JP2007191751A - Coating film deposition method, and coating base material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for depositing a coating film having high durability which is improved in the seizure resistance compared with a hard ceramic film such as a conventional film formed of chromium nitride, and a coating base material. <P>SOLUTION: A base material covered by a nitride film containing chromium is subjected to oxidation by a physical vapor deposition method. An oxide film containing chromium or an oxynitride coating film containing chromium is deposited on a surface layer and metal components are eliminated therefrom to enhance the seizure resistance. Bubble-like projecting parts of pin holes generated by the oxidation are removed, and a large number of pores are formed in the coating film surface to retain lubricating oil. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming a chromium-containing nitride film having fine pores in the surface layer exhibiting high seizure resistance and sliding characteristics in a lubricating oil environment and in an environment where lubrication is insufficient, and a film obtained by this method. The present invention relates to a coating substrate having the same.

  In the sliding member, parts are seized under a high surface pressure, and film peeling and wear progress accordingly. The seizure is particularly likely to occur between the same type of metals, so the sliding surface may be made of a dissimilar metal to improve seizure resistance, but hard ceramics such as chromium nitride and titanium nitride are used under high surface pressure. By coating, a method of avoiding direct contact between metals is taken. Among these hard ceramics, chromium nitride has a feature that it has low hardness compared to hard coatings such as titanium nitride, titanium carbide, titanium carbonitride, and aluminum titanium nitride, but is less attacking by the mating material. ing. In terms of low aggression, diamond-like carbon (DLC) has characteristics that the other party is less aggressive than chromium nitride and has a dry friction coefficient of 0.1 or less, but there are problems in adhesion strength and heat resistance. For this reason, chromium nitride films are used as wear-resistant sliding coatings for piston rings and rotary compressor vanes.

The concern when applying PVD coating thin films to sliding parts is their durability, and their stabilization is strong under the circumstances where the load on parts is increasing due to the trend of weight reduction and resource saving. It is desired. The coating on the sliding part has a life due to wear, delamination, or seizure, and it is necessary to improve the part so that the part can function stably over a long period of time. As countermeasures, a method of nitriding the surface layer of the substrate and forming a film on which Cr ₂ N-type and CrN-type chromium nitride are mixed (for example, Patent Document 1), the mixed composition ratio of the ion plating film is peel resistant. There are known methods (for example, Patent Document 2), a method in which the orientation of CrN is the {111} plane, and one of B, O, or C is contained in the coating (for example, Patent Document 3). .

On the other hand, seizure between parts easily occurs when the lubricating oil disappears from the interface, and as a countermeasure, it is effective to make a fine oil reservoir on the surface of the base material. As such a method, for example, in Patent Document 4, fine particles are adhered to a substrate by plating, a film is formed thereon by means such as physical vapor deposition, and then the fine particles are removed, and holes for retaining a lubricant are obtained. There has been proposed a method for forming the. Non-Patent Document 1 proposes a method of forming a porous film on a substrate surface by electroplating.
JP-A-7-286589 JP-A-8-178068 JP 2000-136875 A Japanese Patent No. 3504930 `` Advanced Materials '', Vol. 15, No. 19 (2003), p.1610-1614

  However, even if countermeasures are taken with a chromium nitride film, parts that are coated with a chromium nitride film cause seizure in an environment where the surface pressure applied to the parts is high or the supply of lubricating oil is insufficient. There is.

  Moreover, when making a fine oil sump on the surface of a base material, in patent document 4, it is necessary to attach a polymer grain by a plating process, or to remove after ceramic coating, and a process is complicated and manufacturing cost is high. There is a problem to say. Furthermore, if the polymer is present on the surface of the plating film, the adhesion strength of the film formed by the physical vapor deposition method is remarkably reduced, the processing to a shape having a curved surface is difficult, or the finer the polymer particles, the more the plating is performed. There is a problem that it is difficult to uniformly disperse the base material surface during processing. Further, the method of Non-Patent Document 1 is easier to create the surface than the method of Patent Document 4, but the film hardness is less than half that of the ceramic film, and is insufficient in terms of wear resistance, so it can withstand use. There was no problem.

  SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a coating method and a coating substrate for a sliding coating having high durability, particularly with improved seizure resistance, compared to conventional hard ceramic films such as chromium nitride. That is. Furthermore, it is to provide a coating method and a coating substrate for a sliding coating that can form a fine oil sump evenly in various shapes while ensuring a high hardness sliding coating. .

