EP1172455A2 - Oberflächenbehandlungsverfahren von Titan - Google Patents

Oberflächenbehandlungsverfahren von Titan Download PDF

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Publication number
EP1172455A2
EP1172455A2 EP01117022A EP01117022A EP1172455A2 EP 1172455 A2 EP1172455 A2 EP 1172455A2 EP 01117022 A EP01117022 A EP 01117022A EP 01117022 A EP01117022 A EP 01117022A EP 1172455 A2 EP1172455 A2 EP 1172455A2
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EP
European Patent Office
Prior art keywords
carburizing
titanium metal
gas
temperature
carbon
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01117022A
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English (en)
French (fr)
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EP1172455A3 (de
Inventor
Eiichi Ishii
Takumi Sone
Yukihiro Sato
Kei Demizu
Hideo Kakutani
Koichi Tanaka
Shinichi Tanaka
Noriyoshi Tsuji
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Osaka Municipal Government
Tanaka Ltd
SDC Inc
Original Assignee
Osaka Municipal Government
Tanaka Ltd
SDC Inc
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Filing date
Publication date
Application filed by Osaka Municipal Government, Tanaka Ltd, SDC Inc filed Critical Osaka Municipal Government
Publication of EP1172455A2 publication Critical patent/EP1172455A2/de
Publication of EP1172455A3 publication Critical patent/EP1172455A3/de
Withdrawn legal-status Critical Current

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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
    • 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

