EP0122529B1 - A method for surface hardening a ferrous-alloy article and the resulting product - Google Patents

A method for surface hardening a ferrous-alloy article and the resulting product Download PDF

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Publication number
EP0122529B1
EP0122529B1 EP19840103561 EP84103561A EP0122529B1 EP 0122529 B1 EP0122529 B1 EP 0122529B1 EP 19840103561 EP19840103561 EP 19840103561 EP 84103561 A EP84103561 A EP 84103561A EP 0122529 B1 EP0122529 B1 EP 0122529B1
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EP
European Patent Office
Prior art keywords
set forth
article
nitriding
thermal diffusion
layer
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.)
Expired
Application number
EP19840103561
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German (de)
English (en)
French (fr)
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EP0122529A1 (en
Inventor
Tohru Arai
Junji Endo
Yoshihiko Sugimoto
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Toyota Central R&D Labs Inc
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Toyota Central R&D Labs Inc
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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
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/02—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
    • C23C12/00—Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material 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
    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D

Definitions

  • This invention relates to a method for surface hardening a ferrous alloy article which forms a carbonitride layer, particularly a layer of carbonitride of at least one element selected from V, Nb, Ta, on the surface of the article and to the ferrous alloy article obtained thereby.
  • the inventors of this invention have previously developed a method for surface hardening of a ferrous alloy article containing at least 0.2% by weight of carbon.
  • a layer of carbide of an element selected from V, Nb and Ta is formed on the article surface by treatment thereof with, for example, a molten salt, powder or gas containing this element.
  • This method described in DE-A-2 829 976 is widely used to prolong the life of, for example, a tool or mold.
  • the carbide layer is formed by thermal diffusion and combination of vanadium, niobium or tantalum, and carbon in the ferrous allow article.
  • the amount of carbon in the article immediately below the carbide layer is reduced as it is consumed for the formation of the carbide layer.
  • the article is hardened, its portion immediately below the carbide layer is likely to obtain a lower degree of hardness than the inner portion of the article. If this article is used for an application in which it is subjected to a high stress, it is likely that the portion immediately below the carbide layer may be deformed to cause the cracking or peeling of the carbide layer.
  • the prior method for surface treatment reduces the amount of carbon throughout the article and thereby makes it difficult to harden the article satisfactorily.
  • a layer of a carbide containing nitrogen or a carbonitride has recently been found to be higher in toughness than a carbide layer and has come to replace the carbide layer for the purpose of coating the surface of an article.
  • This carbonitride coating treatment is presently carried out by a method employing a gas, such as titanium tetrachloride. This method not only requires substantial caution for protecting the health of workers, but also is complicated and necessitates expensive equipment.
  • An object of this invention is to improve a previously-developed method for a carbide layer and provide a method which effectively forms (on the surface of a ferrous-alloy article) a surface layer composed of the carbonitride of at least one element selected from V, Nb, Ta and an inner layer composed of a ferrous alloy containing a solid solution of nitrogen.
  • Another object of this invention is to provide a method which easily and quickly forms a carbonitride layer.
  • a further object of this invention is to provide a ferrous alloy article which can be satisfactorily hardened.
  • This invention is applicable to a ferrous alloy article containing at least 0.2% by weight of carbon.
  • the presence of at least 0.2% by weight of carbon in the ferrous alloy is essential to form a carbonitride layer of good quality.
  • a ferrous alloy article contains less than 0.2% by weight of carbon, it is carburized before, during or after nitriding so that its surface portion may contain at least 0.2% by weight of carbon prior to its treatment for the formation of a nitrocarbide thereon.
  • the ferrous alloy article produced by the method of this invention has (on its surface) a surface layer composed of the carbonitride of an element selected from V, Nb, Ta and an inner layer composed of a ferrous alloy containing a solid solution of nitrogen immediately below the surface layer of the article, and can be hardened and quenched satisfactorily.
