JP2002249866A - Wear resistant ferrous film with excellent toughness, and method for its deposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrous film having excellent toughness and wear resistance and provide a method for its deposition. SOLUTION: The wear resistant ferrous film with excellent toughness is deposited on the surface of a base material and contains >=10 vol.% austenite phase and also contains at least Fe, Ni, Cr and N. In this film deposition method, an alloy target containing Fe, Ni and Cr is used in depositing the film on the base material and the film is deposited on the surface of the base material in a nitrogen-containing plasma atmosphere under >=8 mTorr partial pressure of nitrogen by a vapor plating process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron-based coating having both excellent toughness and wear resistance and a method for forming the same, and more particularly, to a high wear resistance in the fields of transport equipment, industrial machinery, leisure goods and the like. Tools, axles, bearings,
The present invention relates to an iron-based coating useful for improving the toughness and wear resistance of mechanical parts including various sliding and rolling elements such as constant velocity joints and rail guides, and a method for forming the same.

[0002]

2. Description of the Related Art In order to cope with severe use environments in recent years, various mechanical parts such as sliding members and rolling members are required to have not only hardness but also high toughness. As such a technique, for example, Japanese Patent Laid-Open No. 5-78821 discloses Co, Ni and Mo.
At least one metal selected from the group consisting of Si, Ti, V, and C
Abrasion resistance and film toughness are improved by coating a film composed of a mixed structure of at least one metal selected from the group consisting of r, Fe, Zr, Nb and W with a carbide or nitride of the metal by ion plating. Techniques for improving have been proposed. Japanese Patent Application Laid-Open No. 5-125521 discloses that TiN and N
A technique has been disclosed in which a coating made of i is coated on the surface of a base material by an ion plating method to improve adhesion. Japanese Patent Application Laid-Open No. Hei 9-71856 discloses Al, Si, F
e, at least one metal selected from the group consisting of Ti, V, Cr, Zr, Nb, Hf and W, selected from the group consisting of Co, Ni, Mo and Cu in carbides, nitrides or carbonitrides A method of improving the toughness and adhesion by coating a coating containing at least one kind of metal on the surface of a base material by an ion plating method has been proposed.

[0003]

SUMMARY OF THE INVENTION These proposed techniques are based on Ni, Co, Mo, and Ni in order to secure sufficient toughness.
It is necessary to add a large amount of expensive metal such as Cu, which is a factor of high cost. In particular, when using a gas phase coating method such as an ion plating method or a sputtering method for film formation, a target material having a special composition is melted,
Alternatively, a complicated film forming operation using a plurality of types of targets is required, and the manufacturing cost is significantly increased. Therefore, the application has been limited to some high-end products.

[0004] Further, since a wear-resistant member provided with a film according to the prior art is used in the presence of a lubricating oil, the lubricating oil is designed for components such as additives on the assumption that the lubricating oil is applied to steel parts.
However, if the main component of the coating is other than Fe, the compatibility between the lubricating oil and the film is poor, and the lubricating oil is degraded. For example, if the film contains a large amount of Ni, Ni reacts with the S-based extreme pressure agent in the lubricating oil, and Ni
Since sulfides are generated to blacken the lubricating oil and the extreme pressure agent is consumed, there is a problem that the life of the lubricating oil is significantly reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an iron-based film having excellent toughness and wear resistance, and to provide a method for forming the film.

[0006]

Means for Solving the Problems The film of the present invention which can solve the above-mentioned problems is that the film contains an austenite phase of 10 vol% or more, and at least Fe, Ni, Cr, N
It has a gist in containing. At this time, it is recommended that the average surface hardness of the coating is Hv900 or more.
Further, it is desirable that N contained in the film be 4% by mass or more and satisfy the following formula. Nitride content (vol%) ≧ −1.44 × N content (mass%) + 13 The film of the present invention can be formed on the surface of a base material and used as a film coating material.

In forming the film of the present invention on a base material,
It is recommended to coat the base material surface by a vapor phase coating method using an alloy target containing Fe, Ni, and Cr in a plasma atmosphere containing nitrogen under a nitrogen partial pressure of 8 to 30 mTorr. At this time, it is desirable that the cathode voltage at the time of the vapor phase coating be 60 A or more and less than 100 A.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have focused on the fact that the structure of a coating film is important for maximizing the film performance in order to solve the above-mentioned problems of the prior art.
As a result of intensive studies on the relationship between the structure, toughness, and wear resistance of the Cr—Ni-based nitrogen film, it has been found that a film containing Fe having a specific structure and a specific element has excellent toughness and wear resistance. Heading, and led to the present invention. Hereinafter, the present invention will be described in detail.