  In the present invention, the above-mentioned problems are solved by providing a film forming method in which at least the uppermost layer is coated with a chromium-containing nitride film by physical vapor deposition on the surface of the substrate, and then the coated substrate is oxidized. (Claim 1).

  That is, conventionally, chromium nitride films formed by physical vapor deposition are not entirely composed of chromium nitride crystals, and generally deviate from the stoichiometric composition and some chromium exists as a metal. . This metal component is considered to cause seizure in an environment where high surface pressure and lubrication are insufficient. On the other hand, in the present invention, a nitride film containing chromium (hereinafter referred to as a chromium-containing nitride film) is formed on a substrate by a physical vapor deposition method such as an ion plating method or a sputtering method. Since the substrate is heated in an oxidizing atmosphere to convert the surface layer of the film into an oxide, at least the surface layer of the chromium-containing nitride film becomes an oxide or oxynitride, and a part of oxygen enters the film through the voids in the tissue. Also enter. By doing so, there is no free metal component at least near the surface layer, and excellent durability can be obtained even under high surface pressure in a lubricating oil.

  Chromium is originally a material with high oxidation resistance, and forms chromium oxide on the surface layer as seen in stainless steel to suppress further oxidation. Therefore, for example, an oxide film can be easily formed on the surface layer by heating with an electric furnace or the like in the atmosphere, and oxidation is prevented from proceeding to the inside.

  Furthermore, in the invention according to claim 2, after coating the chromium-containing nitride film on at least the uppermost layer on the surface of the substrate by physical vapor deposition, the coated substrate is oxidized, and the oxidation treatment is further performed. The method of forming a film was to add a step of removing the bubble-shaped convex portions from the surface of the uppermost layer film.

  Usually, in a film formed by physical vapor deposition or the like, there are many pinholes reaching the substrate from the film surface. It is difficult to eliminate this pinhole. In the present invention, this pinhole is utilized as an advantage. That is, by heating the chromium-containing nitride film having pinholes in an oxidizing atmosphere, the base material comes into contact with the oxidizing gas through the pinholes existing in the film, and the base material immediately below the holes is oxidized. As a result, the oxidized base material expands in volume, and the film coated thereon floats. The floated film forms a foamy convex part. This foamy convex part can be removed and smoothed by a simple operation such as friction. By removing and smoothing this foamy convex part, the surface has many fine holes. A film can be formed.

  For example, FIG. 1 shows a surface photograph of a chromium nitride film manufactured by magnetron sputtering on a hot mold steel SKD61 substrate. When a base material coated with a film having a pinhole as shown in this figure is placed in an oxidizing atmosphere, the base material is oxidized through the pinhole, and the base material immediately below the pinhole expands and is formed thereon. The film is lifted. By removing the foamy convex portions of the floated film by a method such as friction, a film having holes that become oil pools can be easily formed. The diameter of the holes thus generated varies depending on the processing conditions. As shown in FIG. 3 described later, when heated in an air atmosphere at 500 ° C. for 1 hour, the thickness of the oxide layer is 0.2 μm and the hole diameter is Distribution of 10 to 200 μm.

  In the invention described in claim 3, the chromium content ratio in the metal element of the at least uppermost chromium-containing nitride coating is 10 wt% or more. The alloy element content of chromium having a function of suppressing the progress of oxidation to the inside while forming an oxide film on the surface layer of the substrate is preferably 10 wt% or more, and if it is less than that, the entire film is oxidized and the film itself This is because the characteristics change. Further, the chromium-containing nitride film of the present invention needs to contain at least chromium. Therefore, in the invention described in claim 4, the alloy element other than chromium in the metal element of the at least uppermost chromium-containing nitride film is one or two selected from 4a, 5a, 3b, and 4b groups. A hard alloy film of chromium and chromium was formed.

  Furthermore, in the invention described in claim 5, the oxidation treatment is performed by a method of heating in air, water vapor or oxygen atmosphere. According to this, a simple apparatus may be sufficient. In the invention described in claim 6, the oxidation treatment temperature is set to 300 ° C. or higher and lower than 1000 ° C. Although the thickness of the oxide film increases with time, once the oxide film is formed on the surface layer, diffusion of oxygen into the film is suppressed, so that the increase in thickness is delayed with time. Therefore, in order to form a thick oxide film, a method of increasing the processing temperature to about 500 ° C. is effective, and a thick film can be formed in a short time. Since the oxidation treatment temperature also affects properties such as the strength and hardness of the base material, it is necessary to pay attention. However, practically, the temperature is not less than 300 ° C. and less than 1000 ° C.