  • the surface hardening treatment of this invention includes nitriding. It is possible to employ any method, such as gas nitriding, gas soft nitriding, salt bath soft nitriding or glow discharge nitriding. Each of these methods is conventional and well known. It is preferable to form a nitrided layer having a high nitrogen content and a large depth. In the event carburization treatment follows nitriding, it is particularly important to form a nitrided layer having a sufficiently large depth and a sufficiently high nitrogen content, since diffusion of nitrogen into the inner or center portion of an article during carburization leads to a reduction in the amount of nitrogen in its surface portion. The carburization must be effected in a short time. Such carburization is well known and is readily effected by any skilled artisan.
  • the formation of a carbonitride layer can be effected by various processes, including molten salt dipping, molten salt electrolysis, powder packing, slurry process and fluidized furnace process. These processes and required compositions are, per se, known, but not in the context of the present invention.
  • This treatment combines an element selected from V, Nb and Ta in a treating agent and the carbon and nitrogen in the ferrous alloy article. This treatment is carried out at a temperature of at least about 600°C and lower than the melting point of the material to be treated. An appropriate temperature range is from 800°C to 1200°C. The period of time required for the treatment is in the range of from 30 minutes to 24 hours. When an electrolysis process is employed, it is appropriate to apply a cathode current density of from 0.01 to 3 A/cm 2 .
  • the treatment provides a surface layer having an increased thickness when the temperature and period of time are increased.
  • An increase in the thickness of the layer tends to develop fine pores in the layer and to lower its pitting and wear resistance.
  • the critical thickness beyond which those defects are intolerable depends on the element (V, Nb, Ta) employed, nitriding conditions, the kind of ferrous alloy article and treatment conditions for the carbonitride layer, there is usually no appreciable problem when the thickness does not exceed 10 11 m.
  • the treatment of this invention forms on the surface of a ferrous alloy article a surface layer composed of said carbonitride; the surface layer is outstanding in wear resistance and toughness.
  • the formation of the layer according to this invention is effected by the combination of not only carbon, but also nitrogen, in the article with the element selected from V, Nb and Ta, it obtains a predetermined thickness within a shorter period of time than a carbide layer does.
  • the treatment of this invention also forms a ferrous alloy layer containing a solid solution of nitrogen immediately below the carbonitride layer. This makes it possible to obtain a sufficiently high degree of hardness in the area immediately below the surface layer. Therefore, it is possible to harden the article satisfactorily, even when the article has only a small thickness.
  • the nitrided sample was prepared by two hours of immersion in a salt bath containing cyanide and having a temperature of 560°C. These samples were subjected to molten salt dipping, i.e. immersed in a bath of molten borax containing 20% by weight of vanadium oxide (V 2 0 5 ) and 10% by weight of boron carbide (B 4 C) and having a temperature of 1000°C for from 30 minutes to 16 hours, and oil quenched.
  • molten salt dipping i.e. immersed in a bath of molten borax containing 20% by weight of vanadium oxide (V 2 0 5 ) and 10% by weight of boron carbide (B 4 C) and having a temperature of 1000°C for from 30 minutes
  • a nitrided sample and an unnitrided sample were prepared from carbon steel for machine structural use, AISI H13 (equivalent to JIS S45C).
  • the nitrided sample was prepared by three hours of glow discharge nitriding (ion nitriding) at 555°C.
  • the samples were each 7 mm in diameter. They were immersed in a bath of molten borax containing 20% by weight of Fe-V powder and having a temperature of 900°C for from 30 minutes to 16 hours.
  • the cross-sectional examination of the samples for layer thickness indicated that a surface layer grew at a faster rate (about 1.5 times faster) on the nitrided sample than on the unnitrided sample.
  • a surface layer of V (C, N) and an inner layer composed of a ferrous alloy containing nitrogen and located immediately below the surface layer were formed in the nitrided sample.
  • Example 1 The procedures of Example 1 were repeated for the preparation of unnitrided and nitrided samples made of alloy tool steel for hot forming use, AISI H13 (equivalent to JIS SKD61). They were immersed in a bath of molten borax containing 20% by weight of iron-niobium-tantalum (Fe-Nb-Ta) powder for 30 minutes to four hours. The formation of 4 and 5 ⁇ m thick layers required one and two hours, of immersion for the carbide layer formation, respectively, on the nitrided sample, and two and four hours, respectively, on the unnitrided sample.
  • AISI H13 alloy tool steel for hot forming use
