JPH0424422B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a surface treatment method for forming a nitride or carbonitride layer of Group Va elements of the periodic table on the surface of iron alloy materials such as molds, jigs, tools, and machine parts. It is related to. [Prior Art] When the surface of a ferrous alloy material is coated with a surface treatment layer consisting of carbides, nitrides, or carbonitrides of group Va elements, the wear resistance, seizure resistance, oxidation resistance, and corrosion resistance of the ferrous alloy material are improved. It is well known that various properties such as Many proposals have been made in recent years regarding methods of coating this surface layer. For example,
A method has been proposed in which a surface layer consisting of carbonitrides of group Va elements is formed on the surface of iron alloy materials by plasma CVD (chemical vapor deposition) using halides of group Va elements. (For example, JP-A-55-65357, JP-A-55-154563).
In these methods, the A _c1 transformation point of iron is approximately 700
Since the treatment is carried out at temperatures below ℃, it is possible to form a surface layer without causing heat distortion to the base material of the iron alloy material, but the formed surface layer has good throwing power and adhesion. is difficult to obtain. Furthermore, the processing steps are complicated and the equipment is expensive. In addition, efficiency is poor because it must be carried out in hydrogen or reduced pressure. [Problems to be Solved by the Invention] The present invention solves the above-mentioned conventional problems, and efficiently performs heat treatment at low temperatures using extremely simple equipment, without causing distortion in the base material. The object of the present invention is to provide a method for forming a surface layer made of a nitride or carbonitride of a Group Va element that has excellent adhesion to a base material on an iron alloy material. [Means for Solving the Problems] The present invention provides a nitriding treatment to form an iron/nitrogen or iron/carbon/nitrogen nitride layer on the surface of the iron alloy material, and then a periodic treatment with the iron alloy material. Chapter Va of the Table of Laws
Materials containing group elements (vanadium, niobium, tantalum) and alkali metal or alkaline earth metal chlorides, boron fluorides, fluorides, oxides, bromides,
heat-treated at 580°C or less in the coexistence of a treatment agent consisting of one or more of iodides, carbonates, nitrates, borates, one or both of ammonium halides and metal halides; By diffusing Group Va elements into the surface of the iron alloy material, the surface of the iron alloy material is made of nitrides or carbonitrides of Group Va elements,
This is a method for surface treatment of an iron alloy material, characterized by forming a surface layer having a layer thickness depending on the conditions of the nitriding treatment. In the present invention, the iron alloy material is a material to be treated on which a nitride or carbonitride layer of Group Va elements is formed. The iron alloy material may be one containing carbon, such as carbon steel, alloy steel, cast iron, sintered alloy, or the like, or one containing very little carbon, such as pure iron. In addition, the higher the carbon content in the iron alloy material, the more Va.
The amount of carbon in the carbonitride layer of group elements also increases. Therefore, in order to increase the amount of carbon in the surface layer formed, the carbon content of the surface portion may be increased by carburizing or the like prior to nitriding, or carburizing may be performed during nitriding. Note that when industrial pure iron is used as the material to be treated, a very small amount of carbon contained in the base material enters the carbonitride layer of Group Va elements. Nitriding is the process of adding nitrogen (N) to the surface of iron alloy materials.
is diffused to form a nitride layer. This nitride layer is made of iron nitride, which is the reaction between iron and nitrogen, or iron carbonitride, which is the reaction between iron, nitrogen, and carbon in the base material. Note that a solid solution layer (diffusion layer) of nitrogen into iron is formed directly below the nitride layer. Then, by heat-treating this iron alloy material together with a material containing Group Va elements, Group Va elements diffuse into the nitride layer, and a substitution reaction occurs between Group Va elements and iron in the nitride layer. . At this time, if the nitride layer is a carbonitride layer of iron, a surface layer consisting of carbonitride of group Va elements is formed, and if the nitride layer is a nitride layer of iron, a surface layer consisting of carbonitride of group Va elements is formed. A surface layer of elemental nitrides is formed. The maximum thickness of the surface layer that can be formed on the nitrided iron alloy material is:
It is the same as the layer thickness of the nitride layer, and therefore the thickness of the surface layer is defined by the nitriding process. Any method such as gas nitriding, gas soft nitriding, salt bath soft nitriding, glow discharge nitriding may be used as the nitriding method. It is desirable that the nitride concentration of the nitride layer be high, and that the nitride layer be thick.
