the wall 24 of the shaft section 23 consists of an aluminum alloy, preferably AlZn7MgCu.
  • This special aluminum alloy thus differs from aluminum alloys (AlSi), as they are used for conventional tappets.
  • AlSi aluminum alloys
  • the aluminum alloy used in the context of the present invention essentially consists of extruded aluminum with approximately 7% zinc (Zn) and less than 1% magnesium (Mg) and copper (Cu). However, this aluminum alloy is sensitive to temperature because its material properties are impaired at temperatures above 180 ° C.
  • Mo molybdenum
  • MoO3 molybdenum trioxide
  • the known plasma spraying method is used to apply the coating 25.
  • a pure molybdenum powder is used for plasma spraying, in which the desired oxide content is generated by so-called reactive spraying during the spraying process.
  • oxygen is used as the conveying gas for the molybdenum powder, so that the molybdenum powder is in an atmosphere consisting at least partially of oxygen when it passes through the plasma.
  • the molybdenum powder is therefore partially oxidized by suitable adjustment of the process parameters, so that both pure molybdenum and molybdenum trioxide strike the surface 26 of the wall 24.
  • an inert conveying gas is used for the coating powder in the usual way.
  • a corresponding agglomerated powder mixture of Mo powder and MoO3 powder is fed to the plasma spraying device.
  • the oxygen content is always between 2% and 8%, preferably between 2.5% and 3.5%, in particular 3%.
  • the powders used have a grain size that is preferably between 5 ⁇ m and 45 ⁇ m.
  • the aluminum alloy (AlZn7MgCu) which is preferably used is sensitive to temperature, so that the workpieces (the cup tappets 20) are cooled in the process according to the invention in such a way that the surface to be coated does not become warmer than 180.degree.
  • a filler in a further variant of the invention, which consists of a less expensive material.
  • Particularly suitable fillers are metallic powders, for example steel powders and / or ceramic powders, in particular aluminum oxide powders (Al2O3).
  • FIG 3 illustrates how the coating 25 is applied to the surface 26 of the wall 24.
  • Mo particles 30 and MoO3 particles 31 fly at high speed to the surface 26 of the wall 24.
  • the spray jet has a temperature of over 3000 ° C. and the particles 30, 31 fly towards the surface 26 at high speed, in some coating processes even at supersonic speed.
  • the MoO3 particles 31 can be attached to the Mo particles 30, especially when the MoO3 fractions have only been generated by oxidation in the plasma jet by reactive spraying.
  • the diffusion mechanism described above takes place on a microscopic scale.
  • the thickness of the diffusion zone 35 according to FIG. 4 is typically less than 1 ⁇ m.
  • the diffusion zone 35 enormously increases the adhesive strength of the coating 25 on the wall 24.
  • the binary phase diagram Al — Mo shown in FIG. 5 shows on the Mo-rich side an astonishingly high solubility of the aluminum in molybdenum at higher temperatures.
  • the molybdenum can absorb up to 20% aluminum in solution there. This is in contrast to other material combinations, for example Mo - Cu or Mo - Zn.
  • Their binary phase diagrams show a complete insolubility of the elements involved with each other in the solid and in the liquid state. In the context of the present method, therefore, this exceptional property in the Al-Mo phase diagram is used by using this property specifically to improve the adhesive strength of the coating.
  • FIG. 6 shows a micrograph through an example of a coating as it was produced in the context of the present invention. It can be seen that the coating 25 was applied with a thickness of approximately 200 ⁇ m. The area of the coating 25 consisting of molybdenum is indicated uniformly by 50 in FIG. 6.
  • the areas made of molybdenum trioxide are designated by 51. These areas 51 are formed as flat cakes, which is explained by the fact that the MoO3 particles also hit in a pasty state and therefore deform in the form of a cake to subsequently solidify in this form.
  • pores are designated, as they typically occur with coatings in the plasma spray process.
  • the degree of porosity can be set within wide limits.
  • a fine-grained structure was produced with a coating according to FIG. 6.
  • the layer strength ⁇ H was measured with more than 50 MPa.
  • the phase distribution between Mo and MoO3 proved to be homogeneous.
  • the layer hardness was 550 HV 0.3, while the layer remained ductile.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Coating By Spraying Or Casting (AREA)
EP94107658A 1993-05-25 1994-05-18 Poussoirs de tasse, procédé de revêtement de poussoirs de tasse et procédé par projection au plasma pour le revêtement de poussoirs de tasse. Withdrawn EP0626466A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4317350A DE4317350C2 (de) 1993-05-25 1993-05-25 Verfahren zum Beschichten von Tassenstösseln
DE4317350 1993-05-25

Publications (2)

Publication Number Publication Date
EP0626466A2 true EP0626466A2 (fr) 1994-11-30
EP0626466A3 EP0626466A3 (fr) 1995-12-20

Family

ID=6488853

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94107658A Withdrawn EP0626466A3 (fr) 1993-05-25 1994-05-18 Poussoirs de tasse, procédé de revêtement de poussoirs de tasse et procédé par projection au plasma pour le revêtement de poussoirs de tasse.

Country Status (2)

Country Link
EP (1) EP0626466A3 (fr)
DE (1) DE4317350C2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997013884A1 (fr) * 1995-10-06 1997-04-17 Ford Motor Company Limited Procede pour deposer des revetements metalliques composites
EP0922786A2 (fr) 1997-11-25 1999-06-16 Fuji Kihan Co., Ltd. Produit revêtu de céramique et procédé de sa fabrication

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19822903C2 (de) * 1998-05-22 2001-11-22 Daimler Chrysler Ag Verfahren zur Herstellung einer Beschichtungen eines Tassenstößels sowie Tassenstößel
DE19837945A1 (de) * 1998-08-21 2000-02-24 Asea Brown Boveri Schaltanordnung und Verfahren zu ihrer Herstellung
DE19945318C2 (de) * 1999-09-22 2001-12-13 Hartmetall Beteiligungs Gmbh Verfahren zur Herstellung sphäroidisierter Hartstoffpulver

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2234382A1 (en) * 1973-06-22 1975-01-17 Metallisation Ste Nouvelle Partially oxidised molybdenum coatings - deposited using plasma torch to give a surface of increased coefft of friction
US4146388A (en) * 1977-12-08 1979-03-27 Gte Sylvania Incorporated Molybdenum plasma spray powder, process for producing said powder, and coatings made therefrom
DE3802920C1 (fr) * 1988-02-02 1989-05-03 Goetze Ag, 5093 Burscheid, De
DE3814362C1 (en) * 1988-04-28 1989-12-07 Thyssen Guss Ag, 4330 Muelheim, De Process for producing bucket tappets and similarly stressed components in internal combustion engines

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997013884A1 (fr) * 1995-10-06 1997-04-17 Ford Motor Company Limited Procede pour deposer des revetements metalliques composites
EP0922786A2 (fr) 1997-11-25 1999-06-16 Fuji Kihan Co., Ltd. Produit revêtu de céramique et procédé de sa fabrication
EP0922786A3 (fr) * 1997-11-25 2001-04-25 Fuji Kihan Co., Ltd. Produit revêtu de céramique et procédé de sa fabrication

Also Published As

Publication number Publication date
EP0626466A3 (fr) 1995-12-20
DE4317350A1 (de) 1994-12-01
DE4317350C2 (de) 1995-04-20

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