  Furthermore, in the invention described in claim 7, the base material is a steel base material, and after the base material is nitrided, a coating treatment, an oxidation treatment or the like is performed. By using high-speed tool steel or a material having high heat resistance, or by nitriding the steel, softening due to heating is suppressed, and the base material is prevented from being softened by the processing temperature at the time of forming the oxide film of the present invention.

  The following coated substrate is provided by the above-described film forming method of the present invention. That is, in the invention described in claim 8, at least the uppermost layer of the substrate surface has a chromium-containing coating, and the surface layer of the chromium-containing coating includes a chromium-containing oxide film or a chromium-containing oxynitride film. A coated substrate having a metal ratio of 0.01 atomic% or less is provided. Since the surface layer is oxidized to be a chromium-containing nitride film and a chromium-containing oxynitride film, the sliding performance is good, and the ratio of the metal such as chromium metal or metal other than chromium, for example, aluminum metal is 0. Since there is no metal component in a substantially free state of 01 atomic% or less, it has high sliding performance and durability.

  In the invention according to claim 9, a microporous hole is formed on the surface of the base material, and the microporous surface is a coated base material including a chromium-containing oxide film or a chromium-containing oxynitride film. This is obtained by the film forming method according to claim 2. Since the inner surface of the hole is not a mere minute hole but a chromium oxide film or a chromic oxynitride film, the occurrence of rust or the like is small, and the chemical change due to the lubricant or the like is small. Furthermore, in the invention described in claim 10, the coated base material has a thickness of the oxide layer of 0.05 to 0.5 μm and a pore size distribution of 10 to 200 μm. As described above, this does not require much control of generation or suppression of pinholes during physical vapor deposition. Moreover, the hole diameter of the minute hole is suitable for the size of the oil sump for lubrication. If the thickness of the oxide layer is 0.05 μm or less, free metal components may remain. If the thickness exceeds 0.5 μm, the surface may be deteriorated due to oxidation, so the thickness of the oxide layer is 0.05 or more. 0.5 μm or less is preferable.

  Furthermore, in the invention described in claim 11, the chromium content ratio in the metal element of the uppermost chromium-containing coating is 10 wt% or more, thereby providing a stable film. In the invention described in claim 12, the alloy element other than chromium in the metal element of the chromium-containing coating of the uppermost layer is one or more selected from 4a, 5a, 3b, and 4b groups. Is preferred. In the invention described in claim 13, the base material is a steel base material, which has been subjected to nitriding treatment, and has no reduction in strength.

  As described above, in the present invention, by providing a film forming method for oxidizing a substrate coated with a chromium-containing nitride film, free metal components near the surface layer are eliminated, and seizure resistance is improved. Thus, a sliding member with improved durability and high durability can be easily manufactured with high and stable quality. Furthermore, the invention according to claim 2 provides a method of forming a film having a large number of pores on the surface by adding a step of removing the bubble-shaped convex portions from the surface of the oxidized uppermost layer film. Therefore, a large number of fine oil sumps can be easily and uniformly manufactured. In addition, since it can be realized by a relatively simple method such as appropriately using a conventional apparatus, there is an effect that it is possible to provide a sliding coating excellent in seizure resistance and a member coated therewith at a low cost.

  In the invention described in claim 3, the chromium content is set to 10 wt% or more, and while the oxide film is formed on the surface layer of the substrate, the progress of oxidation to the inside is suppressed, and the oxidation of the film and the characteristics of the film are performed. Therefore, a stable sliding member can be provided. In addition, since the alloy element other than chromium in the metal element of the chromium-containing nitride film may be a hard alloy film of one or more selected from the group 4a, 5a, 3b, and 4b and chromium, the characteristics of chromium can be improved. Various coating equipment used can be provided.

  In the invention described in claim 5, since the oxidation treatment may be a simple apparatus that heats in the air, water vapor or oxygen atmosphere, the operation is easy and the treatment can be performed at low cost. In the invention described in claim 6, the oxidation treatment temperature is set to 300 ° C. or more and less than 1000 ° C. so that a thick film can be formed. Further, in the invention described in claim 7, the steel substrate is nitrided. Since the treated base material is subjected to coating treatment, oxidation treatment, etc. to prevent softening of the base material, it is possible to provide a coated base material that reduces the influence on the strength and hardness of the base material and takes advantage of the properties of the base material.