Most preferably, the nitride layer thickness is in the range of 3 to 15 μm. If the nitride layer thickness is too shallow, the thickness of the Group Va element nitride or carbonitride layer formed will be thin, while if it is too deep, the toughness of the iron alloy material may decrease. After the iron alloy material is subjected to the above nitriding treatment, the iron alloy material and the material containing the Group Va element are allowed to coexist and then heat treated. This heat treatment diffuses Group Va elements onto the surface of the iron alloy material to form a surface layer made of its nitride or carbonitride. The material containing the Group Va element is one that supplies the Group Va element to be diffused into the surface of the iron alloy material, and a metal containing the element or a compound containing the element is used. Examples of the metal include metals of group Va elements and alloys such as ferrovanadium. Compounds containing the above elements include VCl ₃ ,
NbCl ₅ , K ₂ NbF ₇ , NbF ₅ , VF ₅ , K ₂ TaF ₇ ,
Examples include chlorides, fluorides, and oxides of V ₂ O ₅ , NaVO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ and the like. Therefore, although one or more of these materials containing Group Va elements are used, it is most practical to use a pure alloy. Further, the treatment agent has the function of acting as a medium for diffusion of the Group Va element to the surface of the iron alloy material. The treatment agent consists of one or more of alkali metal or alkaline earth metal chlorides, fluorides, borate fluorides, oxides, bromides, iodides, carbonates, nitrates, and borates. It consists of an alkali metal or alkaline earth metal compound, or one or both of an ammonium halide salt and a metal halide, and is appropriately selected and used depending on the heat treatment method. For example, the alkali metal or alkaline earth metal compounds include NaCl, CaCl ₂ , LiCl,
NaF, KF, LiF, KBF ₄ , Na ₂ CO ₃ , LiCO ₃ ,
Examples include KCO ₃ , NaNO ₃ , Na ₂ O, etc., and one or more of these are used. In addition, halogenated ammonium salts include NH ₄ Cl,
Examples of metal halides include NH ₄ Br, NH ₄ I, NH ₄ F, etc., and examples of metal halides include CrI ₂ , CrBr ₃ , TiF ₄ , VCl ₃ ,
Examples include TiBr ₄ and the like, and one or more of these are used. When using compounds containing Ti or Cr, group Va elements (V, Nb,
A surface layer containing Ti and Cr may be formed at the same time as Ta). In addition, when using a halide of a group Va element such as VCl ₃ or NbCl ₃ as a treatment agent, the above-mentioned group Va
It can also be used as a material containing group elements. Heat treatment methods include a molten salt immersion method, a molten salt electrolysis method, a powder method, and the like, depending on whether the processing agent is in a molten state or a solid state at the treatment temperature. Further, the powder method includes an embedding method, a paste method, a non-contact method, and a fluidized bed method. These will be explained below. The above-mentioned molten salt immersion method involves melting the treatment agent to form a molten bath, and immersing the material containing the Group Va element and the iron alloy material in the molten bath. The processing agent used in this method includes one or more of the above-mentioned processing agents, including chlorides, fluorides, borate fluorides, carbonates, nitrates, oxides, and borates of alkali metals or alkaline earth metals; Alternatively, a metal halide that melts and does not evaporate at a temperature below the heat treatment temperature is used. In addition, in order to improve the melting state,
It is desirable to use two or more of the above compounds, such as a combination of NaCl and CaCl ₂ . Furthermore, Al ₂ O ₃ ,
An oxide such as ZrO ₂ or a cyanide compound such as NaCN may be added. The reason why the material containing the Group Va element is immersed in the molten bath is to dissolve the Group Va element into the molten bath. A method for immersing a material containing a Group Va element is to add the material in the form of a powder (preferably 200 meshes or less) or a thin plate to the molten bath, or to use the material in the form of a rod or plate as an anode in the molten bath. There are methods such as immersing it in water and electrolyzing it to dissolve Group Va elements anodicly. The above anodic melting
When dissolving Group Va elements, the Group Va elements can dissolve quickly and improve work efficiency.
Moreover, it is advantageous in that material containing undissolved Group Va elements is not deposited on the bath bottom. In this case, as the cathode, a conductive substance inserted into the molten bath container or elsewhere is used. If the anode current density during anodic melting is increased, the infiltration rate will increase, but considering that infiltration occurs even without electrolysis, a relatively low current density is sufficient. Practically speaking, 0.1 to 0.8 A/cm ² is appropriate. The group Va elements dissolved in the bath diffuse into the surface of the nitride layer formed by the nitriding treatment of the iron alloy material, forming a nitride or carbonitride layer of the group Va element. Note that graphite, steel, or the like is used as the container for the molten bath, but steel is sufficient for practical use. In addition, the molten salt electrolysis method is a method in which a material containing a group Va element is immersed in a bath in which a treatment agent is melted.
An iron alloy material is immersed in the molten bath as a cathode in a state in which group elements are dissolved, and electrolytic treatment is performed. In this case, the bath container or a separately inserted conductive substance is used as the anode. As the treatment agent, the same one as in the molten salt immersion method described above is used, and the method of immersing the material containing the Group Va element in a bath containing the treatment agent and infusing the Group Va element can also be performed in the molten bath. A method similar to the salt immersion method may be used.
