Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/02—Parts of sliding-contact bearings
  • F16C33/04—Brasses; Bushes; Linings
  • F16C33/06—Sliding surface mainly made of metal
  • F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
  • F16C33/121—Use of special materials
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0433—Nickel- or cobalt-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
  • C22C1/059—Making alloys comprising less than 5% by weight of dispersed reinforcing phases
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0089—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with other, not previously mentioned inorganic compounds as the main non-metallic constituent, e.g. sulfides, glass
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
  • F01D25/16—Arrangement of bearings; Supporting or mounting bearings in casings
  • F01D25/166—Sliding contact bearing
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/12—Blades
  • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2201/00—Metals
  • F05C2201/04—Heavy metals
  • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
  • F05C2201/0463—Cobalt
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2201/00—Metals
  • F05C2201/04—Heavy metals
  • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
  • F05C2201/0466—Nickel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2220/00—Application
  • F05D2220/40—Application in turbochargers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/50—Bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2300/00—Materials; Properties thereof
  • F05D2300/10—Metals, alloys or intermetallic compounds
  • F05D2300/13—Refractory metals, i.e. Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W
  • F05D2300/132—Chromium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C2360/00—Engines or pumps
  • F16C2360/23—Gas turbine engines
  • F16C2360/24—Turbochargers

Definitions

• the present invention relates to alloys based on cobalt and/or nickel and a method for the production thereof by a powder metallurgy route.
• Turbochargers for internal combustion engines have been in common use for many years in order to increase the power output and decrease the emissions of an engine.
• one drawback with the use of turbochargers has been the so-called “turbo lag" where the engine speed response to the throttle is delayed owing to the time needed for the exhaust gas turbine to increase speed and hence supply further air by the compressor for combustion.
• turbocharger designs have been introduced which have largely overcome or at least greatly reduced the turbo lag problem.
• Turbochargers are used on both gasoline and diesel oil fuelled vehicles. Generally, turbochargers for gasoline engines run at a higher temperature than do turbochargers for diesel oil fuelled vehicles. Furthermore, due to the superior fuel efficiency of diesel engines, there is an increasing drive to employ turbocharged diesel engines in mass produced "family" type vehicles. Effectively, such diesel powered vehicles are intended to drive and behave in a manner substantially indistinguishable from gasoline fuelled vehicles including the performance thereof.
• turbochargers in gasoline engines run at a higher temperature than those for diesel engines and furthermore, the general temperature levels for both types are rising as overall engine performance increases.
• the unlubricated bearing or bush is primarily required to have good oxidation resistance at its operating temperature rather than high creep resistance, as required in rotating parts such as blades for gas turbine engines, for example. Furthermore, internal defects such as relatively high levels of porosity, prior particle boundaries and grain boundary precipitates may be allowable.
• a sintered material comprising an alloy selected from one of the groups having a composition comprising in weight%: either Cr 5- 30/Mo 0-15/Ni 0-25/ 0-15/C 0-5/Si 0-5/B 0-5/Fe 0-5/Mn 0- 5/total others lOmax/Co balance, or Cr 10-20/Mo 0-15/Co 0-20/W 0-5/Fe 0-20/Al 0-5/Ti 0-5/total others 15max/Ni balance; said alloy having incorporated therein from 3-15 weight% of Sn; and optionally from 1-6 weight% of a solid lubricant.
• the “total other” elements in the cobalt-based alloy may include Si, Mn, Cu, V, Nb, Al and Ta.
• the “total other” elements in the nickel-based alloy may include C, Si, V, Mn, B, Hf, Zr, Nb and Ta.
• the solid lubricant may comprise molybdenum disulphide and/or tungsten disulphide for example.
• the material according to the first aspect of the present invention may also possess up to about 10 vol% of porosity.
• a method of making a material comprising the steps of: mixing a powder of an alloy selected from the group having a composition comprising in weight%: either Cr 5-30/Mo 0-15/Ni 0-25/W 0-15/C 0-5/Si 0-5/B 0-5/Fe 0-5/Mn 0-5/total others lOmax/Co balance, or Cr 10-20/Mo 0-15/Co 0-20/ 0-5/Fe 0- 20/A1 0-5/Ti 0-5/total others 15max/Ni balance with from 3-15 weight% of Sn powder and optionally with from 1-6 weight% of a solid lubricant; compacting said powder mixture to form a green compact; and, sintering said green compact in a controlled environment.
• the cobalt-based or nickel-based alloy is in pre-alloyed form.
