WO2021150549A1 - Processus et systèmes pour un traitement de surface rapide - Google Patents

Processus et systèmes pour un traitement de surface rapide Download PDF

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Publication number
WO2021150549A1
WO2021150549A1 PCT/US2021/014092 US2021014092W WO2021150549A1 WO 2021150549 A1 WO2021150549 A1 WO 2021150549A1 US 2021014092 W US2021014092 W US 2021014092W WO 2021150549 A1 WO2021150549 A1 WO 2021150549A1
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Prior art keywords
sample
plasma
generation region
plasma generation
inner cavity
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PCT/US2021/014092
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English (en)
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Devendra Kumar
Satyendra Kumar
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Devendra Kumar
Satyendra Kumar
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Publication of WO2021150549A1 publication Critical patent/WO2021150549A1/fr

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    • 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
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/50—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges
    • C23C16/511—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges using microwave discharges
    • 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
    • C23C8/02—Pretreatment of the material to be coated
    • 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
    • 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
    • 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
    • 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
    • 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
    • C23C8/36—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 using ionised gases, e.g. ionitriding
    • 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
    • C23C8/80—After-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32192—Microwave generated discharge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32431—Constructional details of the reactor
    • H01J37/3244—Gas supply means

Definitions

  • the present application is directed to system and methods for rapid surface treatment of metals and alloys using atmospheric microwave plasma
  • Conventional furnaces that require the sample to be processed in elevated temperatures endure slow heating rates, which introduces undesired grain growth in the bulk of the sample material, which may result in the degradation of the material properties of the sample, such as, but not limited to, the strength of the material.
  • Conventional furnaces include a conveyer belt system for gradually increasing the surface temperature (arid the bulk temperature of the sample), which takes an extended period of time to achieve the desired processing temperature before exposure to potential for diffusion.
  • steel alloy gears may be placed on the belt to be heated to a specific processing temperature before exposure to a carbon potential for carburization.
  • a method for surface treatment of a sample includes placing the sample on a sample holder of a microwave plasma reactor including a reactor housing defining an inner cavity therein including the sample holder, and covering the sample with a ceramic cover to create a plasma generation region around the sample.
  • the method further includes evacuating the inner cavity and the plasma generation region via an outlet tube extending from outside the housing to the plasma generation region, and flowing a treatment gas to the plasma generation region via an inlet tube from outside the housing to the plasma generation region to create a potential.
  • the method also includes activating microwave power to generate a uniform microwave field around the plasma generation region and generate plasma within the plasma generation region and heating the plasma via the microwave field to treat the surface of the sample,
  • the heating may conducted at up to 1 ,000°C per minute via the microwave power being applied at up to 500 kW.
  • the plasma is generated within the plasma generation region in under 1.5 milliseconds after activating the microwave power.
  • placing the sample may further include placing a catalyst within the microwave plasma reactor such that the catalyst interacts with the microwave field to generate the plasma.
  • flowing the treatment gas may be for nitriding, carburizing, or boronization of the sample,
  • the sample may be a titanium alloy, and the treatment gas Is nitrogen.
  • the method may further include backfilling the inner cavity with an inert gas after the evacuating to return the inner cavity to atmospheric pressure.
  • the ceramic cover may be mullite, silicon nitride, or other high temperature ceramic material thermally stable up to 1750°C.
  • a system for rapid surface treatment includes a microwave plasma reactor housing having a top portion defining a top inner cavity therein and a bottom portion defining a bottom inner cavity therein and one or more magnetron ports for supplying microwave radiation to the microwave plasma reactor housing, with the top portion including a sample holder for receiving a sample to be treated, and the top inner cavity being separated and sealed from the bottom inner cavity by a solid plate.
  • the system further includes a ceramic cover positionable on the sample holder over the sample to form a plasma generation region therein, an inlet tube extending from outside the housing through the bottom inner cavity and exposed to the plasma generation region through an inlet aperture defined in the solid plate, and an outlet tube extending from outside the housing through the bottom inner cavity and exposed to the plasma generation region through an outlet aperture defined in the solid plate.
  • the system also includes electrical tubing extending from outside the housing through fire bottom inner cavity and exposed to the plasma generation region, the electrical tubing configured to apply a DC bias to the plasma generation region, The plasma is generated in the plasma generation region and confined around the sample via the DC bias applied, and the plasma is heated via the microwave radiation within the top inner cavity.
  • the bottom inner cavity may include ceramic insulation around the inlet tube and the outlet tube.
  • the bottom portion may include a ceramic plate towards a top end of the bottom portion, the ceramic plate allowing microwave radiation to penetrate therethrough, with the bottom inner cavity including the ceramic insulation beneath the ceramic plate, above the ceramic plate, or both.
  • the ceramic cover may be mullite, silicon nitride, or other high temperature ceramic material thermally stable up to 1750°C.
  • the magnetron ports are staggered about a periphery of the bottom portion, a height of the bottom portion, or both, and supply the microwave radiation from magnetrons at up to 500 kW.
  • the top portion of the housing may include a body component having an inner surface with a ceramic liner facing the top inner cavity, and an outer surface opposite the inner surface including ceramic insulation for limiting heat loss from the top inner cavity.
  • gas is provided via the inlet tubing for minding, carburizing, or boronization of the sample while the top inner cavity and the plasma generation region is at atmospheric pressure.
  • the microwave field may heat the plasma in the plasma generation region at up to 1000°C per minute.
  • the plasma generation region may further include a catalyst therein for interacting with the microwave field to generate the plasma,
  • a system for rapid surface treatment includes one or more magnetrons for generating microwave radiation of up to 500 kW, collectively; and a microwave plasma reactor having a housing defining a cavity including a sample holder therein for supporting a sample to be treated, and a ceramic cover positionable on the sample holder over the sample to define a plasma generation region therein around the sample within the cavity.