Further, electrolytic treatment can also be performed by immersing a material containing a Group Va element in a molten bath of a treatment agent as an anode and an iron alloy material as a cathode. In this case, there is an advantage that the anodic dissolution of the Group Va element and the formation of the surface layer can be performed simultaneously. In addition, the cathode current density for electrolytic treatment by immersing the iron alloy material is 2A/ ^cm2 or less, which is practically 0.8 to 0.05.
A/cm ² is appropriate. It should be noted that both the molten salt immersion method and the molten salt electrolysis method described above can be carried out either in the air or in a protective gas (N ₂ , Ar, etc.). Next, the powder method is a method in which the processing agent and a mixed powder of a material containing a Group Va element and an iron alloy material are made to coexist and heated. In the powder method, the following methods are available for coexisting a treatment agent, a mixed powder of a material containing a Group Va element, and an iron alloy material. In other words, there are two methods: embedding the iron alloy material in the mixed powder, which is generally called the embedding method, coating the surface of the iron alloy material with the mixed powder, which is generally called the paste method, and the non-contact method, which is generally called the paste method. There is a method in which the iron alloy material and the above-mentioned mixed powder are arranged in a non-contact state in a certain space, and a method is generally called a fluidized bed method in which the above-mentioned mixed powder is in a fluidized state to form a fluidized bed. This method involves inserting iron alloy material into the layer. The processing agent used in the above powder method is one or two of alkali metal or alkaline earth metal chlorides, fluorides, bromides, iodides, and boron fluorides.
It consists of one or both of a halogenated ammonium salt and a metal halide. In addition, among the powder methods, in the case of a fluidized bed, the metal halides mentioned above are those that sublimate or evaporate at a temperature below the heat treatment temperature (TiF ₄ , VF ₃ ,
TiBr ₄ etc.). This is because when metal halides that do not sublimate or evaporate at temperatures below the heat treatment temperature are used, the amount of gas generated from the processing agent that contributes to the diffusion of Group Va elements is reduced, and the resulting layer is thicker. This is because it becomes thinner. The mixing ratio of the treatment agent and the material containing the Group Va element is preferably within a range of 0.5 to 20% by weight (hereinafter referred to as % by weight) of the treatment agent relative to the material containing the Group Va element. If it is outside this range, the
It becomes difficult to form a surface layer consisting of nitrides or carbonitrides of group Va elements, and the formation of a continuous surface layer tends to become easier closer to the center of this range. Further, the particle size of the mixed powder of the treatment agent and the material containing the Group Va element may be such that it passes through a JIS No. 100 sieve when the embedding method, paste method, or non-contact method is performed.
Whether it is coarser or finer than this, there is no particular effect. Further, when carrying out the fluidized bed method, particles having a particle size in the range of 60 to 350 mesh are preferred. If the mesh is coarser than 60, a large amount of gas is required to fluidize the mixed powder, and the formation of a surface layer is difficult to proceed. On the other hand, if the powder is finer than 350 mesh, the mixed powder tends to float and becomes difficult to handle. Additives can be added to the mixed powder in addition to the treatment agent and the material containing the Group Va element. For example, when carrying out a paste method, an adhesive such as dextrin or water glass can be added. Additionally, some types of processing agents tend to solidify easily during heat treatment. In this case, inert powder such as alumina (Al ₂ O ₃ ) can be added. Furthermore, some combinations of materials containing Group Va elements and processing agents have poor surface layer formation effects. In such cases, a conventionally known halide as an activator can be added to enhance the effect of forming a surface layer. The amount of these additives added can be arbitrarily selected depending on the purpose. The embedding method, paste method, non-contact method, and fluidized bed method, which are specific examples of the powder methods described above, will be explained in detail below. In the burying method, a mixed powder of a treatment agent and a material containing Group Va elements is placed in a certain container, the iron alloy material as the treatment agent is buried in the powder, and the container is placed in a heating furnace or atmosphere furnace in the atmosphere. In this method, the iron alloy material is heated in the container. Note that a layer of inert powder such as alumina or metal powder such as iron-boron powder may be provided at the opening of the container to prevent outside air from entering. The paste method is a method in which an adhesive such as an aqueous dextrin solution, glycerin, water glass, ethylene glycol, and alcohol is added to a mixed powder to form a paste. A paste of this mixed powder is usually applied to the surface of the iron alloy material.
