Classifications

• • 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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/20—Carburising
  • C23C8/22—Carburising of ferrous surfaces
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
• • 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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/24—Nitriding
  • C23C8/26—Nitriding of ferrous surfaces
• • 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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
  • C23C8/30—Carbo-nitriding
  • C23C8/32—Carbo-nitriding of ferrous surfaces

Definitions

• the present invention concerns an alloy particularly suitable for use in the manufacture of mechanical parts, which are thermally highly stressed and exposed to oxidizing and/or corroding gasses.
• the invention also concerns an exhaust-gas turbine of a turbocharger having a nozzle ring formed of the inventive alloy arranged in the inflow passage of the exhaust- gas turbine .
• Turbochargers use the exhaust gasses discharged from an internal combustion engine as a motive gas to rotate a turbine wheel, which is mounted on one end of a shaft.
• a compressor wheel is mounted on the other end of the shaft, and is turned by the turbine wheel to compress air, which is then communicated to the engine, thereby supplying charge air to the engine for increasing engine performance.
• a nozzle ring located in an exhaust-gas turbine of a turbocharger is subjected to severe stresses due to fluctuating operating conditions, i.e., increases or reductions in the pressure and temperature of the working medium.
• the working medium may have a large temperature gradient . Since a nozzle ring has only a small mass compared with the turbine components surrounding it, it is subjected to relatively pronounced thermal expansions.
• the nozzle ring and the walls of the turbocharger turbine entrance throat must be of a material which is highly corrosion resistant, to prevent sticking or binding of the vanes.
• Increasing longevity requirements e.g., one million miles for commercial diesel vehicles
• the iron-aluminum alloy comprises the following constituents in atom percent: 12-18 aluminum; 0.1-10 chromium; 0.1-2 niobium; 0.1-2 silicon; 0.1-5 boron; 0.01-2 titanium; 100-500 ppm carbon; 50-200 ppm zirconium; and remainder iron. While this alloy is distinguished by the fact that its constituents are limited to metals which are comparatively inexpensive and are available independently of strategic political influences, the alloy does not meet the extended life requirements expected of modern commercial diesel engines or even automobiles. Further, there is a demand for parts capable of operating at even higher temperatures.
• a turbocharger including a turbine housing with a variable geometry mechanism which controls the flow area of the throat through which motive exhaust gasses are communicated to the turbine wheel.
• the turbine housing is provided with an insert which defines one wall of the throat and which is cast in place as part of the turbine housing.
• the insert may be made of a relatively expensive, high nickel content material such as D5B NI-RESIST, which has a very high nickel content as compared to standard ductile iron, and on this basis has enhanced corrosion resistance properties to assure that a non- corrosive surface is provided adjacent to the vanes which are pivotally actuated to vary the area of the throat.
• the remainder of the housing is made of a standard ductile iron, which is substantially less expensive than the more expensive corrosion resistant high nickel content material from which the insert is manufactured.
• an iron- based alloy that contains the elements of cobalt, carbon, silicon, manganese, chromium, which optionally contains the further elements molybdenum, niobium, and tungsten, and optionally also minor amounts of one or more of aluminum, nickel, vanadium, nitrogen, sulfur and titanium, on the condition that the combined amount of chromium and cobalt is at least 18 percent by weight of the total alloy, preferably at least 34.5 percent by weight, most preferably at least 36 percent by weight and at most 46 percent by weight, preferably not more than 41.5 percent by weight of the total alloy, the remainder being iron and metallurgically suited admixtures for the production of an alloy particularly suitable for use in mechanical parts which are thermally highly stressed and exposed to oxidizing and/or corroding effects.
• Another aspect of the present invention is in the manufacture of devices and machines subject to highly corrosive gasses, wherein the machine part is manufactured from an iron based alloy, preferably a stainless steel alloy, containing the elements of cobalt, carbon, silicon, manganese, chromium, further optionally containing at least one of the elements molybdenum, niobium, tungsten, nickel and sulfur, provided that the combined amount of chrome and cobalt is at least 18 percent by weight, most preferably at least 34.5 percent by weight, and most preferably at least 36percent by weight of the total alloy, and at most 46 percent by weight, preferably at most 41.5 percent by weight of the total alloy.
• an iron based alloy preferably a stainless steel alloy
• the elements of cobalt, carbon, silicon, manganese, chromium further optionally containing at least one of the elements molybdenum, niobium, tungsten, nickel and sulfur, provided that the combined amount of chrome and cobalt is at least 18 percent by weight, most
• the alloy according to the present invention undergoes some amount of oxidation when used as a nozzle ring in a variable geometry turbocharger, it is surprising that oxidation occurs only to the extent that oxides work in combination with soot particles in the exhaust gasses passing through the turbocharger to provide a lubricating effect for pivoting nozzle blades. Accordingly, the nozzle ring, guiding stones and rollers formed according to the present invention are "self lubricating" and suffer less binding or jamming defect compared to state of the art nozzle rings.