The film of the present invention is a film formed on the surface of a base material, and has a gist that the film contains an austenite phase of 10 vol% or more and contains at least Fe, Ni, Cr and N.

[0010] The components contained in the coating of the present invention, Cr, Ni
The balance excluding N and N is substantially Fe, and the Fe content may be appropriately adjusted according to the purpose of use.
The e content is not particularly limited. As the Fe content increases, the compatibility between the film and the lubricating oil can be improved. Therefore, it is recommended that the Fe content in the film be at least 50% by mass. The hardness of the coating is improved by adding Cr and N to the coating of the present invention, but the toughness of the coating is reduced with the increase in hardness. Therefore, in order to improve the hardness without lowering the toughness of the film, it is necessary that the Fe structure in the film has a structure containing an austenitic phase (hereinafter, sometimes referred to as “γ phase”). The ratio of the γ phase is not particularly limited, but at least 10 vol% of the Fe structure contained in the film must be the γ phase in order to obtain the required toughness and wear resistance. Preferably it is 20 vol% or more. The upper limit is not particularly limited.
All of the Fe structures may be in the γ phase. If the γ phase is contained in the above ratio, the remainder may be a precipitate or the like, and is not particularly limited.

In the present invention, the content of the γ phase is determined by XRD (X
Line diffraction). In many cases, the γ phase contains N exceeding the solid solubility limit. By forming the γ phase containing N in supersaturation, it is possible to increase the hardness and toughness of the film. When N is dissolved in the γ phase, the peak of the γ phase measured by XRD shifts to the lower angle side. The shift amount reflects the N solid solution amount of the γ phase, and the relative sensitivity coefficient is determined by a simulation based on the Rietveld method on the result of XRD peak separation, and the γ phase is determined by a method of quantifying each phase. Quantify the amount. Whether or not N is in a supersaturated state can be confirmed by performing a heat treatment and measuring whether or not a precipitated phase such as a nitride is generated by XRD or the like.

Ni contained as a component of the coating of the present invention
Is a component that promotes the formation of a γ phase, and is particularly effective in improving toughness. To achieve these effects, Ni
And the Ni content is not particularly limited. However, if the Ni content is small, sufficient toughness may not be ensured even when the ratio of the γ phase is high, so that the Ni content is preferably 2.5%.
It is desirable that the content be at least 4% by mass, more preferably at least 4% by mass. The upper limit of the Ni content is not limited from the viewpoint of promoting the generation of the γ phase. However, since Ni is an expensive element, adding a large amount thereof causes a cost increase.
Further, since the effect of addition tends to be saturated, it is recommended that the upper limit be 30% by mass. At this time, the upper limit is desirably set to 10% by mass from the viewpoint of exerting a sufficient Ni addition effect while preventing deterioration of the lubricating oil due to Ni.

N contained as a component of the film of the present invention is
Like Ni, it is a component that promotes the formation of the γ phase,
It is a component that improves the hardness of the iron-based coating. By containing N, the wear resistance and the toughness of the film can be improved. The amount of N contained in the film is not particularly limited, but is preferably 4% by mass or more, more preferably 5% by mass or more, in order to sufficiently obtain the effect of promoting the formation of the γ phase and the effect of improving the hardness. The upper limit of the amount of N is not particularly limited, but is preferably 20% by mass,
More preferably, the upper limit is 15% by mass.

Cr contained as a component of the coating of the present invention
Is a component for improving the hardness of the iron-based coating, and is a component necessary for improving the wear resistance of the coating. The Cr content is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, in order to obtain a sufficient effect of improving the film hardness. The upper limit is not particularly limited, but if Cr is contained in a large amount relative to Ni, the formation of the γ phase may be inhibited, and the film itself may become brittle. More preferably, the upper limit is set to 20% by mass.

In the present invention, "the balance is substantially Fe" refers to C, B, P, S normally contained in an Fe-based alloy.
The purpose is that i, S, Nb, etc. and other metal elements and their nitrides, carbides or carbonitrides may be mixed into the matrix and contained in a range that does not greatly affect the properties of the film. Also, the case where an oxide or a boride is mixed within a range that does not greatly affect the properties of the film is within the scope of the present invention.

The film thickness of the film according to the present invention is not particularly limited, and the necessary film thickness may be selected according to the use environment, applicable members, required dimensional accuracy and the like. When the film thickness is extremely thin or conversely, when the film thickness is extremely large, a sufficient effect of the film may not be obtained. Therefore, the film thickness is preferably 2 μm or more, more preferably 5 μm or more, preferably 50 μm or less, more preferably 20 μm or less.