Coated with a thickness of mm or more. The paste-coated iron alloy material is usually placed in a container and heated in a heating furnace. The atmosphere may be air, but the paste coating layer can be made thinner in a non-oxidizing atmosphere. Furthermore, in this paste method, since the surface layer is formed only on the surface portion covered with the paste, it is possible to form the surface layer only on an arbitrary part of the surface portion of the iron alloy material. The non-contact method involves making the iron alloy material and the mixed powder coexist in a certain closed space. Specifically, the heat treatment is performed by placing the mixed powder near the opening of the container to prevent outside air from entering, and placing the iron alloy material at a position where it does not come into contact with the mixed powder in the container. This method has operational advantages because there is no contact between the iron alloy material and the mixed powder. The fluidized bed method uses a fluidized bed furnace.
A refractory material such as alumina is added to the mixed powder to prevent the mixed powder from forming a lump during fluidization, and the iron alloy material and the powder are placed in the furnace, and a fluidizing gas is introduced to form the powder. This creates a fluidized bed state. When the heat treatment is performed using this method, an extremely smooth surface layer can be obtained, and since the temperature distribution of the fluidized bed is uniform, a surface layer with a uniform thickness can be formed. As the fluidizing gas, an inert gas such as argon gas or a non-oxidizing gas such as nitrogen gas can be used. Further, it is desirable that the flow rate of the fluidizing gas be 50 cm/min or more in the fluidized bed to prevent powder from adhering to the surface layer.
The gas pressure is preferably in the range of 0.5 to 2 kg/cm ² for handling reasons. The heating temperature for the above heat treatment is 580°C or less. By processing at a temperature below 580℃, the base material of the iron alloy material becomes less susceptible to distortion. Further, it is desirable that the lower limit temperature is 450°C. When heat treated at a temperature lower than 450℃,
The formation rate of the surface layer consisting of nitrides or carbonitrides of Group Va elements is very slow. In practice, the high temperature tempering temperature of die steel and the tempering temperature of structural steel are
500-580℃ is desirable. The longer the heat treatment time, the more particles in the surface layer.
The content of group Va elements increases. Therefore, the treatment time is determined by the desired content of Group Va elements, and is selected within the range of 1 to 50 hours. Further, the practical thickness of the surface layer to be formed is about 3 to 15 μm. [Operation] Although the formation mechanism of the surface layer consisting of nitride or carbonitride of group Va elements according to the present invention is not clear, the present inventors have determined from microanalyzer analysis and the relationship between processing time and thickness that , it is thought to be as follows. Note that the following explanation is about the mechanism of forming a carbonitride layer of Group Va elements (m, n, o, and p below each represent a number). First, by nitriding the iron alloy material that is the material to be treated, nitrogen (N) supplied from the outside is used.
reacts with iron (Fe) and carbon (C) on the surface of the iron alloy material to form a nitride layer in the form of Fe _n (C,N) _o . A solid solution of nitrogen (in the form of Fe--N) is also formed directly below this nitride layer. Thereafter, by subjecting the iron alloy material to heat treatment, group Va elements (hereinafter referred to as M) from the outside are diffused into the nitride layer. This diffusion is Fe _n
This is a reaction in which Fe and M in (C,N) _o are substituted, and the nitride layer changes to (M,Fe) _p (C,N) _p . And Fe _n (C, N) _o layers are all (M, Fe) _p (C, N)
When it changes to _p , there is no further growth of the (M, Fe) _p (C, N) _p layer. In addition, in the (M, Fe) _p (C, N) _p layer, the surface has more M, and the closer to the base material, the more Fe
There tends to be a lot of Therefore, depending on the conditions, the amount of Fe at the surface may be extremely small, and it may be appropriate to express it as M _p (C, N) _p . Therefore, the thickness of the surface layer formed is the same as the thickness of the nitride layer formed by the initial nitriding process. Therefore, the maximum layer thickness of the surface layer can be determined by the conditions of the nitriding treatment. In addition, until all Fem(C,N) _o layers change to (M,Fe) _p (C,N) _p , (M, Fe) _p (C,
N) There is a surface layer consisting of two layers: _{a p} layer and a Fem(C,N) _o layer on the base metal side. The thickness of this surface layer is approximately equal to the thickness of the initial Fem(C,N) _o layer. Furthermore, in the case of forming a surface layer made of a nitride of a group Va element, the surface layer formation mechanism is the same as described above. This is because the method of the present invention performs heat treatment at a low temperature of 580°C or less, and thus the formation of a surface layer with such a treatment time-thickness relationship using such a mechanism has never been done before. unknown.
In the method of the present invention, as shown in FIG. 1 of Example 1, the surface layer thickness (Fem (C, N) _o layer thickness and (M ，
Fe) _p (total thickness of C, N) _p layer thickness) is not affected by heat treatment time. On the other hand, when heat treatment is performed at a high temperature such as 1000℃ (curve S1)
As the heat treatment time becomes longer, the surface layer thickness also increases as in general diffusion treatment. In addition, in practice, it is not necessary to change all the iron, carbon, and nitrogen nitride layers to (M, Fe) _p (C, N) _p layers. The two layers may coexist, or the entire layer may be changed to a (M, Fe) _p (C, N) _p layer. (The same applies when changing to ). [Effect of the invention] According to the present invention, iron/nitrogen or iron/carbon/
After forming the nitrogen nitride layer, the Group Va element diffusion treatment is performed at a low temperature of 580°C using the above-mentioned specific treatment agent.