  • the microwave plasma reactor further includes an inlet tube extending from outside the housing and exposed to the plasma generation region; an outlet tube extending from outside the housing and exposed to the plasma generation region; and electrical tubing extending from outside the housing and exposed to the plasma generation region, the electrical region configured to apply a DC bias to the plasma generation region, Upon activation of the magnetrons, plasma is generated in the plasma generation region and heated at up to 1000 degrees C per minute and confined near a surface of the sample via the DC bias to harden the surface of the sample.
  • the sample holder may be a plurality of ceramic discs stacked within the housing, each of the plurality of ceramic discs defining apertures therethrough corresponding to each of the inlet tube, the outlet tube, and the electrical tubing.
  • a catalyst may be included within the plasma generation region to interact with the microwave radiation to generate the plasma.
  • FIG, 1A is a perspective view of an atmospheric microwave plasma furnace, according to an embodiment
  • FIG. 1B is a schematic cross-sectional illustration of the atmospheric microwave plasma furnace of FIG. 1A, taken along A -A’;
  • FIG. 1 C is a bottom view of the atmospheric microwave plasma furnace of FIG. 1 A;
  • FIG. 2 is a schematic perspective view of a furnace for an atmospheric plasma reactor with the chamber cavity closed, according to another embodiment
  • FIG, 3 is a schematic perspective view of the furnace of FIG. 2 with the chamber cavity open;
  • FIG. 4 is a schematic cross-sectional view of the atmospheric microwave plasma reactor of FIGS. 2-3;
  • FIG. 5 is a flow chart of a method of treating a surface of a sample, according to an embodiment.
  • integer ranges explicitly include all intervening integers.
  • the integer range 1-10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.
  • the range 1 to 100 includes 1, 2, 3, 4, , . . 97, 98, 99, 100.
  • intervening numbers that are increments of the difference between the upper limit and the lower limit divided by 10 can be taken as alternative upper or lower limits. For example, if the range is 1.1 , to 2.1 the following numbers 1.2, 1.3, 1.4, 1.5, 1 .6, 1.7, 1.8, 1.9, and 2.0 can be selected as lower or upper limits.
  • concentrations, temperature, and reaction conditions can be practiced with plus or minus 50 percent of the values indicated rounded to three significant figures.
  • concentrations, temperature, and reaction conditions e.g., pressure, pH, flow rates, etc.
  • concentrations, temperature, and reaction conditions can be practiced with plus or minus 30 percent of the values indicated rounded to three significant figures of the value provided in the examples.
  • concentrations, temperature, and reaction conditions e.g., pressure, pH, flow rates, etc.
  • concentrations, temperature, and reaction conditions e.g., pressure, pH, flow rates, etc.
  • systems and methods for rapid surface hardening of a sample is provided.
  • the systems and methods for rapid surface hardening according to the embodiments described herein limit the grain growth within the bulk of the material, thus limiting the reduction in strength of the sample while the surface is treated.
  • the surface of the sample is rapidly heated (e.g., reaching 750 to 1250 °C in 5 minutes or less), and is also exposed to a higher number of species available for diffusion during the surface hardening treatment.
  • the plasma surrounds the sample uniformly, irrespective of the shape of the sample, every exposed surface of the sample undergoes uniform surface treatment while limiting the grain growth within the bulk of the material.
  • Tints provide rapid and uniform heating for the plasma environment for treating the sample.
  • Pick ’ s Saw tiie rate of diffusion into the surface of the sample depends on the temperature and concentration gradient of the species.
  • Tints rapidly and uniformly heating the surface of the sample and generating a higher number of species for diffusion allows for a more favorable and even rate of diffusion on all surfaces of the sample, while limiting undesired grain growth within the bulk material of the sample.
  • an atmospheric microwave plasma furnace 100 is shown, according to an embodiment.
  • the atmospheric microwave plasma furnace 100 or interchangeably referred to as atmospheric microwave plasma reactor 100, houses a sample 200 comprising a bulk material 210 and with a surface 220 as the collective surface of various exterior surfaces of the bulk material 210.
  • furnace 100 and reactor 100 may be used interchangeably, as describing the collective system for rapid surface treatment having a furnace element and a structure for treating the sample therein.
  • the surface 220 of the sample 200 is treated within the furnace 100, such that the surface 220 is rapidly heated via microwave plasma and within a uniform environment (e.g,, based on a time-average field of microwaves) with a higher concentration of species to evenly harden the surfaces 220 of the sample 200, whi le grain growth is minimized within the bulk material 210.
  • a uniform environment e.g,, based on a time-average field of microwaves
  • the surface 220 of the sample 200 is heated and treated using microwave plasma at atmospheric pressure (i.c., at or near 101.325 kPa), allowing the sample 200 to be any material, such as, but not limited to, metals, ceramics, composites, and the like.
  • atmospheric pressure i.c., at or near 101.325 kPa
  • the embodiments described herein refer to atmospheric pressure, this is not intended to be limiting and it is contemplated that the surface treatment described is applicable in other pressures as well, including, but not limited to the mTorr range or up to 3 atmospheres (e.g., 0.50 to 3 atmospheres) as well.
  • Plasma within the reactor dissociates molecules in the precursor gas (e.g., nitriding will be described as an example below, where precursor gases for nitriding include ammonia and nitrogen gas) to provide an atomic species.
  • precursor gases for nitriding include ammonia and nitrogen gas
  • nitrogen gas was used to avoid post nitriding mechanical steps that are required if one uses ammonia.
  • Use of ammonia while generating nitrogen atoms also generates hydrogen atoms that can react with the surface.
  • the surface 220 of the sample 200 undergoes hardening within the microwave plasma environment such that it exhibits an improved hardness (e.g., Rockwell Hardness HRC) without degrading other properties (e.g., strength) of the sample 200 being treated, and provides the treated sample 200 in a faster and more efficient manner.
  • the increase in surface hardness observed may depend on the concentration of the atomic species present to be diffused arid the temperature within the reactor. In the example of nitriding, increasing the nitrogen potential near the surface of the sample will increase the diffusion rate, and thus also the surface hardness.