  In the invention described in claim 8, the surface layer of the chromium-containing coating film includes a chromium-containing oxide film or a chromium-containing oxynitride film so that the metal ratio of the surface layer is 0.01 atomic% or less, Eliminates metal components in a free state, prevents seizure when sliding against the mating metal material even in an environment where oil lubrication is insufficient, and has high sliding performance and durability. It has a load resistance and high durability, and is a coated substrate particularly suitable for a sliding member. Furthermore, in the invention described in claim 9, a micropore having the surface of the chromium-containing oxide film or the chromium-containing oxynitride film is provided on the surface of the base material, and an oil sump having chemical resistance is formed. As a result, the retention of the lubricant has been increased, and the seizure resistance has been further improved, making it useful as a coating substrate for sliding.

  Furthermore, in the invention described in claim 10, the thickness of the oxide layer is 0.05 to 0.5 μm, the pore size distribution is 10 to 200 μm, and the pore size is suitable for oil sump. Due to its size, it became more suitable for sliding. In the invention described in claim 11, since the chromium content is 10 wt% or more and a stable film is obtained, there is no peeling or rusting. In the invention described in claim 12, the alloy element other than chromium in the metal element of the chromium-containing coating of the uppermost layer is one or more selected from 4a, 5a, 3b, and 4b groups. Therefore, various sliding coated substrates can be provided. For example, in addition to chromium nitride, similar characteristics can be obtained with a film containing chromium, such as aluminum chromium nitride and chromium nitride titanium. A similar function can be obtained in the same way by forming a gradient composition layer structure in which the lower layer in contact with the base material is made of titanium metal or chromium metal, gradually increasing the nitrogen component, and then oxidizing. In the invention according to claim 13, since the steel substrate is subjected to nitriding treatment to reduce the strength reduction, a high-strength sliding coating substrate can be provided.

  Next, the best mode for carrying out the present invention will be described.

  Example 1 of the present invention uses a chromium plating steel SCM415 base material that has been ground using a metal chromium as an evaporation material and nitrogen as a reaction gas, and a high-speed tool that has been lapped using an ion plating apparatus that dissolves the evaporation material. A chromium nitride film (CrN film) having a thickness of 3 μm was coated on the steel SKH51. As a result, a film having a large number of pinholes on the surface was obtained as shown in FIG.

  Next, this base material was put into an electric furnace in an air atmosphere and heated at 500 ° C. for 30 minutes. As a result, it was found that the color tone of the SKH51 base material changed from a metal color to a blue color and the surface layer was oxidized, but there was no other recognizable change in surface properties. The concentric circles shown in FIG. 2 were used to examine the thickness of the oxide layer, and a trace of a smooth polished SKH51 substrate sample was cut from the surface of the membrane toward the substrate using a carotester. Carotest marks. From FIG. 2, the thickness of the oxide layer on the substrate surface was about 0.2 μm.

  On the other hand, as shown in FIG. 3, in the SCM415 base material, a number of oxidation marks appeared on the surface of the base material that had been polished smoothly after oxidation. As described above, this is caused by oxidation of the base material directly below the pinhole through the pinhole of the film. Many pinholes having a thickness of 10 to 80 μm are generated. The difference between SKH51 and SCM415 is thought to be due to the difference in the pinhole size of the produced film and the oxidation resistance of the substrate.

  FIG. 4 shows a photograph of a surface and a calotest mark after a cemented carbide base material is coated with an aluminum chromium nitride film (AlCrN film), heated at 1000 ° C. for 1 hour in an air atmosphere, and then polished smoothly. FIG. 3 shows traces of a spherical shape from the film surface toward the substrate using a carotester as in FIG. 2. Cemented carbide is a base material having higher oxidation resistance than SKH51. However, when heated to 1000 ° C. in the atmosphere, oxidation proceeds through pinholes in the aluminum nitride chromium film, and pores are generated in the film. Recognize.