An excellent surface layer consisting of nitride or carbonitride of Va group elements can be formed. Additionally, since the iron alloy material is heated at a low temperature, distortion is less likely to occur in the base material of the material. Furthermore, it has good operability due to low temperature treatment and does not require a large amount of energy. Furthermore, since the layer according to the present invention is formed by diffusion, it has excellent adhesion to the base material, unlike carbide and nitride layers formed by PVD, which do not undergo diffusion reactions, despite being processed at low temperatures. A dense surface layer can be formed. In addition, the nitride layer etc. formed by the present invention has a large amount of iron at the layer boundary and the thermal expansion coefficients of the layer and the base material are close to each other, so it has excellent thermal shock resistance and Peeling is less likely to occur even if thermal shock is applied, such as when used in aluminum. Moreover, the thickness of the formed layer is practically sufficient. In addition, the method of forming a surface layer consisting of a nitride or carbonitride of a group Va element according to the present invention is much more effective than the method of forming a carbonitride layer of a group Va element without nitriding. Layers can be formed in a short time. [Examples] Examples of the present invention will be described below. Note that % means weight %. Example 1 A JIS/SKH51 round bar specimen with a diameter of 6 mm and a length of 30 mm
Salt bath nitriding treatment was performed by immersing the sample in a salt bath at 570°C for 2 hours. Next, a heat-resistant steel container containing a mixture of 52 mol% CaCl ₂ and 48 mol% NaCl was heated in an electric furnace in the atmosphere to form a 550°C molten salt bath, and -100 mesh of ferrochloride was added to the bath. Vanadium (Fe-V,
JISI No.) powder was added at 20% to the above molten salt bath. The nitrided sample was immersed in this 550°C molten salt bath for 1 to 25 hours, then taken out and cooled in oil. After washing off the adhering bath agent, the cross section was polished and the thickness of the layer formed on the surface was measured by observing the cross-sectional structure. The results are shown in curve A in FIG. In this curve A, the thickness at 0 immersion time is the thickness of the nitride layer formed by the initial nitriding treatment, and is 1 hour.
The subsequent thickness is the total thickness of the nitride layer and the vanadium carbonitride layer (thickness of the entire surface layer) (the thickness of the carbonitride layer of V is shown in curve B). . The thickness of the total surface layer was almost the same for different treatment times and was approximately 4 μm. Note that FIG. 2 shows a micrograph (400x magnification) of the cross-sectional structure of the surface layer formed by immersion treatment for 8 hours. The surface layer is a layer with a smooth surface, and the boundary between the layer and the base material is complicated, making it a coating layer with excellent adhesion. Furthermore, analysis using an X-ray microanalyzer revealed that V, as well as N and C, were found in the surface layer as shown in FIG. According to the analysis results from the surface, about 45% V content was present. Furthermore, diffraction lines corresponding to VN were observed in X-ray diffraction. The surface layer formed from this is
It was confirmed that it was a vanadium carbonitride layer consisting of (V, Fe) (N, C). For comparison, a JIS/SKH51 specimen that had been nitrided using the same process as above was immersed in a molten salt bath heated to 1000°C and treated.
A vanadium carbonitride layer having a thickness shown by curve S1 in FIG. 1 was formed. As is clear from this comparative example, the layer thickness increases as the immersion time increases, but in the present invention, the total surface layer thickness does not increase even if the immersion time increases. Therefore, it has become clear that the formation mechanism of the carbonitride layer of the present invention is different from the formation mechanism of the high-temperature treatment of the comparative example. Example 2 A JIS/S45C specimen (diameter 7
mm, length 50 mm) was subjected to salt bath nitriding treatment. Next, a molten salt bath of CaCl ₂ +NaCl having the same composition as in Example 1 was prepared, and VCl ₃ powder (-320 mesh) was added in an amount of 15% based on the molten salt bath. The molten salt bath was heated to 500° C. and the specimen was immersed in the bath for 1 to 16 hours, and then taken out from the bath and cooled in oil. The surface layer formed had almost the same thickness and texture regardless of the immersion time. As an example, when we examined a sample that had been soaked for 4 hours, we found that a surface layer with a thickness of about 8 μm was formed, as shown in the micrograph of the cross-sectional structure of the surface layer (400x magnification) in Figure 4. Ta. X-ray diffraction and X shown in Figure 5
From the results of line microanalyzer analysis, it was confirmed that this surface layer was a vanadium carbonitride layer consisting of (V, Fe) (N, C). Example 3 Cylindrical shape with outer diameter φ10mm, inner diameter φ6mm, length 25mm
A JIS/S48C specimen was subjected to gas nitrocarburizing treatment at 570°C for 6 hours. Next, CaCl ₂ + with the same composition as in Example 1
A molten salt bath of NaCl was prepared, and in this bath, 3% Al ₂ O ₃ powder (-320 mesh) and 20% ferrovanadium alloy (JIS No. 1) were added to the molten salt bath.