Definitions

  • This invention relates to a method of surface treatment of titanium metal.
  • titanium metal is heat-resistant and is substantially equal in strength to carbon steel. Also, it is known to have a good corrosion resistance because it forms an oxide film on its surface.
  • pure titanium it is possible to improve its workability and mechanical strength by forming an alloy with any metal, especially copper, tin, iron, aluminum, vanadium, chrome, cobalt, molybdenum, tungsten, etc.
  • cleaning treatment is carried out in which deposits on the surface of the titanium metal are spattered by turning a mixture of hydrogen gas and argon gas into plasma.
  • Such cleaning treatment for a titanium metal is carried out at a high temperature of 700 °C or over in the same manner as in carburizing treatment. This is because at a temperature below 700 °C , the surface would not be activated or infiltration of activated carbon would not be achieved sufficiently.
  • solution treatment is often carried out with a titanium alloy as a matrix and thereafter aging treatment at about 500-700 °C is carried out for precipitation hardening.
  • aging treatment at about 500-700 °C is carried out for precipitation hardening.
  • a surface layer is formed which comprises a phase in which ⁇ -type (hexagonal system) and ⁇ -type (body-centered cubic system) structures are present in a mixed state. This causes not only the ⁇ type but ⁇ type structure to deposit on the surface of the titanium alloy, so that the effect of precipitation hardening of the ⁇ type by aging treatment lowers.
  • An object of this invention is to carburize titanium metal so that the strength inherent to a titanium metal is maintained and excellent wear resistance and low friction coefficient and improved corrosion resistance are achieved.
  • Another object is to provide a carburizing treatment method in which when carburizing is carried out at a low temperature, carbon reliably infiltrates into between metallic atoms without turning to amorphous and depositing on the metal surface even at a lower temperature than 700 °C.
  • a method of surface treatment of titanium metal wherein plasma carburizing is carried out in an atmosphere comprising a carburizing gas having the molar ratio of hydrogen atoms (H) to carbon atoms (C) adjusted to (H/C) ⁇ 9 at a pressure of 13-400 Pa and a temperature of 400-690 °C.
  • titanium metal can be carburized from the surface to a depth exceeding 50 ⁇ m under a low pressure of 13 to 400 Pa and at a low temperature of 400 to 690 °C.
  • activated carbon ions infiltrate into the crystal lattice of the metal, metal atoms flying out of the metal surface bind to the activated carbon ions and are covering the metal surface and diffuse into the interior of the metal, or carbon ions accelerated near the cathode are directly driven into the metal, so that a carburized layer comprising a carbonized metal layer is formed on the surface layer of the titanium metal.
  • plasma carburizing is carried out at a low temperature of 690 °C or lower, it is considered that as in aging treatment, an ⁇ -layer deposits on the surface of the titanium metal in which ⁇ -type (hexagonal system) and ⁇ -type (regular system) structures coexist, so that it is possible to turn many carbon atoms to solid solution on the surface to the limit of the ⁇ -type titanium metal at the predetermined temperature of plasma carburizing.
  • a method of surface treatment of a titanium metal which comprises the steps of heating the titanium metal to a temperature of 400-690 °C in a cleaning gas atmosphere containing hydrogen gas, subjecting the surface of the titanium metal to cleaning by applying a DC voltage of 200-1500 V, and plasma carburizing in an atmosphere comprising a carburizing gas having the molar ratio of hydrogen atoms (H) to carbon atoms (C) adjusted to (H/C) ⁇ 9 at a pressure of 13-400 Pa and a temperature of 400-690 °C.
  • a carburized layer comprising a carbonized metal layer will not deposit on the surface subjected to cleaning even at a low temperature, but carbon reliably penetrates into the crystal lattice to form a carburized layer.
  • the titanium metal referred to in this invention may be pure titanium or alloy of titanium and other metal component, and the composition of alloy is not particularly limited.
  • the purity of titanium of titanium metal as an industrial material is about 99.9 to 99.5% and such pure titanium may be used.
  • titanium alloy for example, copper, tin, iron, aluminum, vanadium, chrome, cobalt, molybdenum, tungsten, etc. may be used.
  • a hydrocarbon-family gas used for carburizing treatment is a general term for gases consisting of only carbon and hydrogen and hydrocarbon may be either chain hydrocarbon or cyclic hydrocarbon.
  • chain hydrocarbons paraffinic hydrocarbons shown by formula C n H 2n+2 , olefinic hydrocarbons (C n H 2n ), acetylenic hydrocarbons (C n H 2n-2 ) can be cited, and they may be straight-chain or have side chains.
  • methane, ethane, propane and butane are preferable, which are gases at normal temperature and need no vaporizing facility for use.
  • cyclic hydrocarbons they may be aromatic compounds or cycloaliphatic compounds. A representative example of aromatic compounds is benzene (C 6 H 6 ).
  • the molar ratio of hydrogen atoms (H) to carbon atoms (C) in the carburizing gas among the above plasma carburizing conditions should be (H/C) ⁇ 9. If the (H/C) ratio exceeds 9, carburization will not proceed smoothly, so that high-hardness state will not be attained by carburizing from the titanium metal surface to the depth of 50 ⁇ m, but the carbon becomes amorphous and deposits on the titanium metal surface.
  • the pressure of the carburizing gas should be 13 to 400 Pa.
  • Such a carburizing gas pressure is required to form a treated layer comprising mainly TiC on the surface layer of the titanium metal under low-pressure, low-current-density, high-voltage conditions.
  • the carbon content in the treated layer would be low, so that the sliding properties would not be sufficiently improved.
  • the carbon content in the carburized layer would reach a saturated value, so that the carburizing effect would not improve any further.
  • the plasma carburization according to this invention can be carried out in the following manner using a known carburizing apparatus (made by NDK Incorporated).
  • an article formed of a titanium metal is put in a treating chamber. After exhausting, it is heated to a temperature of 400-690 °C by a heater, nitrogen gas containing hydrogen gas is introduced and the article is held at the temperature for 10-60 minutes. Simultaneously, cleaning treatment is carried out to remove an oxide film formed on the surface of the titanium metal by applying a high DC voltage of 200-1500 V.
  • a carburizing gas comprising a hydrocarbon gas, hydrogen gas, etc. and having the molar ratio (H/C) of hydrogen atoms (H) to carbon atoms (C) adjusted to (H/C) ⁇ 9 is introduced into the furnace so that the pressure will be within the range of 13-400 Pa.
  • a high DC voltage of 400-600 V is applied at a current density of 0.1 A/m 2 -5 A/m 2 for plasma carburizing.
  • ionized activated carbon C+ will be produced, which adheres to the metal surface and further diffuses into the interior, or by the action of sputtering or implantation, carburizing reaction proceeds.
  • the atmospheric temperature for the plasma carburizing in this invention should be 400-690 °C. If lower than 400 °C, no matter how the current, voltage and carburizing gas pressure are adjusted, activated carbon could not penetrate into the titanium metal or diffuse therein. Also, if higher than 690 °C limit, the strength of the titanium metal might decrease.
  • a carburized layer as thick as e.g. 20 ⁇ m or over on the metal surface. Because no clear boundary is formed against the non-carburized portion of the metal, it is possible to form a less peelable and durable surface treated layer and thus to increase the lubricity and to reduce the friction coefficient by carbides and improve the wear resistance and corrosion resistance of the metal.
  • the treated layer on the titanium metal surface it is considered that by being carbonized, its carbide exhibits lubricity. This reduces friction coefficient and wear amount. But, it will not lower the corrosion resistance of the titanium metal. Also, because the treated layer can be formed into a relatively thick layer of e.g. about 70 ⁇ m, it is possible to form a durable surface treated layer.
  • a plurality of test pieces subjected to solution treatment in which after held for one hour at 950 °C, they were water-cooled
  • test pieces subjected to solution treatment and aging treatment in which after held for four hours at 540 °C, they were air-cooled to room temperature
  • STA test pieces subjected to solution treatment and aging treatment
  • a carburizing apparatus made by NDK Incorporated
  • a carburizing apparatus which had a treating chamber surrounded by a heat-insulating material such as graphite fiber in a heating furnace. While heating the interior of the treating chamber by use of heating elements made from a rod graphite, a DC glow discharge anode was connected to an upper portion of the treating chamber with a cathode connected to a table on which the articles to be treated were placed, and gas manifolds were provided at predetermined positions in the treating chamber so that process gases can be introduced by suitably changing over.
  • cleaning treatment was carried out at the cleaning temperatures and under other predetermined conditions shown in Table 1.
  • the treating chamber was exhausted and heated by a heater to the predetermined cleaning temperatures shown in Table 1, argon gas and hydrogen gas were introduced at predetermined flow rates under predetermined gas pressures, and the specimens were held at predetermined current and voltage values for predetermined time to clean the titanium metal surface.
  • plasma carburizing treatment was carried out at the carburizing temperatures and under other predetermined conditions shown in Table 2, and after treatment, nitrogen gas was pressed into the treating chamber and each specimen was cooled to room temperature.
  • ST and STA of Comparative Examples 2 and 3 were titanium metals treated by a carburizing gas in which the (H/C) ratio was 12, which exceeded 9, and both had a surface hardness (Hv) of less than 400. Thus, it is considered that hardening due to carburization did not occur.
  • titanium metal can be subjected to plasma carburizing from the surface to a depth exceeding 50 ⁇ m at a low pressure of 26-400 Pa in a low-temperature atmosphere of 400-690 °C . Also, as a result, the corrosion resistance of the titanium metal will not deteriorate, so that a relatively thick, durable sliding treated surface can be formed on its surface. Thus, it is possible to reduce the friction coefficient and wear amount in a stable state.
  • the titanium metal is subjected to plasma carburizing at predetermined pressure and temperature, it is possible to form a relatively thick, durable sliding treated surface on its surface without deteriorating the corrosion resistance of the titanium metal.
  • the friction coefficient and wear amount can be reduced in a stable state.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
EP01117022A 2000-07-12 2001-07-12 Oberflächenbehandlungsverfahren von Titan Withdrawn EP1172455A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2000211518 2000-07-12
JP2000211518 2000-07-12