A chromium nitride film and an aluminum nitride chromium film are formed on a chromium molybdenum steel SCM415 base material that has been φ6 × 40 ground by the method shown in Example 1, and then heated to 500 ° C. in the atmosphere using an electric furnace. Then, the cylindrical surface was polished so that the cylindrical surface became smooth. Next, the anti-seizure performance of the base material of the present invention was evaluated using a Falex test apparatus whose main part is shown in FIG. Further, as a comparative example, a test was similarly performed on a base material coated with a chromium nitride film, an aluminum chromium chromium film, and a titanium nitride film that were not oxidized. In the test, automatic transmission oil was applied to the base material 1 immediately before the start of the Falex test, and then the round bar base material was rotated at 300 rpm, and loads 3 and 3 were applied through the V block 2 pressing the round bar from both sides. It was. The load was increased at a constant speed, and after reaching 400 kgf, the load was held and the time until the rotational torque increased was measured. By this test, the results shown in Table 1 were obtained.

  Table 1 shows the evaluation results of seizure resistance by the Falex test. As shown in Table 1, the durability of the product of the present invention was 50 seconds in the case of the chromium nitride film and 45 seconds in the aluminum chromium nitride film, while the oxidation treatment as a comparative example was performed. In the case of the non-chromium nitride film and the aluminum nitride chromium film, only the durability time of about 15 seconds and 14 seconds can be obtained, and in the case of the titanium nitride film not containing chromium, the durability time is only about 11 seconds and 1/5. It was not obtained. Thus, it can be seen that the chromium-containing nitride film subjected to the oxidation treatment of the present invention has excellent seizure resistance characteristics.

  Although the present invention has been described based on the embodiments, the present invention is not limited to these specific forms, and the described forms can be variously changed within the definition of the appended claims, or The present invention can be implemented in other forms.

It is the surface photograph of the chromium nitride film | membrane produced by the magnetron sputtering method. It is the surface photograph of the Calotest trace for investigating the film thickness of the chromium nitride film | membrane which performed the oxidation process of this invention. It is the surface photograph of the chromium nitride film | membrane which grind | polished smoothly after the oxidation process of this invention. It is a photograph which shows the surface of the aluminum chromium nitride film | membrane polished smoothly after the oxidation treatment of this invention, and a Calotest trace. It is a Falex test schematic.

Claims (13)

A method for forming a film, comprising: coating a substrate surface with a chromium-containing nitride film on at least an uppermost layer by physical vapor deposition, and then oxidizing the coated substrate. After coating a chromium-containing nitride film on at least the uppermost layer on the surface of the substrate by physical vapor deposition, the coated substrate is oxidized, and further, bubble-shaped protrusions are formed from the surface of the oxidized uppermost layer film. A method of forming a film, comprising adding a step of removing. 3. The film forming method according to claim 1, wherein the chromium content in the metal element of the at least uppermost chromium-containing nitride film is 10 wt% or more. The alloy element other than chromium in the metal element of the at least uppermost chromium-containing nitride film is one or more selected from the group consisting of 4a, 5a, 3b, and 4b. 4. The method for forming a film according to any one of 3 above. The film forming method according to any one of claims 1 to 4, wherein the oxidation treatment is performed by a method of heating in air, water vapor, or oxygen atmosphere. The film forming method according to claim 1, wherein the oxidation treatment temperature is not less than 300 ° C. and less than 1000 ° C. The said base material is a steel base material, After performing the nitriding process of the said base material, the film formation method as described in any one of Claims 1 thru | or 6 is performed. A chromium-containing coating is provided on at least the uppermost layer of the substrate surface, and the surface layer of the chromium-containing coating includes a chromium-containing oxide film or a chromium-containing oxynitride film, and the ratio of the surface metal is 0.01 atomic% or less. A coated substrate characterized by the above. The coated substrate according to claim 8, wherein micropores are formed on the surface of the substrate, and the microporous surface includes a chromium-containing oxide film or a chromium-containing oxynitride film. 10. The coated substrate according to claim 9, wherein the thickness of the oxide layer is 0.05 to 0.5 [mu] m, and the pore size distribution is 10 to 200 [mu] m. The coated base material according to any one of claims 8 to 10, wherein the chromium content in the metal element of the uppermost chromium-containing coating is 10 wt% or more. The alloy element other than chromium in the metal element of the uppermost chromium-containing coating is one or more selected from the group of 4a, 5a, 3b, and 4b, 12 or any one of claims 8 to 11 A coated substrate according to any one of the above. The coated substrate according to any one of claims 8 to 12, wherein the substrate is a steel substrate and is nitrided.