Powder (-200 mesh) was added. The molten salt bath was heated to 550° C. and the specimens were immersed for 9 hours and 25 hours, respectively, and then taken out of the bath and cooled in oil. When the roundness of these two types of specimens was measured, they all had almost the same roundness, and both the upper and lower parts of the specimen were as small as about 5 μm. For comparison, the roundness of the specimen when immersed in a molten salt bath at a temperature of 850℃ (immersion time was 4 hours) was approximately
It was 20 μm, which was about 4 times larger than the specimen treated with the present invention. When the specimen treated according to the present invention (immersion temperature: 550°C, immersion time: 9 hours) was cut and the surface layer was observed, the formed surface layer was approximately 8 μm thick.
Analysis using an X-ray microanalyzer confirmed that the layer was a vanadium carbonitride layer consisting of (V, Fe) (N, C). Example 4 JIS/SKD11 specimen (diameter 6 mm, length 30 mm)
Ion nitriding treatment was performed at 550°C for 3 hours. Next, CaCl ₂ +NaCl with the same composition as in Example 1
A molten salt bath of
No.) was inserted, and current was applied for approximately 15 hours at an anode current density of 0.6 A/cm ² using this as an anode and the graphite container as a cathode. By this anodic dissolution treatment of Fe-V, Fe-V
Approximately 6% of the total amount of salt bath is calculated from the weight loss of the board.
% of vanadium was dissolved into the bath. The specimen was immersed in this molten salt bath at 550° C. for 9 hours, then taken out and cooled in oil. When the treated specimen was cut and examined using an X-ray microanalyzer, C was also found in the surface layer in addition to V and N, as shown in FIG. In addition, the X-ray diffraction results showed good agreement with the VN diffraction lines, confirming that the surface layer was a vanadium carbonitride layer. Example 5 A JIS/S45C specimen with a diameter of approximately 7 mm and a length of 50 mm was
Salt bath nitriding treatment was performed at 570°C for 1 hour. Next, a graphite container containing a mixture of 50 mol% KF and 50 mol% LiF was heated to 580°C in an electric furnace in the atmosphere to prepare a molten salt bath, and -100 mesh of Fe-V ( JIS No. 1) powder was added at 25% to the molten salt bath. The nitrided specimen was immersed in this 580° C. bath, and electrolysis was carried out by applying current at a cathode current density of 0.05 A/cm ² for 8 hours using this as a cathode and the graphite container as an anode. The specimen was taken out of the bath and cooled in oil, and the formed surface layer was analyzed using an X-ray microanalyzer, and it was confirmed that the surface layer was composed of (V, Fe) (C, N). Furthermore, analysis results from the surface confirmed that in addition to about 45% V, N and C were also present. Example 6 In the same manner as in Example 4, an industrial pure iron specimen (carbon content: 0.03% or less) having a diameter of 8 mm and a length of 35 mm was subjected to ion nitriding treatment. Next, CaCl ₂ + with the same composition as in Example 1
A molten salt bath of NaCl was prepared in a steel container, and -200 mesh Fe-V (JIS No. 1) powder was added to the bath in an amount of 30% based on the molten salt bath. The bath was heated to 580°C, and the specimen was immersed in the bath for 8 hours, and then taken out of the bath and cooled in oil. The formed surface layer has a layer thickness of about 12μ, which is the same as the thickness of the nitride layer when subjected to ion nitriding, as shown in the micrograph of the cross-sectional structure in Figure 7 (400x magnification).
It was m. Furthermore, as a result of X-ray microanalyzer analysis, approximately 70% of V, as well as N and C, were observed in the surface layer. In addition, from the results of X-ray diffraction, diffraction lines of V ₂ N and VN were observed, and the formed surface layer was (V,
It was confirmed that this was a vanadium carbonitride layer consisting of Fe) ₂ (C,N) + (V,Fe)(C,N). Example 7 A JIS/S45C specimen was subjected to salt bath nitriding treatment in the same manner as in Example 1. Then Li ₂ CO ₃ 45%, K ₂ CO ₃ 25%, Na ₂ CO ₃ 30%
A heat-resistant steel container containing the mixture was heated to 550°C in an atmospheric furnace to prepare a molten salt bath, and -100 mesh of pure niobium powder was added to this bath at 30% of the molten salt bath. did. After thoroughly stirring this bath, the specimen was kept immersed in this 550°C bath for 4 hours. The specimen was taken out of the bath and cooled in oil, and the formed surface layer was analyzed using an X-ray microanalyzer. As shown in FIG. 8, N and C in addition to Nb were observed in the surface layer. Further, when examined by X-ray diffraction, the diffraction lines matched well with those of NbN, and it was thus confirmed that the surface layer was composed of (Nb, Fe) (C, N). Example 8 A JIS/SK4 specimen with a diameter of 8 mm and a length of 30 mm was heated at 570°C.