• the powder mixture prior to compaction and sintering will preferably comprise particles of the pre-alloyed cobalt- or nickel- based powder, the tin powder and optionally particles of the solid lubricant .
• the tin content lies in the range from 4 to 10 weight%.
• tin content acts as a powder pressing aid, acting as a die and powder particle lubricant thus, enabling higher green densities and hence strengths to be achieved at any given pressing pressur .
• the solid lubricant may include molybdenum disulphide and/or tungsten disulphide, however, any solid lubricant powder known to be effective at high operating temperatures and able to withstand the sintering step may be employed.
• the material and method of the present invention employ a so-called dry lubricating material such as tungsten disulphide or molybdenum disulphide; firstly, because the service applications intended for the materials are in high-temperature environments where conventional oil lubrication is not. possible and, secondly because the sulphur content of these materials appears to have a beneficial effect on their production.
• the tungsten and/or molybdenum disulphide phase partially dissociates at the sintering temperature, and under the ambient conditions of a gas sintering atmosphere at substantially atmospheric pressure, liberating some free sulphur which, in the presence of liquid tin, seems to promote the diffusion of cobalt through the structure as evidenced by SEM EDAX analysis. Tin has been found deep inside prior cobalt alloy particles and substantial amounts of cobalt in the once-liquid phase.
• a preferred range of solid lubricant may lie in the range from 2 to 4 weight%.
• tin powder is mixed with the cobalt- based or nickel -based alloy powder to provide liquid phase sintering, the tin having the effect of producing a liquid phase at a sintering temperature of 1170°C and below and also using conventional high-volume production equipment such as continuous throughput conveyor furnaces and the like.
• Such furnaces may be mesh belt or walking beam furnaces, for example, and utilise flowing protective or reducing gas atmospheres comprising hydrogen and nitrogen mixtures, for example, at substantially atmospheric pressure. Such furnaces generally have a maximum operating temperature capability of about 1200°C. However, batch furnaces using vacuum or gas atmospheres may be used if desired.
• the liquid phase serves to promote diffusion and consequent densification of the pressed article.
• the initial liquid tin phase reacts with the cobalt-based or nickel-based alloy and diffuses into the green pressing and is itself eventually absorbed into the solid by reaction therewith so as to produce a rigid skeleton of re-arranged prior particles with a once-liquid phase filling the spaces of the skeleton. Inter-particle-necking between the prior particles is produced.
• Liquid phase forms as the tin melts at around 232 °C on heating to the sintering temperature.
• the liquid tin becomes enriched in cobalt as heating progresses until the final sintering temperature is reached, leaving a volume fraction of liquid proportional to the original mass fraction of tin added.
• the liquid solidifies eutectically on cooling at around 1112 °C.
• At least a proportion of the cobalt-based or nickel-based powder be of irregular particle shape. Where all of the powder is of substantially regular shape, such as rounded particles for example, it is not possible to achieve sufficient green strength to permit handling and survive die-ejection.
• pre-alloyed cobalt- or nickel-based pre-alloyed powder may be mixed together in the same powder mixture prior to compaction and sintering. Additionally or alternatively there may be a proportion of one powder having irregularly shaped particles and a proportion of the same or a different pre-alloyed powder composition having regular shaped powder particles.
• tin in such expensive alloys as nickel -based and cobalt-based alloys is something which is generally contrary to the teachings of the prior art. Such alloys are frequently used for extremely arduous applications such as blades, rotors and stators in gas turbine engines, for example.
• the presence of tin and other low melting point elements in such components is something which is normally specifically excluded, or limited to a maximum of about 15 parts per million, for example, on the ground that tin forms relatively low melting point grain boundary phases which seriously weakens highly stressed parts resulting in inter alia lower creep rupture strengths.
• Such alloys produced by these companies are used for the applications as described above (HIPped) and also for hard-facing, oxidation resistant uses and applied, for example, by plasma spraying and the like.
• Examples of such commercially available alloys may include Stellite 31 (trade name) , Tribaloy T-400 (trade name) and Metco 45VF- NS (trade name) .
• the present invention provides both a material, and a method for the production thereof, able to withstand the intended service environment and able to be produced in high volumes on existing high volume production plant at an economic cost unlike prior art cobalt-based and nickel-based materials.
• a bearing for a turbocharger when made of the material of the first aspect of the present invention.
