Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
  • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
  • F02M61/166—Selection of particular materials
• • 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
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/02—Pretreatment of the material to be coated
  • C23C14/024—Deposition of sublayers, e.g. to promote adhesion of the coating
  • C23C14/025—Metallic sublayers
• • 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
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/32—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer
  • C23C28/322—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one pure metallic layer only coatings of metal elements only
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/343—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one DLC or an amorphous carbon based layer, the layer being doped or not
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
  • C23C28/347—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with layers adapted for cutting tools or wear applications
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
  • C23C28/36—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including layers graded in composition or physical properties
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M57/00—Fuel-injectors combined or associated with other devices
  • F02M57/02—Injectors structurally combined with fuel-injection pumps
  • F02M57/022—Injectors structurally combined with fuel-injection pumps characterised by the pump drive
  • F02M57/025—Injectors structurally combined with fuel-injection pumps characterised by the pump drive hydraulic, e.g. with pressure amplification
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
  • F02M2200/90—Selection of particular materials
  • F02M2200/9038—Coatings

Definitions

• the present invention relates to thin film coatings for steel components used in fuel injectors, and more particularly for metal carbon material thin film coatings for low alloy steel or tool grade steel fuel injector needles.
• a fuel injector In direct injection diesel engine applications, a fuel injector is a precision device that must meter the quantity of fuel required for each cycle of the engine and must develop the high pressure necessary to inject the fuel into the combustion chamber at the correct instant of the engine operating cycle.
• Many fuel systems presently used in direct injection diesel engines utilize a hydraulically actuated and/or electronically controlled fuel injector to pressurize the fuel charge to obtain the desired fuel spray pattern and fuel volume into the combustion chamber at the precise moment.
• the many modern hydraulically actuated and/or electronically controlled fuel injectors often operate in a much more harsh or severe environment, in terms of operating temperatures, pressures, speeds, etc. than conventional fuel injectors.
• These hydraulically actuated and/or electronically controlled fuel injectors often use very compact and high precision moveable components such as the fuel injector needles, valves, and plungers to achieve the prescribed delivery of fuel at the desire time and for the desired duration.
• TiN coatings are usually applied at extremely high temperatures (e.g. about 450 degrees C) which may produce unwanted thermal stresses and related failures to the fuel injector components. It is also believed that TiN coatings on fuel injector needle tend to increase the wear of the needle mating component at the mating or seating location. In addition, TiN coatings tend to increase the overall cost of the fuel injector needle because the TiN coated fuel injector needle requires tool grade steel to withstand the high temperatures observed in the application of the TiN coating.
• the present invention aids in overcoming one or more of the aforementioned problems associated with the fuel injector needle members and satisfactorily addresses the shortcomings of the related art solutions to such problems.
• the invention may be characterized as a metal carbon material or diamond like carbon coated low alloy steel or tool grade steel component for a fuel injector, such as a fuel injector needle, having suitable hardness characteristics, improved boundary lubrication characteristics, and improved wear resistance characteristics.
• the fuel injector component such as a fuel injector needle or other contacting surface, comprises a low alloy steel or tool grade steel substrate and a primary thin film coating (e.g. titanium containing diamond like carbon, chromium containing diamond like carbon, or tungsten containing diamond like carbon) deposited on the low alloy steel or tool grade steel substrate.
• the primary coating preferably has a thickness generally no greater than about 2.0 microns.
• the preferred coating may also include a thin bond layer (e.g. less than 1.0 micron thick chromium layer) deposited between said low alloy steel or tool grade steel substrate and the primary metal carbon material coating.
• a further aspect of the present invention is the resulting hardness, boundary lubricity, and wear resistance characteristics of the coated steel substrate.
• the hardness of the metal carbon material coating is preferably greater than 1000 Kg/mm 2 as measured using a Hardness Knoop HDNS 50 gram load whereas the boundary lubricity and wear resistance characteristics of the coated substrate are generally improved over those of an non-coated steel substrate .
• FIG. 1 is a cross-sectional view of a fuel injector
• FIG. 2 is a side view of a coated fuel injection needle member in accordance with the present invention.
• FIG. 1 a hydraulically actuated, electronically controlled fuel injector 14 having a needle check valve coated in accordance with the present invention is shown.
• Injector 14 includes an injector body 15 having an actuation fluid inlet 50 that is connected to a branch rail passage, actuation fluid drains 52 and 54 that are connected to actuation fluid recirculation line 71 and a fuel inlet 60 connected to a fuel supply passage 66.
• Injector 14 includes a hydraulic means for pressurizing fuel within the injector during each injection event and a needle valve member 86 that controls the opening and closing of nozzle outlet 63.