Gas softening treatment was performed for 150 minutes. Next, -100 mesh of Fe-V90% and potassium borofluoride ( _KBF4 ) 10
The specimen was embedded in a mixed powder consisting of %. Furthermore, to prevent oxidation, the mixed powder was coated with -100 mesh ferroboron powder to a thickness of 3 to 4 mm.
The whole container was heated at 580°C for 16 hours in an atmospheric furnace.
The container was taken out of the furnace and cooled in air, and then a test piece was taken out from the powder. When the surface layer formed on the specimen was analyzed with an X-ray microanalyzer, V, N, and C were found in the surface layer, as shown in Figure 9, and the analysis results from the surface showed that about 20% of V was present in the surface layer. This layer was confirmed to be a vanadium carbonitride layer. Example 9 A JIS/S45C specimen with a diameter of 7 mm and a length of 30 mm was heated at 570°C.
Gas nitriding treatment was performed for 60 hours. Next, the sample was embedded in the same powder as in Example 8 and heated at 580°C for 16 hours. When the formed surface layer was analyzed with an X-ray microanalyzer, it was found that the surface layer was composed of V, N, and C, as shown in Figure 10, and approximately 40% of V was detected in the analysis results from the surface. It was confirmed that it was a carbonitride layer of vanadium. Example 10 Alumina (Al ₂ O ₃ , -200 mesh) 40%, Fe-
A mixed powder consisting of 55% V (-100 mesh) and 5% ammonium chloride (NH ₄ Cl, -80+100 mesh) was made into a paste using a solvent in which ethyl cellulose was dissolved in ethyl alcohol. After applying the above paste to a thickness of 3 to 5 mm on a JIS S45C specimen (diameter 20 mm, length 10 mm) that had been gas nitrided under the same conditions as in Example 9, it was placed in a stainless steel container and placed in an argon atmosphere. The mixture was heated at 580°C for 16 hours. When the formed surface layer was analyzed with an X-ray microanalyzer, it was confirmed that the surface layer was made of vanadium carbonitride. Example 11 A mixed powder consisting of 60% Al ₂ O ₃ (-80 mesh), 38.8% Fe-V (-100 mesh), and 1.2% VCl ₃ (-80 mesh) was placed in a fluidized bed furnace, and the lower part of the furnace Argon gas (flow rate in the furnace 200cm/min,
The mixed powder was brought into a fluid state under a pressure of 1.5 Kg/cm ² ) at the furnace inlet. A JIS SK4 rod (diameter 7 mm, length 50 mm) which had been nitrided in a salt bath in the same manner as in Example 1 was placed in this fluidized bed furnace and heated at 580° C. for 8 hours. When the formed surface layer was analyzed with an X-ray microanalyzer, it was found that the surface layer was composed of V, N, and C, as shown in Figure 11, and the surface layer was composed of about 30%
% V was detected, and the X-ray diffraction results showed that VN
Since it matched the diffraction line, the layer was (V, Fe)
It was confirmed that (C,N). Example 12 A JIS/SK4 specimen with a diameter of 7 mm and a length of 50 mm was heated at 570°C.
Salt bath nitriding treatment was carried out for 4 hours. Next, Al ₂ O ₃ (−80 mesh) 58.8%, Fe−Nb
(−100 mesh) 40%, NH ₄ Cl (−80 mesh)
A mixed powder consisting of 1.2% was placed in a fluidized bed furnace, and argon gas (flow rate 200cm/
The mixed powder was brought into a fluid state at a pressure of 1.5 kg/cm ² ). The above SK4 specimen was charged into this fluidized bed furnace,
Heat treatment was performed by holding at 580°C for 16 hours. When the formed surface layer was analyzed with an X-ray microanalyzer, it was found that the surface layer was composed of Nb, N, and C, as shown in Figure 12.
20% Nb was detected. According to the results of X-ray diffraction
Since it matched the NbN diffraction line, the layer was (Nb,
Fe) (C,N). Example 13 A plate-shaped JIS sheet with a length of 60 mm, a width of 20 mm, and a thickness of 10 mm.