  • the HRC of the sample may be increased to more than HRC 80 in under 10 minutes by increasing the nitrogen potential.
  • the furnace 100 of the embodiment shown in FIGS, 1 A-C, and the reactor 400 of the embodiment of FIGS. 2-4 provides a treatment area for the sample 200 therein for the surface treatment process, such as, for example, rapid nitridmg (and thus, furnace 100 and reactor 100 are interchangeably used as the furnace and reactor aspect are integrated in the furnace 100).
  • the reactor/furnace may have any suitable shape and size as based on the components used, so long as the components cooperate to provide an airtight space therein for controlling the oxygen content for processing the sample 200.
  • the reactor provides a treatment area for rapidly heating the plasma via a uniform microwave field (e.g,, based on a time-average distribution of microwaves) and processing the sample 200.
  • the microwaves enter the plasma processing cavity through ceramic insulation or components that are not at high temperature (as the insulation is not in contact with the plasma), as will be described in further detail below.
  • the rapid surface treatment process occurs within the reactor such that a diffusive species is formed using a gas as a source of the diffusion potential (e.g, nitrogen for a nitriding process),
  • a catalyst is also used in the reactor to generate plasma with the microwave radiation, however other ways of plasma generation is also contemplated, including, but not limited low pressure plasma generation or arc discharge, and discussion of a catalyst is not intended to be limiting.
  • nitriding may be referred to hereinafter as the diffusive species for the rapid surface treatment
  • diffusion is not limited to nitriding, and other diffusive species, such as carburizing, boronization, earbonitriding, and others are also contemplated, and the precursor gas supplied may vary according to the specific surface treatment desired.
  • the sample 200 may be any suitable material for rapid surface treatment, such as, but not limited to alloys, ceramics, composites, metals, etc.
  • a titanium alloy may be referred to hereinafter as the sample, other titanium alloys, other similar metals and alloys, as well as other suitable sample materials are contemplated, and reference to titanium or a specific titanium alloy is not intended to be limiting.
  • the sample 200 may be comprised of a titanium alloy such as Ti 6 Al 4 V, which undergoes nitriding in the reactor using nitrogen gas as source of nitrogen potential.
  • the reac tor may be used with any specific diffusive species and any material for sample 200 to achieve a desired surface treatment and species diffusion. Specifics of the systems and methods for rapid surface treatment of the sample 200 will now be described in detail.
  • the furnace 100 includes a housing 105 having a top portion 107 and a bottom portion 110, defined along a vertical axis Y.
  • the bottom portion 110 may be supported on legs 102, such that the bottom portion 1 10 is vertically raised with respect to a base surface (not shown).
  • the bottom portion 110 includes a first body component 111 and a second body component ! 12 connected to form the bottom portion 110 of the housing 105 with a bottom inner cavity 113 defined therein.
  • the body components 1 1 1, 1 12 may be formed of stainless steel, in certain embodiments, and may interchangeably be referred to as first and second stainless steel components 111, 112 respectively.
  • the components 111, 112 may be stainless steel, any suitable material is contemplated other than stainless steel, such as, but not limited to inconel, or other metal alloys with strength similar to that of stainless steel.
  • the bottom portion 110 may be formed of any suitable number of components, or be a single integrated structure, and depiction of two components is not intended to be limiting.
  • the first body component 111 and the second body component 112 may be joined in any suitable manner, including, but not limited to, welding.
  • the first body component 111 may have any suitable shape, such as, but not limited to, a cylindrical profile as shown in FIGS, 1A-C.
  • the second body component 112 may have any suitable shape such as, but not limited to, a tapered cylindrical shape with a reduced diameter at a top end (as based on vertical axis Y), to reduce the working volume of the plasma generated in the top portion 107.
  • the second body component 112 may be omitted such that the bottom portion 110 is one integrated piece, in another embodiment, may not be tapered, or, in yet another embodiment, be tapered such that the upper end is wider than the lower end of the second body component 112,
  • the bottom portion 110 includes a first solid plate 114 positioned on the legs 102, and defining the bottom end of the bottom inner cavity 113.
  • the first solid plate 114 may be any suitable material, such as, but not limited to, stainless steel
  • the first body component 111 is connected to the first solid plate 114 in any suitable manner, such as, for example, by welding.
  • the first solid plate 114 may include a flange for receiving the first body component 111 thereon.
  • the bottom portion 110 includes a seating ring 115 (e.g., an O-ring seal) including an radio frequency (RF) choke/gasket for sealing the connection between the first body component 1 11 and the first solid plate 114, thus providing a microwave seal and/or a vacuum seal between the components to prevent leaking from the inside cavities of the reactor.
  • RF radio frequency
  • the RF choke or gasket may be any suitable mechanical component, Including, but not limited to a steel mesh O-ring that is put inside a groove between flanges of the first and second body components 11 1, 1 12.
  • the first and second body components 111, 112 may also be joined together with bolts or clamps together for easy opening to access the bottom inner cavity 113.
  • thermocouple tubing 118 gas inlet aperture 116a, gas outlet aperture 117a, as well as a thermocouple aperture 118a, respectively.
  • Gas for generating the diffusive species is supplied to via the gas inlet 107 below the first solid plate 114 and into inlet tubing 116, extending through the first solid plate 114 via the inlet aperture 116a and upward to the top portion 107.
  • Gas from the top portion 107 is pumped out via outlet tubing 117, extending through the first, solid plate 1 14 via the outlet aperture 117a.
  • Outlet tubing 117 may also be used as a vacuum port for drawing air out of the top portion 107.
  • the inlet tubing 116, the outlet tubing 117, and the thermocouple tubing 118 may be any suitable material for supplying the gas for providing the potential to the top portion 107, including, but not limited to, titanium.
  • FIG. 1C the bottom surface of the first solid plate 1 14 is shown with the apertures 116a, 117a, 1 18a, and the inlet tubing 116, the outlet tubing 117, and the thermocouple tubing 118, Additional tubing may and apertures may be provided based on the desired gas flow' and vacuum desired for the furnace 100, and the depiction and positioning of the tubing is not intended to be limiting.