• the hydraulic means for pressurizing fuel includes an actuation fluid control valve that alternately opens actuation fluid cavity 51 to the high pressure of actuation fluid inlet 50 or the low pressure of actuation fluid drain 52.
• the actuation fluid control valve includes a three-way solenoid 75 attached to a pin spool valve member 76.
• An intensifier spool valve member 78 responds to movement of pin spool valve member 76 to alternately open actuation fluid cavity 51 to actuation fluid inlet 50 or low pressure drain 52.
• the hydraulic pressurizing means also includes actuation fluid cavity 51 that opens to a piston bore 56, within which an intensifier piston 83 reciprocates between a return position (as shown) and a forward position.
• Injector body 15 also includes a plunger bore 58, within which a plunger 85 reciprocates between a retracted position (as shown) and an advanced position.
• a portion of plunger bore 58 and plunger 85 defines a fuel pressurization chamber 64, within which fuel is pressurized during each injection event.
• Plunger 85 and intensifier piston 83 are returned to their retracted positions between injection events under the action of compression spring 84.
• the hydraulic means for pressurizing fuel includes the fuel pressurization chamber 64, plunger 85, intensifier piston 83, actuation fluid inlet 50, actuation fluid cavity 51 and the various components of the actuation fluid control valve, which includes solenoid 75, pin spool valve member 76, ball check and intensifier spool valve member 78.
• fuel enters injector 14 at fuel inlet 60 and travels along fuel supply passage 66, past ball check valve 68 and into fuel pressurization chamber 64, when plunger 85 is retracting.
• Ball check 68 prevents the reverse flow of fuel from fuel pressurization chamber 64 into fuel supply passage 66 during the plunger's downward stroke.
• Pressurized fuel travels from fuel pressurization chamber 64 via a connection passage 69 to nozzle chamber 62.
• a needle valve member 86 moves within nozzle chamber 62 between an open position in which nozzle outlet 63 is opened and a closed position in which nozzle outlet 63 is closed. Needle valve member 86 is mechanically biased to its closed position by a compression spring 89.
• Needle valve member 86 includes opening hydraulic surfaces 87 exposed to fluid pressure within nozzle chamber 62 and a closing hydraulic surface 88 exposed to fluid pressure within a needle control chamber 72. Needle valve member 86 includes a needle portion 91 and intensifier portion 92 that are shown as separate pieces for ease of manufacturing, but both portions could be and are preferably machined as a single integral steel component .
• pressurized fuel acts upon the opening hydraulic surfaces 87 whereas actuation fluid acts upon the closing hydraulic surface 88.
• the closing hydraulic surface and the opening hydraulic surface are sized and arranged such that the needle valve member 86 is hydraulically biased toward its closed position when the needle control chamber is open to a source of high pressure fluid.
• needle valve member 86 When needle control chamber 72 is opened to a low pressure passage, needle valve member 86 performs as a simple check valve of a type known in the art, in that it opens when fuel pressure acting upon opening hydraulic surfaces 87 is greater than a valve opening pressure sufficient to overcome return spring 89.
• opening hydraulic surfaces 87 and closing hydraulic surface 88 are preferably sized and arranged such that the needle valve member is hydraulically biased toward its open position when the needle control chamber is connected to a low pressure passage and the fuel pressure within the nozzle chamber is greater than the valve opening pressure.
• the illustrated fuel injector needle valve includes a main body section, a lower section, and a loading end section.
• the various sections of the fuel injector needle 86 are formed or machined from a low alloy steel substrate or, more preferably, a tool steel substrate 95.
• the term "low alloy” as used herein means a steel grade in which the hardenability elements, such as manganese, chromium, molybdenum and nickel, collectively constitute less than about 3.5% by weight of the total steel composition. From an economic and reliability standpoint, a low alloy steel or tool steel substrate 95 is preferable for many fuel injector components, including the fuel injector needle and fuel injector nozzle.
• Composition of the primary coating 96 is preferably selected from the group consisting of metal carbon materials such as titanium containing diamond like carbon (DLC), tungsten-DLC, or chromium-DLC.
• the preferable metal carbon material is a tungsten-DLC such as tungsten-carbide containing carbon. Where tungsten- carbide containing carbon is used the tungsten content is graded, and thus may range at any given layer of between about 0% to about 100%, more preferably between about 15% and about 30%.
• a bond layer 98 of a chromium layer or other suitable metal layer to the steel substrate 95 to provide improved adhesion of the primary metal carbon material coating 96, if tungsten- carbide containing carbon is utilized as the primary coating.
• the optional bond layer material is preferably applied using a similar vapor deposition process to yield a bond layer 98 having a thickness of generally between about 0.05 micron and 0.5 micron.