The SKH51 specimen was subjected to salt bath nitriding treatment in the same manner as in Example 1. Next, a mixture of 52 mol% _CaCl2 and 48 mol% NaCl was placed in a heat-resistant steel container and heated to 570 mol% in an electric furnace in the atmosphere.
Prepare a molten salt bath by heating to
200 meshes of Fe-V (JIS No. 1) powder was added in an amount of 25% based on the total amount of the molten salt bath. After immersing the specimen in this 570°C bath for 8 hours, it was taken out and cooled in oil. When the formed surface layer was examined by X-ray diffraction, it was found that
Diffraction lines corresponding to VN were observed, and the surface layer was confirmed to be a vanadium carbonitride layer. Next, the above vanadium carbonitride coated specimen (Sample No.
Regarding C), spheroidized JIS/
A dry wear test was conducted using SCM21 as a mating material using an Okoshi type rapid wear tester under the conditions of a final load of 3.3 kg, a sliding distance of 600 m, and a sliding speed of 2 m/sec and 4.4 m/sec. For comparison, a JIS/SKH51 specimen (sample
No.S2) and SKH51 specimen with only nitriding treatment (sample
A wear test was also conducted for No.S3). The results of the above wear test are shown in the table. As is clear from the table, the surface layer formed according to the present invention is
It can be seen that it is less prone to wear compared to the comparative example.

[Table] JIS/SKH51 specimens were coated with a vanadium carbide (VC) layer approximately 4 μm thick by immersing them in a high-temperature molten salt bath at 100°C for 2 hours, or by chemical treatment at 850°C for 4 hours. Approximately 7μ by vapor phase deposition (CVD)
Abrasion tests were also conducted on JIS/SKH51 specimens coated with a titanium carbonitride layer made of Ti(C,N) with a thickness of m.
The amount of wear was almost the same as that of specimen C.
From this, the surface layer formed according to the present invention is
It can be seen that the surface layer is not inferior in terms of wear resistance and seizure resistance compared to surface layers formed by immersion in a molten salt bath at high temperatures or CVD.

[Brief explanation of drawings]

FIG. 1 is a diagram showing changes in the layer thickness of the surface layer formed in Example 1 with respect to immersion time, and FIG.
Figures 4 and 7 are examples 1, 2, and 6, respectively.
Micrographs (400x) showing the cross-sectional structure of the surface layer formed by the treatment of the present invention, Figs. 3, 5, 6, 8, 9, 10, 1
1 and 12 are Examples 1, 2, 4, and 1, respectively.
7, 8, 9, 11, and 12 are diagrams showing the results of X-ray microanalyzer analysis of the surface portion of the iron alloy material treated according to the present invention.

Claims (1)

[Claims] 1. After performing a nitriding treatment to form a nitride layer of iron/nitrogen or iron/carbon/nitrogen on the surface of an iron alloy material, the iron alloy material and a group Va element of the periodic table are treated. and one or more of alkali metal or alkaline earth metal chlorides, fluorides, borate fluorides, oxides, bromides, iodides, carbonates, nitrates, borates, or halogenated materials. By coexisting with a treatment agent consisting of one or both of ammonium salts and metal halides and heat-treating at 580°C or lower, Group Va elements are diffused onto the surface of the iron alloy material. A method for surface treatment of an iron alloy material, comprising forming a surface layer made of a nitride or carbonitride of a group Va element and having a layer thickness according to the conditions of the nitriding treatment. 2. The material containing the Group Va element is one or more of a metal of the Group Va element, an alloy of the Group Va element, and a compound containing the Group Va element as set forth in claim 1. Surface treatment method for iron alloy materials. 3. The heat treatment is carried out by immersing the material containing the Group Va element and the iron alloy material in a molten bath in which the treatment agent is melted.
A method for surface treatment of iron alloy materials as described in . 4. The iron alloy according to claim 1, wherein the heat treatment is performed by electrolytic treatment in which the treatment agent is melted and the iron alloy material is used as a cathode in a molten bath in which a material containing a Group Va element is immersed. Material surface treatment method. 5. The method for surface treatment of an iron alloy material according to claim 1, wherein the heat treatment is performed by embedding the iron alloy material in a mixed powder of the treatment agent and a material containing a Group Va element. 6. The heat treatment is performed in a state where a paste of mixed powder of the treatment agent and a material containing a Group Va element is applied to the iron alloy material.
A method for surface treatment of iron alloy materials as described in . 7. The heat treatment is performed by arranging the mixed powder of the treatment agent and the material containing the Group Va element and the iron alloy material in a fixed space in a non-contact state. Surface treatment method for alloy materials. 8. The heat treatment is carried out by making a mixed powder of the treatment agent and a material containing a Group Va element into a fluidized state and placing the iron alloy material therein. Surface treatment method.