• a bearing for a turbocharger when made by the method of the second aspect of the present invention.
• examples will now be described by way of illustration only.
• the drawing shows a graph of shrinkage vs tin content for examples of materials according to the present invention which also contain varying levels of molybdenum or tungsten disulphide.
• Atomised powder of Tribaloy T-400 (trade name) was mixed for 20 minutes in a Y-cone blender with 10wt% of tin powder and 3.5wt% of molybdenum disulphide powder. 1.5wt% of a fugitive die lubricant, Kenolube (trade name) , was also added.
• the blended powder was uniaxially cold pressed at 770 MPa and sintered in a walking beam furnace for approximately 15 minutes at 1170°C with an atmosphere of 90% nitrogen: 10% hydrogen. Visual and SEM- EDAX analysis revealed that original particle boundaries are not visible and particle shape cannot be determined.
• the microstructure consisted of Co-Mo-Cr particles approximately 12 microns in diameter in a matrix of Co- Mo-Cr-Sn, with a Co-Sn-Mo-Cr phase at particle boundaries having the appearance of solidified liquid.
• a Cr-S phase was present as a discrete 10 micron sized phase.
• Atomised powder of Metco 45VF-NS (trade name) was mixed for 20 minutes in a Y-cone blender with 5wt% of tin powder and 2wt% of molybdenum disulphide powder. 1.5wt% of Kenolube (trade name) die lubricant was also added.
• the blended powder was uniaxially cold pressed at 770MPa and sintered in a walking beam furnace for approximately 15 minutes at 1170°C with an atmosphere of 90% nitrogen: 10% hydrogen.
• Visual and SEM-EDAX analysis revealed that original particle shape can be determined with particles having the composition Co-Cr-Ni-W-Sn.
• Inter-particle bonding had taken place the boundaries having 5 micron sized precipitates of Cr-Co-W-Ni-Mo and Cr-S-Sn-Co-Ni, with a Sn-Ni-Co-Cr phase having the appearance of solidified liquid. Within the particles there were 5 micron precipitates of Cr-Co-W-Ni-Mo .
• Atomised powder Stellite 31 (trade name) was mixed for 20 minutes in Y-cone blender with 7.5wt% of tin powder and 3.5wt% of molybdenum disulphide powder. 1.5wt% of Kenolube (trade name) die lubricant was also added. The blended powder was uniaxially cold pressed at 770MPa and sintered in a walking beam furnace for approximately 15 minutes at 1170°C with an atmosphere of 90% nitrogen: 10% hydrogen. Visual and SEM-EDAX analysis revealed that original particle boundaries were visible due to the formation of precipitates.
• the particles were composed of Co-Cr-Ni-W-Fe-Sn and the precipitates were a mixture of Cr-S and Cr-W-Co-Mo, with a Sn-Ni-Co-Cr phase having the appearance of solidified liquid.
• Atomised powder Stellite 31 (trade name) was mixed for 20 minutes in Y-cone blender with 7.5wt% of tin powder and 3.5wt% of tungsten disulphide powder. 1.5wt% of Kenolube
• the drawing shows a graph of percentage shrinkage of the overall diameter (OD) .
• tin powder blended with the respective cobalt alloy powder which, in all cases, is Stellite 31 (trade name) .
• the Stellite 31 powder has been blended with the appropriate amount of tin powder and also the stipulated amount of molybdenum disulphide or tungsten disulphide according to the legend.
• the Stellite 31 powder was mixed with the appropriate amount of tin and molybdenum-disulphide or tungsten-disulphide, together with 1.5 t% of Kenolube (trade name), as a die lubricant.
• the sulphur can also promote formation of liquid with Co in a similar fashion to Sn. It is believed that once the tin content reaches about 10wt%, then the quantity of liquid phase present is sufficient to promote diffusion and densification without the need for the sulphur containing solid lubricant compound in this regard. However, it is believed that the presence of such a solid lubricant compound in the structure assists the bearing sliding characteristics in the application, especially where the presence of a conventional liquid lubricant is not possible.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Powder Metallurgy (AREA)
• Chemically Coating (AREA)
• Lubricants (AREA)
• Chemical Treatment Of Metals (AREA)
• Materials For Medical Uses (AREA)
• Contacts (AREA)
• Laminated Bodies (AREA)
• Sliding-Contact Bearings (AREA)
• Ceramic Capacitors (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

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Cited By (3)

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Citations (2)

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• 2001
  • 2001-07-03 GB GBGB0116203.1A patent/GB0116203D0/en not_active Ceased
• 2002
  • 2002-06-25 JP JP2003510468A patent/JP2004533543A/ja active Pending
  • 2002-06-25 DE DE60206632T patent/DE60206632T2/de not_active Expired - Lifetime
  • 2002-06-25 EP EP02782469A patent/EP1412547B1/en not_active Expired - Lifetime
  • 2002-06-25 AT AT02782469T patent/ATE306567T1/de not_active IP Right Cessation
  • 2002-06-25 US US10/482,253 patent/US6958084B2/en not_active Expired - Fee Related
  • 2002-06-25 GB GB0329418A patent/GB2392168B/en not_active Expired - Fee Related
  • 2002-06-25 WO PCT/GB2002/002911 patent/WO2003004711A1/en not_active Ceased

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