• the coating thickness on the fuel injection needle valve member 86 should be fairly uniform as measured on a sample of the fuel injector needles by the Ball Crater Test at a plurality of locations on the needle.
• the primary metal carbon material coating has a thickness desirably no greater than about 2.0 microns and preferably has a thickness of between about 0.5 microns and about 1.7 microns.
• a primary coating thickness greater than about 2.0 microns is undesirable because the metal carbon thin film coating 96 may develop residual stresses high enough to separate the metal carbon thin film coating 96 from bond layer 98 or steel substrate 95.
• the thin film coating 96 may be applied to the entire length of the needle valve member substrate 95 or the coating 96 may be applied partially, to the lower end of the needle valve member.
• the needle valve member may be held by a small cup or retainer with a slightly larger diameter to hold the needle valve member in place during the coating process.
• the portion of the needle valve member to be coated is then exposed while the portion that is to be free from said coating would be disposed in and covered by the cup or retainer.
• the lower portion of the needle valve member proximate the fuel injector tip requires the thin film coating.
• the chromium bond layer 98 has a thickness desirably no greater than about 1.0 micron and preferably has a thickness of between about 0.05 micron and 0.5 micron and most preferably between about 0.1 and 0.3. As with the primary coating 96, a bond layer thickness greater than the aformentioned thickness is undesirable because the bond layer 98 may develop residual stresses high enough to separate from the steel substrate 95 or needle valve member.
• Control of some or all of the physical properties of the thin film coatings and coated substrate other than thickness are also important to producing a highly reliable needle member.
• coating adhesion, coating hardness, substrate hardness, surface texture, frictional coefficients are some of the physical properties that should be monitored.
• coating adhesion, coating hardness, substrate hardness, surface texture, frictional coefficients are some of the physical properties that should be monitored.
• the applied thin film coatings should be generally free of surface defects and have a specified surface texture ratings or surface texture measurements dependent on the environment, specifications, and intended use of the component.
• Surface defects are generally observed on a sample of the fuel injector needle members coated through the observation of multiple points on the surface of the coated samples at about 100. times magnification factor.
• the surface observations are generally compared to various classification standards to ensure the coatings are substantially free from surface defects as opposed to pin holes and substrate defects .
• the applied coatings should generally adhere to the steel substrate. Coating adhesion can be assessed for a given population of fuel injector needle members, for example, by using standard hardness tests (e.g. Rockwell C HDNS measurements).
• the coating hardness is also important characteristic of the fuel injector needle member.
• the applied tungsten-carbide containing carbon coating maintains a hardness of greater than 1000 Kg/mm 2 as measured using a Hardness Knoop HDNS 50 gram load.
• the substrate hardness after the coating process is preferably 75-79 RKW using a 30N hardness tester.
• the coated steel substrate desirably has a boundary lubricity value greater than the boundary lubricity value of the steel substrate as measured using the ISO 12156, version 1.3 HFRR (High Frequency Reciprocating Rig) .
• the coated steel substrate desirably has a friction coefficient less than about 0.5, and more preferably a friction coefficient no more than about 0.2 whereas the friction coefficient of the non- oxidized, non-coated steel component is typically 0.5 or greater. It is also desirable that the friction coefficient be about 0.2 because the beneficial effects of enhanced boundary lubrication will be offset by a substantial increase in the friction coefficient .
• any one of the vapor deposition techniques such as physical vapor deposition (e.g. sputtering), chemical vapor deposition and arc vapor deposition or hybrids thereof, can be employed to deposit the coatings on the low alloy steel or tool grade steel substrate.
• the preferred method used to apply the tungsten-carbide containing carbon coating should allows precise control over the amount of tungsten carbide in the thin film coating.
• the bond layer of chromium, utilized in conjunction with the tungsten-carbide containing carbon coating can be applied by sputtering or, more preferably, an arc vapor deposition (AVD) process.
• the arc source in arc vapor deposition, is adapted to impart a positive charge on the vapor generated.
• a negative bias voltage of a selected voltage e.g. 50 Volts
• a vapor deposition bond layer of chromium is thus deposited on the target substrate.
• Such arc vapor deposition coating methods utilizing an arc source to impart a positive charge on the vapor generated and a negative bias voltage to impart a negative charge on the substrate, are generally known in the art.
• the steel substrate is formed from an non- oxidized steel substrate that has been cleaned and prepared to facilitate bonding with the preferred coating or bond layer or both.
• the cleaning and the preparation of the steel substrate can be accomplished by conventional methods such as degreasing, grit blasting, etching, chemically assisted vibratory techniques, and the like.
• Such surface finishing techniques are well known to those skilled in the art.