  • the top end of the bottom portion 110 is separated from the top portion 107 by a second solid plate 123.
  • the furnace 100 includes a ceramic plate 119 within the bottom inner cavity 1 13, towards the top portion 107,
  • the ceramic plate 119 may be any suitable material including, but not limited to silicon nitride, or yttria-stabi Sized zirconia.
  • the ceramic plate 1 19 may have any suitable thickness, for example, 0,20 in to 0,55 in.
  • the ceramic plate 119 may be positioned on a lip formed along the interior surface of the body component 112, and below the second solid plate 123, In another embodiment (not shown), the ceramic plate 119 and the second sohd plate 123 may be switched, such that the ceramic plate 119 is located horizontally above the second solid plate 123.
  • the ceramic plate 1 19 also includes corresponding apertures for receiving the inlet tubing 116, the outlet tubing 117, and the thermocouple tubing 118 therethrough,
  • the ceramic plate 119 allows microwaves to travel therethrough into the top portion 107 for heating the plasma for treating the surface 220 of the sample 107 positioned within the top portion 107,
  • the bottom inner cavity 113 of the bottom portion 1 10 is filled with ceramic insulation 120, with the ceramic insulation 120 surrounding the inlet tubing 1 16, the outlet tubing 117, and the thermocouple 118,
  • the bottom portion 110 may further include additional ceramic insulation 120 above the ceramic plate 119, on a side of the ceramic plate 119 towards the second solid plate 123.
  • the ceramic insulation 120 is included in the bottom portion 110 to prevent heat from escaping the top portion 107 and returning towards the first solid plate 114,
  • the ceramic insulation 119 may be any suitable thermal insulation and in any form, such as, but not limited to, flexible insulation,
  • the bottom portion 110 of the furnace 100 further includes magnetron ports 12la, 121 b defined as openings in the first body component 111.
  • the magnetron ports 121a, 12 lb allow for connecting the furnace 100 to respective magnetrons (not shown) for supplying microwaves to the furnace 100 such that the microwaves can travel to the top portion 107 for generating a uniform field (e.g,, based on the time-average microwaves within the top portion 107) for rapidly heating the plasma in the top portion 107 for evenly hardening the various external surfaces 220 of the sample 200,
  • the magnetrons may have any power capability based on the desired surface treatment and processing conditions for the particular sample being treated, and for the heating requirements for the particular metal, alloy, composite, ceramic, etc.
  • the magnetrons individually or in combination may deliver up to 6 kW @ 2.45 GHz.
  • the magnetrons may individually or collectively supply up to 500 kW at various GHz (e.g., up to 50 GHz), as based on the particular magnetrons supplied.
  • the delivery of kW at various GHz are contemplated across various embodiments because upon the plasma being generated and filling the plasma generation region 132, the microwave frequency is not constrained based on the process being carried out (e.g., carburization, nitriding, coatings, etc.).
  • any suitable microwave frequency can achieve the desired results, as similarly noted for the material nature of the sample being processed.
  • magnetron ports 121a, 121b, 121c are shown in FIG, 1 A, and two magnetron ports 121a, 121b are shown in the cross-sectional view of FIG. 1B, any number of magnetron ports is contemplated, and depictions of the magnetron ports 121a, 121b, 121c are not intended to be limiting.
  • the magnetron ports 121a, 121b, 121c are positioned in any suitable manner such that cross-talk between the magnetrons can be limited.
  • the magnetron ports may be asymmetrically positioned about the periphery of the bottom portion 110, such that no two magnetron ports are facing opposite each other (e.g., 180 degrees apart for a cylindrical housing 105), Moreover, in certain embodiments, the position height of each magnetron port may be the same along the vertical axis (as shown in FIG, 1A-B), or, in other embodiments, may be staggered at different heights to further reduce crossing between magnetrons. The number of magnetrons and associated magnetron ports may further depend on the power requirements of the application, and the present depiction of ports is not Intended to be limiting.
  • the top portion 107 includes a third body component 122, connected to the second solid plate 123, defining a top inner cavity 124 therein.
  • the second solid plate 123 separates the bottom inner cavity 113 of the bottom portion 110 from the top inner cavity 124 of the lop portion 107,
  • the third body component 122 may be any suitable material as previously discussed with reference to the first and second body components 111, 112.
  • each body component 111, 112, 122 may be the same material or a different material, based on the desired design of the furnace 100.
  • the second body component 112 of the bottom portion 110 may be connected to the second solid plate 123 in any suitable manner, such as by welding the second body component 112 to a flange on the second solid plate 123.
  • the second solid plate 123 includes apertures defined therethrough for receiving the inlet tubing 115, the outlet tubing 116, and the thermocouple tubing 117 therethrough.
  • the top portion 107 includes a sealing ring 125 (e.g, an O-ring seal) including an RF choke/gasket for sealing the connection between the third body component 122 and the second solid plate 123, and providing a vacuum and or microwave seal therebetween, similar io the sealing ring 115 previously described.
  • top inner cavity 124 is an airtight cavity for receiving the microwaves from the bottom portion 110 through the ceramic plate 119 and the second solid plate 123 such that plasma can be heated uniformly via the microwave field generated in the top inner cavity 124 to treat the sample 200
  • the components may be sealed mechanically andor with a suitable sealant, such as, but not limited to silicone RTV.
  • RTV sealant is replaced by other flexible sealant with low VOCs or selected based on the materials to be joined, in certain embodiments, as shown in FIGS. lA-B, the third body component 122 may be hemispherical at the top with an elongated cylindrical base.
  • other shapes are contemplated (e.g,, flat, square, rectangular, pyramidical, or other shape) based on the sample size and dimensions being processed.
  • the third body component 122 has an inner surface 122a on the side of the top inner cavity 124, and an outer surface 122b,
  • the inner surface 122a includes a high temperature ceramic liner to coniine heat in the top inner cavity 124 (and indirectly in the plasma generation region 132).