Publications (2)

Publication Number Publication Date
EP1172455A2 true EP1172455A2 (de) 2002-01-16
EP1172455A3 EP1172455A3 (de) 2003-11-05

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EP01117022A Withdrawn EP1172455A3 (de) 2000-07-12 2001-07-12 Oberflächenbehandlungsverfahren von Titan

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US (1) US20020020476A1 (de)
EP (1) EP1172455A3 (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5211503B2 (ja) * 2007-02-16 2013-06-12 富士通セミコンダクター株式会社 半導体装置の製造方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2630133B1 (fr) * 1988-04-18 1993-09-24 Siderurgie Fse Inst Rech Procede pour l'amelioration de la resistance a la corrosion de materiaux metalliques
GB2261227B (en) * 1991-11-08 1995-01-11 Univ Hull Surface treatment of metals
JP2909361B2 (ja) * 1993-09-21 1999-06-23 大阪府 チタン金属の表面処理方法
AU1745695A (en) * 1994-06-03 1996-01-04 Materials Research Corporation A method of nitridization of titanium thin films
AU6784798A (en) * 1997-03-27 1998-10-20 Micron Technology, Inc. Titanium metal treatment method, method of forming an electrically conductive interconnect, and method of reducing contact resistance of an elemental titanium contact

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US20020020476A1 (en) 2002-02-21
EP1172455A3 (de) 2003-11-05

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