The type of the base material to be coated with the film according to the present invention is not particularly limited, and may be Fe-based alloys such as steel for machine structures, steel for tools, and bearing steel; Alloys, super hard materials, ceramics and the like can be used. Of these, materials having high hardness are preferable,
If it has a high hardness, even if it is used in an environment where a local surface pressure is applied, it is possible to prevent the destruction and peeling of the film due to deformation of the base material. In order to suppress the shear stress generated at the film / substrate interface when the film is deformed, it is preferable that the Young's modulus difference between the film of the present invention and the base material is small. The adhesion can be maintained even if the shear stress generated at the interface becomes high. From such a viewpoint, it is preferable to use an Fe-based substrate, and more preferably, an Fe-based substrate having high hardness. Hardness is Hv6 as base material
A material having a value of not less than 00 is recommended, and an Fe-based alloy having an Hv of not less than 900 is particularly preferable.

In the present invention, the hardness of the film is at least H
Preferably it has a v900. When Hv900 or more, when a nitrided steel or a carbonitrided steel is used as the wear-resistant member, a film having a hardness approximately equal to the hardness of the base material can be formed and can be used for a wide range of applications. The hardness of the coating is preferably Hv1000 or more in order to be applied to a field requiring more excellent wear resistance.

It is recommended that the film having excellent abrasion resistance and toughness has a hardness of not less than Hv900 and a film component satisfying the following formula. Iron-based nitride content (vol%) ≧ −1.44 × N content (% by mass) +13 and N content (% by mass) ≧ 4

As long as the film satisfies the above formula, the solution hardness and toughness can be more effectively improved by precipitation of solid solution N and nitride, and excellent toughness is maintained even when the hardness is Hv900 or more. be able to.

The nitride contained in the film according to the present invention
However, preferably 300 nm or less, more preferably 100 nm
If it exists in a fine state of less than nm,
The effect of improving degree and toughness is obtained. In addition, raw nitride
The amount, form, type, etc. are determined by the energy input during film formation (nitriding
Energy that promotes product formation)
In the invention, the effect of nitride is on the hardening by precipitation
The type of the nitride is not particularly limited. As nitride
Fe_TwoN, Fe_ThreeN, Fe_FourN and (Fe ・ Cr)_TwoN
_1-x(Composite nitride, where x is a number less than 1.)
And the like.

As a method of coating the base material with the film according to the present invention, reactive plasma spraying can be used. However, it is recommended to use a gas phase coating method, and the density of the film and the process From the viewpoint of the degree of freedom in setting, an ion plating method or a sputtering method is desirable.

In the present invention, the film may be formed in a plasma atmosphere containing nitrogen by using a target containing Fe, Ni, and Cr. More specifically, a target which uses nitrogen or a nitrogen-containing gas such as a nitrogen-methane mixed gas as a process gas at the time of film formation, generates plasma in the process gas atmosphere, and evaporates or scatters toward the base material The film according to the present invention can be formed on the base material by forming a film while reacting the material with the plasma.

As the target material, Fe, Ni, Cr
For example, commercially available austenitic stainless steel or alloy steel such as nickel-chromium molybdenum steel can be used as such a target material. In the present invention, a commercially available iron-based alloy can be used as a target material, so that it is not necessary to melt a special alloy, and it is not necessary to perform a complicated film forming operation using a plurality of types of targets. Is also excellent. At this time, in order to keep the film in a non-equilibrium state containing supersaturated N, it is recommended to set the base material temperature and the bias voltage at the time of film formation low, but if the bias voltage is too low, the film In some cases, a voltage of −80 V or more and −30 V or less is desirably used because the compactness of the steel may decrease and the toughness may decrease. The temperature of the base material varies depending on the composition of the target alloy and the film forming conditions. However, in order to suppress the formation of nitrides as much as possible and to stabilize the γ phase, it is preferable that the maximum temperature during film formation be less than 200 ° C. When the temperature is 200 ° C. or higher, a ferrite phase (α phase) is easily generated, and
It is difficult to generate a γ phase. In addition, the toughness of the coating deteriorates, which is not preferable.

In order to promote the formation of the γ phase and to suppress the formation of nitrides in the γ phase, it is desirable to lower the cathode current during film formation. Since the rise in the temperature of the base material can be suppressed by lowering the cathode current, the formation of nitrides can be suppressed, and the denseness of the film increases and the film toughness improves. The preferred cathode current is between 60 and 10
0A.

The nitrogen partial pressure during film formation is appropriately controlled to 8 m
It is recommended to be Torr or higher. If the nitrogen partial pressure is too low, the film is mainly composed of a ferrite phase (α phase), so that it is difficult to generate a γ phase, and a sufficient film hardness may not be obtained. The upper limit is not particularly limited, but if the nitrogen partial pressure is too high, the precipitation of nitrides in the γ phase is promoted, so that the ratio of the γ phase may decrease and the film toughness may decrease, so the upper limit is set to 30 mTorr. It is desirable.