  • the high temperature ceramic liner is any suitable material that maintains its structural integrity in high temperature environments and has generally insulative properties, for example, in some embodiments, the high temperature ceramic brier is structurally stable up to TI50°C in some embodiments, and up to 1500°C in other embodiments.
  • the outer surface 122b may also include insulation thereon to limit heat loss from the top portion 107
  • the ceramic liner and or the insulation may be any suitable material, such as, but not limited to silicon nitride or other ceramic, and may be in any suitable form, such as flexibly thermal insulation, to limit heat loss from top portion 107.
  • the third body component 122 includes cooling coils 128 positioned about the periphery of the outer surface 122.
  • the cooling coils 128 may be positioned at any suitable height of the top portion, and depiction of the cooling coils 128 towards the second solid plate 123 is not intended to be limiting.
  • the cooling coils 128 may flow any suitable coolant, such as water, air, or a refrigerant, based on the cooling desired.
  • the top portion 107 further includes a mode mixer 129 at a top end of the top portion 107 within the top inner cavity 124.
  • the mode mixer 129 is attached and exposed to the top inner cavity 124 via the body component 122 such that it can uniformly distribute the microwave field inside the top inner cavity 124,
  • the top portion 107 also includes an optical pyrometer 130 towards a top end of the third body component 122 for remotely sensing the temperature of the surface 220 of the sample 200.
  • the top portion 107 may also include a pressure gauge for measuring the pressure within the top inner cavity 124.
  • a sample holder 126 is positioned within the top inner cavity
  • the sample holder 126 may be made of any suitable material having high temperature capability, high thermal shock resistance, low porosity, and capable of maintaining its structural integrity in a high temperature (e.g., up to 1150°C in some embodiments, and up to 1750°C in other embodiments). In one or more embodiments, the sample holder 126 may be comprised of silicon nitride, however other suitable materials are also contemplated.
  • the sample holder 126 is vertically spaced from the second solid plate 123 and positioned within the top inner cavity 124 to position the sample 200 for surface treatment. In the embodiment shown in FIGS. 1A-B, the sample holder 126 is a surface positioned on the thermocouple tubing 128.
  • the sample holder 126 is accessible via a loading door 127 defined in the third body component 122,
  • the loading door 127 may have any suitable size as based on the types of samples being processed within the furnace 100, and may include a window 127a therein for viewing the sample 200.
  • the window 127a may be any suitable material or size to maintain the plasma generation environment In the top inner cavity 124, such as, but not limited to, quartz.
  • An inner surface of the window 127a may also be coated with ceramic insulation.
  • a door 127 is shown, the entire third stainless steel component 122 may be removable by a lift hook (not shown) in another embodiment, and the sample 200 may be thus loaded in any suitable manner arid the presence of a door is optional .
  • the sample 200 (e.g., a titanium alloy such as, but not limited to a Ti 6 Al 4 V,) to be treated is placed on the sample holder 126 in the top inner cavity 124 via the loading door 127 (or in another suitable manner in other embodiments).
  • a catalyst (not shown) may also be placed on the sample holder 126 for interacting with the microwave field and generate plasma instantaneously.
  • the sample 200 is then covered by a ceramic cover 131 , within the top inner cavity 124, with the catalyst therein as well.
  • the ceramic cover 131 may be any suitable shape for covering the sample 200 and creating a plasma generation region 132 therein around the sample 200.
  • any suitable shape is contemplated for forming the plasma generation region 132, such as, but not limited to, a pyramidical, cylindrical rectangular, square, or other prismatic shape.
  • the ceramic cover 131 may be any suitable high temperature ceramic material, such as, but not limited to midlite, silicon nitride (e,g., Si 3 N 4 ), or other material having may have a low porosity, a high temperature capability, high thermal shock resistance, and low microwave absorption and formability.
  • the temperature capability may be, in some embodiments, up to 1 150 °C, and in other embodiments, up to 1750 °C,
  • Both the sample holder 126 and the ceramic cover 131 may be sized according to the sample 200 being treated, and different size domes can be used to accommodate larger size samples, and the depiction of the furnace 100 is not intended to be limiting or to scale.
  • the plasma is generated inside the ceramic cover 131 in the plasma generation region 132, thus confining the plasma around the sample 200 and not allowing plasma to form in the top inner cavity 124, Thus, energy is confined near the sampl e 200 in the plasma generation region 132, and not spreading throughout the volume of the top inner cavity 124.
  • the loading door 127 is closed and an inert gas (e.g., argon) is flowed through the top portion 107 to purge the air out of the top inner cavity 124 and the plasma generation region 132.
  • an inert gas e.g., argon
  • the magnetrons are turned on such that microwave power generates plasma instantaneously (e.g., in under 1 millisecond, in certain embodiments, in under 0.9 milliseconds in other embodiments, and in under 0.8 milliseconds in yet other embodiments) within the plasma generation region 132.
  • the temperature within the furnace 100, and within the plasma generation region 132 starts to rise rapidly (e.g., in some embodiments up to 1000°C/min, in other embodiments up to 1250°C/mm) after the initiation of the plasma.
  • the plasma is uniformly heated via the microwave field being uniform in the top inner cavity 124 by way of the mode mixer 129.
  • Direct current (DC) bias e.g., of 1 to 20 kV, in certain embodiments
  • the application of the DC bias to the sample 200 attracts positive ions in the plasma towards the sample 200, thus confining the generated plasma energy around the sample 200 in the plasma generation region 132.
  • the confined plasma generation limits the energy dissipation away from the sample 200 (e.g., toward the ceramic liner 122a of the third body component 122), thus improving energy efficiency of the furnace 100 and reducing the thermal load on the ceramic liner surface 122a of the third body component 122. Also, by attracting ions toward the sample 200. the processing uniformity is improved by concentrating and uniformly dissipating the ions into the surface of the sample 200.