• a further surprising advantageous property of nozzle rings, guiding stones and rollers formed according to the present invention is that their thermal coefficient of expansion (alpha value) is from about 14 to about 15.5 at 700°C.
• nozzle rings according to the present invention can be used in any turbocharger, with no particular consideration having to be paid to turbocharger materials.
• the alloy is characterized by fine grain structure, intermetallic phase development, the formation of cobalt oxides, and improved tribological characteristics.
• the iron-based alloy preferably comprises C: 0.25-0.6% by weight, Si: 0.0 - 4.0% by weight, Mn: 0.0 - 3.0% by weight, Cr: 14 - 28% by weight, and Co: 2 - 18% by weight.
• the iron-based alloy according to the invention may alternatively comprise C: 0.4 - 0.6% by weight, Si: 3.0 - 4.0% by weight, Mn: 0.0 - 2.0% by weight, Cr: 14.0 - 18.0% by weight, Co: 6.0 - 8.0% by weight, and additionally comprises Mo: 1.8 - 2.2% by weight, Nb : 1.8 - 2.2% by weight, Ni : 0.0 - 0.5 % by weight, and S: 0.0 - 0.035 % by weight.
• the iron-based alloy according to the invention may comprise C: 0.25 - 0.35% by weight, Si: 3.0 - 4.0% by weight, Mn: 1.5 - 2.0% by weight, Cr: 16.0 - 20.0% by weight, Co: 2.0 - 3.0% by weight, and additionally comprises Ni : 0.0 - 0.5 % by weight, and S: 0.2 - 0.4 % by weight.
• a martensitic structure including at most 10% ferrite of normalized tempered steel is preferable.
• an iron-based alloy comprising: C: 0.25 - 0.6% by weight, Si: 0.0 - 4.0% by weight, Mn: 0.0 - 3.0% by weight, Cr: 14 - 28% by weight, and Co: 2 - 18% by weight; measured as a percentage of total weight of the alloy; wherein a total concentration of C and, if present, N is at no greater than about 1.2%; and the remainder of the alloy comprising iron and metallurgically suited admixtures for the production of machine parts that in their function are exposed to severe thermal stress and oxidizing or corrosive effects.
• a process of integrating the iron-based alloy in a machine includes manufacturing at least one machine part from the iron- based alloy and installing the same to function under conditions of severe thermal stress and oxidizing or corrosive effects .
• a process of making a machine part for functioning under conditions of severe thermal cycling and in a corrosive environment includes: forming the machine part from an iron-based alloy most preferably comprising: C: 0.35 - 0.45% by weight, Si: 0.0 - 1.0% by weight, Mn: 0.0 - 2.0% by weight, Cr: 21 - 25% by weight, Co: 13.5 - 16.5% by weight, Mo : 1.8 - 2.2% by weight, Nb : 2.8 - 3.2% by weight, W: 2.3 - 3.0% by weight, measured as a percentage of total weight of the alloy; optionally tempering the machine part; and further optionally forming a hardened layer on at least a portion of a surface of the machine part.
• the hardened layer may be made by forming a nitride layer on at least a portion of the machine part, or by forming a carbonitride layer on at least a portion of the machine part . Further, the hardened layer may be vapor deposited (PVD or CVD) as an aluminum-based carbide layer, a titanium-based carbide layer, an aluminum-based nitride layer, a titanium-based nitride layer, an aluminum-based oxide layer, or a titanium- based oxide layer. If machine parts are at least partly provided with a coating of hard material, especially favorable (i.e., low) friction values are attainable. However, for specific applications such as a nozzle ring for a turbocharger, there has not been found to be any need for a hardened layer.
• the alloy according to the invention is distinguished by excellent thermal shock resistance and can therefore be used particularly advantageously in those parts of thermal installations which are subject to thermal cyclic loading, such as, in particular, as a casing or casing part of a gas turbine or of a turbocharger or as a nozzle ring, in particular for a turbocharger. Due to the superb corrosion resistance to exhaust gas flow and improved durability despite thermal stress, the present iron-based alloys are favorable for use in making turbocharger nozzle rings, guiding stones and rollers .
• Manganese (Mn) is an element that improves the hardenability of the steel material. Mn acts not only as a de-oxidation agent with Si, but also as an agent for preventing segregation of S by stabilizing S in the molten metal by combining with it to form MnS . Further, Mn increases the strength and toughness of martensite after heat treatment (taking the place of or supplementing Ni, as will be explained later) . If the Mn content is less than 0.1%, the above effects are hardly realized, and if it exceeds 3%, it increases the amount of austenite remaining, decreases flowing characteristics of molten metals and decreases the strength. Especially, a content of at least 0.25% is preferable, and more preferably in the range of 0.5-2.0%.
• the alloy 46-50 HRC was solution annealed 1 h at 1150 -
• Grain Structure Duplex steel with very, very fine grain, with
• turbocharger nozzle ring has been described herein with great detail with respect to an embodiment suitable for the automobile or truck industry, it will be readily apparent that the novel alloy and the process for production of machine parts using the alloy are suitable for use in a number of other applications, such as turbine engines, power plants, etc.
• this invention has been described in its preferred form with a certain of particularity with respect to an automotive internal combustion turbocharger nozzle ring, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of structures and the composition of the combination may be resorted to without departing from the spirit and scope of the invention.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Supercharger (AREA)
• Control Of Turbines (AREA)

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• 2002
  • 2002-09-16 EP EP02773389A patent/EP1540024A1/de not_active Withdrawn
  • 2002-09-16 US US10/495,807 patent/US20050006006A1/en not_active Abandoned
  • 2002-09-16 JP JP2004535371A patent/JP2005539138A/ja active Pending
  • 2002-09-16 WO PCT/US2002/029284 patent/WO2004024970A1/en active Application Filing

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