Hereinafter, the present invention will be described in detail with reference to examples.
It should be noted that the following examples are not intended to limit the present invention, and all modifications and implementations without departing from the spirit of the preceding and the following are included in the technical scope of the present invention.

[0028]

[Example] Chromium molybdenum carbonitrided steel (surface hardness H
v900 or more) was used as a base material, and a film was coated on the surface of the base material by an arc ion plating method so that the film thickness was 5 μm under the conditions (target material, processing temperature during film formation) shown in Table 1 below. At this time, nitrogen was used as an introduction gas. In addition, in order to suppress nitride formation as much as possible and stabilize the γ phase, intermittent film formation is performed as necessary to suppress the maximum temperature during film formation to less than 200 ° C., and Ar gas is used for pressure adjustment. It was mixed as needed as needed.
The obtained core coating material was evaluated for film hardness (by a Micro Vickers hardness tester) and toughness (by a scratch tester). The amount of the γ phase is separately measured by the Rietveld method using XRD, the crystal grain size of the nitride is measured by TEM observation, and the N content of the coating is determined by EPMA.
Was evaluated. Table 1 shows the results. Other conditions of the film forming method are shown below.

<Arc ion plating film formation conditions> Degree of vacuum before gas introduction: 1 × 10 ⁻³ × 10 ⁻⁵ Torr Sputter cleaning: −500 to −800 V, 2 mi
n (intermittent) N ₂ partial pressure after gas introduction: 8 to 30 mTorr Cathode current at the time of film formation: 60 A or more and less than 100 A Bias voltage at the time of film formation: -5 to -100 V Temperature before film formation: 100 to 150 ° C. <Toughness evaluation method > Indenter: diamond, tip diameter 200 μmR Speed: 10 mm / min Load: 100 N / min Toughness evaluation standard: chipping load <quantitative condition by XRD> γ phase amount: used peak γ (111), (200), (220) Total strength α (200) strength Nitride (110) strength Relative sensitivity coefficient γ phase 0.1523 α phase 1.0 Fe ₃ N 1.5755 (Cr, Fe) ₂ N _1-X 1.5223

The phases identified other than the γ phase and the precipitated phase are mainly the α phase. Other unidentifiable phases were observed in some cases, but they were ignored in quantification due to their small quantity. Further, the relative sensitivity coefficient was obtained by calculating a value that fits the separation peak by a simulation by the Rietveld method. N content in γ phase: Calculate the lattice constant from peaks γ (111) and (220) used and average N (mass%) = − 116.252 + 32.618 × average lattice constant (Å) <Measurement of N content in film> Surface analysis: Analyzed from the surface in the 100 μmφ area Quantitative analysis: Fine adjustment of sensitivity using SUS304 alloy

[0031]

[Table 1]

No. 3 having a surface-treated film under the conditions specified in the present invention. In the case of 1 to 12, the film is excellent in toughness and hardness (wear resistance). In addition, as a result of TEM observation,
The crystal grain size was not more than 00 nm. On the other hand, No. 3 which is out of the scope of the present invention. In the case of 13 to 15, there is a problem in the toughness of the film (in some cases, film peeling also occurs), and as a result, sufficient performance cannot be exhibited.

[0033]

According to the present invention, it is possible to apply a surface treatment film having excellent wear resistance by an inexpensive and simple method, and as a result, it is possible to obtain a wear resistant part excellent in practical use. It is.

Continuation of the front page (72) Inventor Kenji Yamamoto 1-5-5 Takatsukadai, Nishi-ku, Kobe F-term in Kobe Steel Research Institute Kobe Research Institute (reference) 4K029 AA02 BA58 BB07 BC02 BD04 CA04 CA06 EA03 EA09

Claims (6)

[Claims] 1. A film formed on a surface of a base material, said film containing 10% by volume or more of an austenite phase and containing at least Fe, Ni, Cr, and N, and has excellent toughness. Wear-resistant iron-based coating. 2. The coating according to claim 1, wherein the average surface hardness of the coating is Hv900 or more. 3. The film according to claim 1, wherein N contained in the film is at least 4% by mass and the following formula is satisfied.
The film described in 1. Nitride content (vol%) ≧ −1.44
× N content (% by mass) +13 4. A coating material, wherein the coating according to claim 1 is formed on the surface of a base material. 5. The method for forming a film according to claim 1 on a base material, using an alloy target containing Fe, Ni, and Cr in a plasma atmosphere containing nitrogen for 8 m.
A film forming method comprising coating a base material surface by a gas phase coating method under a nitrogen partial pressure of Torr or more. 6. A cathode voltage at the time of vapor phase coating is 6
The film forming method according to claim 5, wherein the temperature is 0 A or more and less than 100 A.