  • the furnace 100 provides a system for rapidly and uniformly hardening the surface 220 of the sample 200, Via the uniform microwave field pro vided in the furnace 100. and the confinement of the plasma within the plasma generation region 132 via the ceramic cover 131 and the DC bias applied, the surface can be heated at rates up to 1 ,000°C minute, for example,, to efficiently and uniformly treat and harden the surface 220 of the sample 200.
  • U tilizing the furnace 100 based on atmospheric microwave plasma technology has certain advantages over conventional furnaces currently used in industry, including energy efficiency, ‘green ‘ processing, and versatility (i.e., the furnace 100 can be used both for rapid heating and for species generation in specific industrial applications).
  • higher numbers of species may be generated for diffusion or for coating deposition due to higher collision frequency among the molecules compared to radiofrequency or lower frequencies.
  • a system including a furnace 300 for receiving an atmospheric plasma reactor 400 therein is provided for treating the sample 200, according to another embodiment.
  • the furnace 300 includes a chamber housing 310 defining a chamber cavity 315 therein, and a door 320 for selectively opening (see FIG, 3) and closing the chamber cavity 315 to form a sealed microwave chamber, as in FIG. 2.
  • the chamber housing 310 may be any suitable material capable of withstanding the microwave energy within the chamber cavity 315.
  • the chamber cavity 315 defined in the chamber housing 310 may be any suitable size for receiving one or more reactors 400 therein.
  • the furnace 300 is shown as generally cylindrical in shape, any shape of the furnace 300 is contemplated, and the shape of the furnace 300 is not intended to be limiting.
  • the furnace 300 provides microwave chamber for heating the reactor 400, such that magnetrons (not shown) supply microwave radiation uniformly to the reactor 400 sealed in the chamber cavity 315.
  • the furnace 300 may, in certain embodiments, include a mode mixer for making the average microwave field generally uniform inside the chamber cavity 315, or may include any suitable mechanism to make the microwave field uniform for penetrating the insulation layers and housing structure of the reactor 400 for heating the plasma generated therein (as will be discussed with reference to FIG. 4).
  • the magnetrons of the furnace 300 may have any suitable rating based on the desired processing conditions for the particular sample being treated, and the beating requirements for the particular metal, alloy, composite, ceramic, etc. For example, the magnetrons may individually or in combination deliver up to 6 kW @ 2,45 GHz in nitriding applications for titanium alloys. For other sample types, other microwave frequencies may be used as desired for the particular sample being treated and the heating requirements for the particular metal or alloy.
  • Each magnetron may be able to individually or in combination deliver, in some embodiments, up to 500 kW, as based on the particular magnetrons supplied.
  • the delivery of kWs at various GHz are contemplated across various embodiments because upon the plasma being generated and filling the reactor 400, the microwave frequency is not constrained based on the process being carried out (e.g., carburization, nitriding, coatings, etc,).
  • any suitable microwave frequency can achieve the desired results, as similarly' noted for the material nature of the sample being processed.
  • the reactor 400 When positioned in the furnace 300 for treatment of the sample 200, the reactor 400 is connected through ports in the door 320, such that tire reactor 400 can be evacuated by a vacuum pump connected to a gas outlet in the reactor 400. Furthermore, the reactor 400 can be filled with an inert gas, such as for example, argon, at atmospheric pressure.
  • an inert gas such as for example, argon
  • nitrogen gas, and, in certain embodiments, ammonia (and optionally argon or another inert gas) are fed through the ports in the door 320 to the reactor 400.
  • the gas flow rates ami the pumping speed may be controlled by valves and the pressure may be measured by a gauge connected to the gas lines,
  • the reactor 400 includes a plurality of nested body components 410, 420, 430, with the innermost component 430 defining an inner cavity 440 therein.
  • Each body component 410, 420, 430 is connected to and sealed at a base 405, forming the bottom of the inner cavity 440 and the support for the reactor 400, As dependent on the shape of the body components, the body components 410, 420,
  • the body components may be any suitable housing for forming an inner cavity 440 for treatment of the sample 200 therein.
  • each inner body component has a diameter and height less than that of the adjacent outer component (and any additional concentric component positioned radially outward thereof.
  • the body components 410, 420, 430 may have any suitable size for forming the inner cavity 440 for treating the sample 200, For example, in some embodiments each of the body components has a diameter at a base defining an opening of 1 to 20 inches, in other embodiments, 2 to 15 inches, and in yet other embodiments 3 to 10 inches.
  • any suitable number of body components may be layered to provide sufficient thermal insulation between the inner cavity 440 and the outermost body component 410.
  • the nested body components 410, 420, 430 include thermal insulation 450 (e.g., flexible ceramic insulation), therebetween to reduce heat loss from the inner cavity 440 to the chamber cavity 315.
  • thermal insulation 450 e.g., flexible ceramic insulation
  • a similar thermal insulation such as the flexible ceramic material, may be used to pack a top portion of the inside of the cavity within the innermost body component 430.
  • an insulative material of higher insulalive value may be used to reduce the number of body components or amount of insulation required, or less insulative value may be used with additional body components.
  • the body components themselves provide some insulation via their material construction.
  • the material of the body components 410, 420, 430 may be any suitable material, such as but not limited to quartz.
  • the system provided by the nested body components arid insulation layers is configured to maintain the temperature inside the inner cavity 440 at the desired temperature (in some instances up to 1750 °C), arid allow microwave penetration therethrough for heating the plasma in the inner cavity 440 for treating the sample 300.
  • Sealant used for sealing the body components 410, 420, 430 and the base 405 may be any suitable sealant as previously discussed, and the insulative properties of the insulation and the body components allows the temperature at the outermost body component to be below the level at which the sealant would fail (for the RTV sealant, at most 150°C),
  • the inner cavity 440 includes a stack of ceramic discs 450 therein.
  • the stack of ceramic discs 450 forms a sample holding surface 452 for receiving the sample
  • the discs 450 may be integrated into a single ceramic slab, or many include any number of discs 450.