• the preferred substrate surface finishing operations performed prior to the coating application include a grinding process to obtain a highly smooth surface, ultrasonic cleaning with an alkaline solution, and ion-etching of the substrate surface using argon.
• any heat treatment operations specified for the component are performed prior to coating applications .
• the thin film coating process further comprises the step of forming a solid lubricant coating on the substrate by arc vapor deposition or sputtering process.
• the preferred coating is tungsten carbide containing carbon because such coatings result in improved boundary lubrication with a reduction in friction of the lubricated contact.
• Arc vapor deposition (AVD) is the preferred method of depositing the coatings, and in particular the chromium bond layer, if used, on the steel substrate because the AVD process is carried out at temperatures in the range of 150-250°C or other temperatures which are below the tempering temperature of the selected grade steels.
• the sputtering process is generally performed at temperatures that have little residual effect on the steel substrates.
• the finished metal carbon material coating is preferably a uniform thickness (e.g. between about 0.5 micron and about 1.7 microns), smooth, adherent and free from visible defects. If used the preferred chromium bond layer is between about 0.05 and 0.5 microns thick.
• the disclosed thin film coatings for fuel injector components are particularly useful in highly loaded, marginally lubricated fuel injection system applications where component wear (both sliding and impact type) are typically encountered.
• the component comprises a steel substrate and diamond like carbon primary coating (e.g. tungsten carbide containing carbon) deposited on the substrate.
• the primary thin film coating has a thickness generally no greater than about 2 microns and more preferably, a thickness of between about 0.5 microns and about 1.7 microns.
• a bond layer of chromium or other suitable metal is applied to improve the adhesion properties of the primary thin film coating to the substrate.
• Applying a bond layer between the steel substrate and the primary thin film coating is generally known in art.
• the bond layer has a thickness of less than 1.0 microns and more preferably of between about 0.1 microns and about 0.3 microns.
• the actual thickness and other physical property characteristics of the coating are preferably tailored to the application and environment in which the fuel injection system is to be used.
• the use of the disclosed component coatings in such hostile fuel injection system applications provides advantages even after such coatings wear away. As may be expected, even the disclosed fuel injector component coatings wear over time and after continual use. However, as the coatings wear, the contacting surfaces of the underlying steel substrates exhibit corresponding wear patterns. Thus, even after the component coatings are no longer present, the contacting steel surfaces of the previously coated fuel injector components exhibit only marginal amounts, if any, wear.
• the disclosed coatings provide the added benefit of protecting the components from adhesive and abrasive wear much the same as a break-in coating would protect contacting surfaces.
• the illustrative example shows the beneficial effect of the diamond like carbon coatings deposited by sputtering on a low alloy steel or tool grade substrate.
• Accelerated wear tests were performed on Caterpillar fuel injector components operating within a Caterpillar Fuel Injector.
• the fuel injector needles contained in the tested fuel injectors included at least one with a tungsten carbide containing carbon thin film coating on a low alloy steel substrate (52100 Steel) , at least one with a tungsten carbide containing carbon thin film coating on a tool grade steel substrate (-M2).
• the wear test was a combined needle check and corresponding tip wear test that measures the protrusion change in microns. Generally, the lower protrusion change represents improved wear characteristics.
• the test samples were compared to wear tests for two baseline Caterpillar fuel injectors having no coatings applied to the needle valve member.
• the two baseline samples included a needle valve member one made from a low alloy steel substrate (52100 Steel) and one made from a tool grade steel (M2) .
• the Caterpillar Fuel Injectors were testing using direct injection of a Caterpillar fuel, 1E2820, which is a low lubricity diesel fuel. Eighteen 18 needles were utilized per test. The fuel injectors were tested for 125 hours and 250 hours before the wear comparisons were made.
• the tungsten carbide containing carbon coated fuel injector needles demonstrated very good wear resistance when pumping the low lubricity fuel as compared to the non-coated fuel injector needle of the same steel substrate.
• the needle check valve having a tool grade steel substrate and a tungsten carbide containing carbon thin film coating performed better than expected at the 250 hour test intervals. Comparative test results are given in the following table.
• the present invention thus provides a coating or surface treatment for fuel injection system components such as fuel injector needles. While the invention herein disclosed has been described by means of specific embodiments and processes associated therewith, numerous variations can be made thereto by those skilled in the art without departing from the scope of the invention as set forth in the claims or sacrificing all its material advantages.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Combustion & Propulsion (AREA)
• General Engineering & Computer Science (AREA)
• Fuel-Injection Apparatus (AREA)

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• 2000
  • 2000-02-15 WO PCT/US2000/040001 patent/WO2001061182A1/en active Application Filing
  • 2000-02-15 EP EP00904657A patent/EP1177375A1/de not_active Withdrawn

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