  • a nitrided sample made of alloy tool steel for hot forming use, AISI H13 (equivalent to JIS SKD61) was prepared as described in Example 1, and subjected to molten salt electrolysis. Namely, it was immersed in a bath of molten borax containing 10% by weight of niobium oxide (Nb z 0 5 ) and having a temperature of 1000°C. The sample was employed as a cathode and subjected to two hours of electrolysis at a cathode current density of 0.05 A/cm 2 in a graphite vessel employed as an anode.
  • a layer having a smooth surface (as shown by the microphotograph of Figure 5 was formed, and it was found to be composed of a carbonitride Nb (C, N).
  • An inner layer (composed of a ferrous alloy containing nitrogen) was found to exist immediately below the surface carbonitride layer, as was also the case in the following examples.
  • the X-ray microanalysis of the layer indicated that it was a layer of the carbonitride expressed as V (C, N), as shown in Figure 6.
  • the microscopic examination of the sample revealed the presence of a structure containing nitrogen in the area of the article adjoining the carbonitride layer.
  • a sample made of alloy tool steel for cold forming use, AISI D2 (equivalent to JIS SKD11) in the shape of a round bar was subjected to gas soft nitriding at 570°C for 150 minutes, and was subjected to powder packing, i.e. buried in a powder mixture consisting of Fe-V powder and 10% by weight of potassium borofluoride (KBF 4 ) powder, having a particle size of -100 mesh and placed in a stainless steel vessel.
  • the vessel was heated at 600°C for 16 hours in an atmospheric furnace. After the vessel had been taken out of the furnace and air cooled, the sample was taken out of the powder.
  • the sample was found by X-ray microanalysis to have a layer composed of V, N and C as shown in Figure 7, i.e., a layer of the carbonitride expressed as V (C, N).
  • a layer composed of V, N and C was found on this sample, too, as shown in Figure 8, and this V (C, N) layer was formed on the outermost surface of the sample.
  • a layer composed of V, N and C was formed as shown in Figure 9.
  • the X-ray diffraction of this surface layer revealed diffraction lines indicating VC and VN, and thereby confirmed that the surface layer was composed of the carbonitride expressed as V (C, N).
  • a slurry was formed from a powder mixture consisting of 40% by weight of alumina (AI 2 0 3 ), 55% by weight of Fe-V and 5% by weight of ammonium chloride (NH 4 CI) by using a solvent prepared by dissolving ethyl cellulose in ethyl alcohol.
  • the slurry was applied in a thickness of 3 to 5 mm onto a sample made of carbon tool steel, AISI W 1-9 (equivalent ot JIS SK4) which had been gas nitrided as described in Example 7.
  • the sample was placed in a stainless steel vessel, and heated at 1000°C for five hours in an argon gas atmosphere.
  • the surface layer thereby formed was found by X-ray microanalysis to be composed of V (C, N).
  • a powder mixture consisting of 60% by weight of alumina (AI 2 0 3 ), 38.8% by weight of Fe-V and 1.2% by weight of NH 4 CI was placed in a fluidizing furnace, and fluidized by the argon gas introduced into the furnace through the bottom thereof.
  • a layer of the carbonitride V (C, N) was formed on the bar, as shown in Figure 11.
  • a standard thread-cutting tap made of high speed tool steel, AISI M2 (equivalent to JIS SKH9) and having a pitch diameter of 8 mm was dipped in a bath of molten borax containing 30% by weight of V 2 0 5 and 15% by weight of B 4 C, and treated at 1025°C for an hour, whereby a vanadium carbide layer was formed on the surface of the tap.
  • the tap was then heated at 1190°C for 30 minutes in a vacuum furnace and thereafter gas hardened.
  • the tap was subjected to salt bath soft nitriding at 560°C for 20 minutes, and treated in a bath of molten borax as hereinabove described, whereby a vanadium carbonitride layer was formed on the surface of the tap. The tap was then hardened.
  • the tap treated in accordance with this invention and a commercially-available nitrided tap were tested for thread cutting in carbon steel material, AISI 1045 (equivalent to JIS S45C), and the life of each such tap was examined. About 1500 holes could be cut by the commercially-available tap, about 2500 holes by the tap on which the carbide layer had been formed, and about 3000 holes by the tap on which the carbonitride layer had been formed. This example also established that a ferrous alloy layer containing nitrogen could be formed immediately below the surface layer in accordance with this invention and enabled the satisfactory hardening and quenching of a ferrous alloy article.
  • this invention makes it possible to form a surface layer composed of the carbonitride of at least one element selected from V, Nb, Ta and an inner layer of a ferrous alloy containing nitrogen in a ferrous alloy article by nitriding it and introducing said element to combine it by thermal diffusion with the nitrogen and carbon in the ferrous alloy.
  • the carbonitride layer defines a surface having good properties, and the inner layer enables the material immediately below the surface layer to be hardened and quenched satisfactorily.
  • the treatment of this invention can be carried out very quickly. This invention is particularly useful if applied to cutting tools, as it can greatly prolong their life.