  • the stack of ceramic discs 450 may be any suitable material having high temperature stability (e.g., up to 1750 o C), high thermal shock resistance, and low porosity, as similarly discussed for the sample holder in furnace 100, such as, but not limited to, mullite or silicon nitride (e.g., Si 3 N 4 ),
  • the sample 200 is then then covered with a ceramic cover 460, placed on the stack of ceramic discs 450.
  • the ceramic cover 460 is similar to the ceramic cover 131 of furnace 100, and forms a plasma generation region 462 around the sample 200 to confine the plasma around the sample 200 and prevent the generated plasma from dissipating into the inner cavity 440.
  • the ceramic cover 460 may be any suitable material as previously discussed for ceramic cover 131, including, but not limited to, mullite, silicon nitride (e,g Stephen Si 3 N 4 ), or other suitable high temperature ceramic material (c.g., capability up to 1750°C).
  • the ceramic cover 460 may have any suitable dimensions for covering the sample 200.
  • the cover has a diameter of 1 to 5 inches, in other embodiments, 2 to 4 inches, and in yet another embodiment a diameter of 3.5 inches, in certain embodiments, the cover has a height: of 1 to 5 inches, in other embodiments, 2 to 4 inches, and in yet another embodiment 3 inches,
  • inner cavity 440 may also be filled with flexible ceramic insulation to prevent formation of plasma in the inner cavity 440.
  • the reactor 400 includes inlet tubing 470 and outlet tubing 475 for gases extending through the stack of ceramic discs 450 and the base plate 405 to provide gas to the inner cavity 440, and more particularly, to the plasma generation region 462.
  • the tubing may be any suitable material, such as, but not limited to, a titanium alloy.
  • the inlet tubing 470 and outlet tubing 475 may be connected to the door 320 of the furnace 300 when placed within the furnace 300 such that the gas can be supplied to the reactor 400 and/or the reactor 400 can be vacated via a vacuum pump.
  • the reactor 400 also includes a thermocouple feedthrough 480, similar to the thermocouple tubing 118 described for the furnace 100, which provides a DC bias to the plasma generation region 462 to attract ions to the surface 220 of the sample 200, as similarly described above.
  • the magnetrons can generate a microwave Held uniformly surrounding the reactor 400 such that plasma is instantaneously generated within the plasma generation region 462, and rapidly heated to treat the surface 220 of the sample.
  • the speed of plasma generation and heating is similar to that provided for furnace 100, and the reactors 100, 400 provide different apparatuses for conducting the surface treatment of the sample, with the furnace 100 being directly connectable to the magnetron sources versus the reactor 400 being housed within a furnace for generating the microwave field for heating.
  • the furnace 100 and reactor 400 may have any suitable size based on the samples 200 to be processed.
  • the reactors may be any suitable size (i.eerne have a diameter or overall height) based on the process requirements and/or the sample 200 being treated.
  • the ratio of the top portion 107 and the bottom portion 110 are not fixed in scale and may be altered based on the process requirements arid temperature requirements of the plasma generation.
  • the body components may be sized per the desired cavities based on the size of the sample 200, In certain examples, the each body component may have a diameter of 4 to 20 inches, in other embodiments, 5 to 15 inches, and in yet other embodiments 6 to 10 inches. In some embodiments, the overall height of the furnace 100 may be 5 to 25 inches, in other embodiments, 8 to 20 inches, and in yet other embodiments 10 to 18 inches.
  • the additional body components may be sized per the outermost body component (as based on the furnace) or per the innermost body component (as based on forming the cavity for receiving the sample).
  • the top portion 107 of the furnace 100 may have a diameter of 7.5 inches and an overall height of 12 inches.
  • the diameter, length and shapes of first, second, and third body components of furnace 100 are not fixed and may depend upon the sample and the processing requirements for the sample. In one embodiment: these parts can have diameters of 4 to 8 inches and lengths of 4 to 12 inches. In another embodiment these parts can have diameters of 6 to 12 inches and lengths of 8 to 20 inches, and in yet another embodiment the diameters can be 12 to 48 inches and lengths 15 to 60 inches. It may be pointed out that the size and shapes can vary widely depending upon the sample size, number of samples processed together, and the process itself.
  • a method 500 of surface treatment of sample includes, at step 510, placing a sample to be treated and a catalyst on the sample holder inside the processing cavity of an atmospheric microwave plasma reactor.
  • a catalyst is described herein, other methods for generating plasma are also contemplated, and the use of a catalyst is not intended to be limiting.
  • the plasma may be started at low pressure or beformed via arc discharge.
  • the sample and catalyst are covered by a ceramic cover and the cavity is sealed and purged.
  • Air is purged from the cavity at step 520 by either displacing the air inside the cavity by flowing an inert gas (e.g., argon for about 1 to 5 minutes, in some embodiments, oy by using a vacuum pump to evacuate the cavity).
  • an inert gas e.g., argon for about 1 to 5 minutes, in some embodiments, oy by using a vacuum pump to evacuate the cavity.
  • microwave power is turned on to form a uniform microwave field within the reactor, thus generating plasma instantaneously via interaction between the catalyst and the microwave radiation, and uniformly filling the plasma generation region around the sample.
  • the plasma may be generated in under 1,5 milliseconds in some embodiments, under 1.25 milliseconds in other embodiments, and under 1 millisecond in yet further embodiments.
  • the plasma is then heated via the microwave field applied.
  • the beating of the plasma within the plasma generation region may be at any suitable rate determined by the amount of microwave power applied.
  • the heating rate may be up to 1,000 o C/mlmite, in other embodiments up to 750°C/minute, and in yet other embodiments, up to 500°C/minuie.
  • Other heating rates are also contemplated, such as higher rates based on higher power microwaves, in an embodiment, for example, a 300°C/minute heating rate may be observed for 2,3 kW of power.
  • the temperature is monitored by a thermocouple via thermocouple tubing described for the reactors 100, 400.
  • the thermocouple may be any suitable thermocouple, such as but not limited to an S-type thermocouple,
  • step 540 During the heating of step 540, the temperature rises rapidly after the initiation of the plasma based on the heating rate as determined by the microwave power applied.
  • DC bias is applied.
  • the DC bias is applied, in one or more embodiments, as the temperature of the sample is rising.
  • the DC bias may be, in some embodiments, 1 to 20 kV, in other embodiments, 1.5 to 18 kV, and in yet other embodiments, 2 to 15 kV.
  • the sample is treated for a duration based on the desired surface hardening for the sample.
  • the processing time may be a few' minutes, e.g., up to 10 minutes in certain embodiments, up to 5 minutes in other embodiments, and up to 3 minutes in yet other embodiments.
  • the sample may optionally be gas quenched inside the reactor.
  • the presently described microwave plasma system provides rapid and uniform beat generation and a confined plasma generation region near the surface of the sample for surface treatment via atmospheric microwave plasma in an energy efficient system.
  • a nitriding experiment was conducted using the system for atmospheric plasma surface treatment of the above disclosure.
  • a cylindrical block of titanium alloy (sample), Ti 6 Al 4 V grade 5 of dimensions 1 inch OD and 1 inch length was placed on the sample holder along with a catalyst.
  • the sample was then covered with a mullite dome followed by sliding of the set of quartz cylinders over the sides of the discs.
  • the stainless steel ring was then bolted to the base plate to seal the cavity within the set of quartz cylinders.
  • the system consisting of the quartz cylinders and their interior, was evacuated to mTorr range via a vacuum pump. Argon gas was used to backfill the system and the pump was turned off. The pressure was brought to atmospheric pressure with argon gas. The microwave power of about 23 kW was then turned on. The temperature is monitored by an S type thermocouple whose tip is very close to foe base of the titanium alloy sample. Within five minutes and with this microwave power, the surface temperature of about 1500 °C was observed on the sample. Nitrogen gas was then introduced in the system for another five minutes for nitriding foe sample. The system was then allowed to cool down to room temperature.
  • the plasma was started at lower pressures, in mTorr range, and then pressure was increased to atmospheric pressure. The temperature approached to around 1500°C in about 5 minutes and then nitrogen gas was introduced for another five minutes. After allowing foe sample to cool down, sthe ante surface hardness number was observed.
  • the system was evacuated to mTorr range pressure and then argon was introduced. The pressure was maintained in mTorr range as the sample was heated at low pressures. With slightly higher microwave power, the surface temperature of the sample was again observed to reach about 1500°C in five minutes. Nitrogen gas was introduced as before in the system for another five minutes. The system was allowed to cool down and then surface hardness was measured. It was measured to be HRC 62.

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Abstract

Un procédé de traitement de surface d'un échantillon consiste à placer un échantillon sur un porte-échantillon d'un réacteur à plasma par micro-ondes comprenant un logement de réacteur délimitant une cavité interne en son sein, à couvrir l'échantillon avec un couvercle en céramique pour créer une région de génération de plasma autour de l'échantillon et à évacuer la cavité interne et la région de génération de plasma par l'intermédiaire d'un tube de sortie s'étendant depuis l'extérieur du logement vers la région de génération de plasma. Le procédé consiste en outre à laisser s'écouler un gaz de traitement vers la région de génération de plasma par l'intermédiaire d'un tube d'entrée depuis l'extérieur du logement vers la région de génération de plasma pour créer un potentiel, à activer une énergie micro-onde pour générer un champ de micro-ondes uniforme autour de la région de génération de plasma et générer un plasma à l'intérieur de la région de génération de plasma, et à chauffer le plasma par l'intermédiaire du champ de micro-ondes pour traiter la surface de l'échantillon.
PCT/US2021/014092 2020-01-20 2021-01-20 Processus et systèmes pour un traitement de surface rapide WO2021150549A1 (fr)

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Citations (7)

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US5276386A (en) * 1991-03-06 1994-01-04 Hitachi, Ltd. Microwave plasma generating method and apparatus
US5712000A (en) * 1995-10-12 1998-01-27 Hughes Aircraft Company Large-scale, low pressure plasma-ion deposition of diamondlike carbon films
US20040089631A1 (en) * 2002-11-12 2004-05-13 Blalock Guy T. Method of exposing a substrate to a surface microwave plasma, etching method, deposition method, surface microwave plasma generating apparatus, semiconductor substrate etching apparatus, semiconductor substrate deposition apparatus, and microwave plasma generating antenna assembly
US20060040064A1 (en) * 2004-06-08 2006-02-23 Marik Dombsky Method of forming composite ceramic targets
US20060162818A1 (en) * 2002-05-08 2006-07-27 Devendra Kumar Plasma-assisted nitrogen surface-treatment
US20060237398A1 (en) * 2002-05-08 2006-10-26 Dougherty Mike L Sr Plasma-assisted processing in a manufacturing line
US20120086464A1 (en) * 2010-10-12 2012-04-12 Applied Materials, Inc. In-situ vhf voltage/current sensors for a plasma reactor

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5276386A (en) * 1991-03-06 1994-01-04 Hitachi, Ltd. Microwave plasma generating method and apparatus
US5712000A (en) * 1995-10-12 1998-01-27 Hughes Aircraft Company Large-scale, low pressure plasma-ion deposition of diamondlike carbon films
US20060162818A1 (en) * 2002-05-08 2006-07-27 Devendra Kumar Plasma-assisted nitrogen surface-treatment
US20060237398A1 (en) * 2002-05-08 2006-10-26 Dougherty Mike L Sr Plasma-assisted processing in a manufacturing line
US20040089631A1 (en) * 2002-11-12 2004-05-13 Blalock Guy T. Method of exposing a substrate to a surface microwave plasma, etching method, deposition method, surface microwave plasma generating apparatus, semiconductor substrate etching apparatus, semiconductor substrate deposition apparatus, and microwave plasma generating antenna assembly
US20060040064A1 (en) * 2004-06-08 2006-02-23 Marik Dombsky Method of forming composite ceramic targets
US20120086464A1 (en) * 2010-10-12 2012-04-12 Applied Materials, Inc. In-situ vhf voltage/current sensors for a plasma reactor

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