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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)
EP19840103561 1983-04-08 1984-03-30 A method for surface hardening a ferrous-alloy article and the resulting product Expired EP0122529B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP62796/83 1983-04-08
JP6279683A JPS59190355A (ja) 1983-04-08 1983-04-08 鉄合金材料の表面硬化処理方法

Publications (2)

Publication Number Publication Date
EP0122529A1 EP0122529A1 (en) 1984-10-24
EP0122529B1 true EP0122529B1 (en) 1987-03-18

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EP19840103561 Expired EP0122529B1 (en) 1983-04-08 1984-03-30 A method for surface hardening a ferrous-alloy article and the resulting product

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EP (1) EP0122529B1 (enrdf_load_stackoverflow)
JP (1) JPS59190355A (enrdf_load_stackoverflow)
AU (1) AU542081B2 (enrdf_load_stackoverflow)
CA (1) CA1218585A (enrdf_load_stackoverflow)
DE (1) DE3462701D1 (enrdf_load_stackoverflow)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU570799B2 (en) * 1984-05-17 1988-03-24 Toyota Chuo Kenkyusho K.K. Vapour phase coating of carbide in fluidised bed
DE3668913D1 (de) * 1985-06-17 1990-03-15 Toyoda Chuo Kenkyusho Kk Verfahren zur behandlung der oberflaeche von eisenlegierungsmaterialien.
JPS6270561A (ja) * 1985-09-24 1987-04-01 Toyota Central Res & Dev Lab Inc 鉄合金材料の表面処理方法
JPS6280258A (ja) * 1985-10-03 1987-04-13 Toyota Central Res & Dev Lab Inc 表面処理方法及びその装置
US4818351A (en) * 1986-07-30 1989-04-04 Kabushiki Kaisha Toyota Chuo Kenkyusho Method for the surface treatment of an iron or iron alloy article
CN105331926B (zh) * 2015-11-05 2018-03-20 广西大学 用于45钢表面强化的N‑C‑Cr‑V‑RE多元共渗材料

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2000814B (en) * 1977-07-07 1982-03-17 Toyoda Chuo Kenkyusho Kk Coating ferrous articles
JPS5514839A (en) * 1978-07-14 1980-02-01 Kawasaki Heavy Ind Ltd Treating method for ion nitriding
GB2055404B (en) * 1979-06-26 1983-02-16 Lucas Industries Ltd Gas nitriding steel
US4342605A (en) * 1979-07-05 1982-08-03 Honda Giken Kogyo Kabushiki Kaisha Gas soft-nitriding method

Also Published As

Publication number Publication date
JPS622628B2 (enrdf_load_stackoverflow) 1987-01-21
DE3462701D1 (en) 1987-04-23
JPS59190355A (ja) 1984-10-29
AU2633784A (en) 1984-10-11
EP0122529A1 (en) 1984-10-24
CA1218585A (en) 1987-03-03
AU542081B2 (en) 1985-02-07

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