JPH0447028B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention forms a nitride or carbonitride layer of zirconium (Zr) on the surface of iron alloy materials such as molds, jigs, tools, and machine parts. This invention relates to a surface treatment method. [Prior Art] When the surface of an iron alloy material is coated with a surface layer made of zirconium carbide, nitride, or carbonitride, various properties such as wear resistance, seizure resistance, oxidation resistance, and corrosion resistance of the iron alloy material are improved. It is well known that this can be improved. 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 of zirconium carbonitride is formed on the surface of an iron alloy material by plasma CVD (chemical vapor deposition) using a zirconium halide (e.g. , JP-A-55-2715, JP-A-55-164072).
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 of zirconium nitride or carbonitride on an iron alloy material that has excellent adhesion to the base 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 the iron alloy material and zirconium material and one or more of alkali metal or alkaline earth metal chlorides, borate fluorides, fluorides, oxides, bromides, iodides, carbonates, nitrates, borates, or ammonium halides. Alternatively, zirconium nitride or carbon may be formed on the surface of the iron alloy material by heat treatment at 700°C or lower in the presence of a treatment agent consisting of one or both of the metal halides and by diffusing zirconium onto the surface of the iron alloy material. This is a method for surface treatment of iron alloy materials, characterized by forming a surface layer made of nitride. In the present invention, the iron alloy material is a material to be treated on which a zirconium nitride or carbonitride layer 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. Furthermore, the greater the carbon content in the iron alloy material, the greater the amount of carbon in the formed zirconium carbonitride layer. 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 zirconium carbonitride layer. The nitriding process is to diffuse nitrogen N into the surface of the iron alloy material 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 zirconium material, zirconium diffuses into the nitride layer, and a substitution reaction occurs between zirconium and iron in the nitride layer. At this time, if the nitride layer is an iron carbonitride layer, a surface layer consisting of zirconium carbonitride is formed, and if the nitride layer is an iron nitride layer, a surface layer consisting of zirconium nitride is formed. A surface layer is formed. The maximum thickness of the surface layer that can be formed on the nitrided iron alloy material is the same as the layer thickness of the nitride layer, and therefore the thickness of the surface layer is determined by the nitriding treatment. Any method such as gas nitriding, gas soft nitriding, salt bath soft nitriding, glow discharge nitriding, etc. 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 zirconium 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 nitriding treatment described above, the iron alloy material and the zirconium material are allowed to coexist and heat treated. This heat treatment diffuses zirconium onto the surface of the iron alloy material to form a surface layer made of its nitride or carbonitride. The above-mentioned zirconium material supplies zirconium to be diffused onto the surface of the iron alloy material, and uses a metal, a zirconium compound, or the like containing this element. Examples of the metal include alloys such as zirconium metal and ferrozirconium.
The above zirconium compounds include ZrCl ₄ ,
Examples include chlorides, fluorides, and oxides such as Na ₂ ZrF ₆ and ZrO ₂ . Although one or more of these zirconium materials may be used, it is most practical to use ferrozirconium. Furthermore, the treatment agent has the function of acting as a medium for zirconium to diffuse onto 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, _KBF4 , _{Na2CO3 , LiCO3} ,
Examples include NaNO ₃ and Na ₂ O, and one or more of these may be used. In addition, halogenated ammonium salts include NH ₄ Cl, NH ₄ Br,
Examples of metal halides include NH ₄ I, NH ₄ F, etc., and examples of metal halides include CrI ₂ , CrBr ₃ , TiF ₄ , VCl ₃ , FeCl ₃ ,
Examples include TiBr ₄ and the like, and one or more of these are used. Note that when using a compound containing Ti or Cr, a surface layer containing Ti and Cr may be formed at the same time as zirconium (Zr). Furthermore, when a zirconium halide such as ZrCl ₄ is used as a treatment agent, it can also be used as the zirconium material. 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 molten salt immersion method is a method in which the treatment agent is melted to form a molten bath, and the zirconium material and the iron alloy material are immersed in the molten bath. The treatment agent used in this method is one of the alkali metal or alkaline earth metal chlorides, fluorides, borate fluorides, carbonates, nitrates, oxides, and borates.
One or more metal halides, or metal halides that melt and do not evaporate at temperatures below the heat treatment temperature, are used. In addition, in order to improve the melting state, NaCl
It is desirable to use two or more of the above compounds, such as a combination of CaCl 2 and CaCl ₂ . Furthermore, oxides such as Al ₂ O ₃ and ZrO ₂ and cyanide compounds such as NaCN may be added for the purpose of adjusting the viscosity of the molten bath. The reason for immersing the zirconium material in the molten bath is to dissolve zirconium into the molten bath. The zirconium material can be immersed by adding it to the molten bath in the form of a powder (preferably 200 mesh or less) or in the form of a thin plate, or by immersing the material in the form of a rod or plate in the molten bath as an anode. There are methods such as electrolysis and anodic dissolution of zirconium. Introducing zirconium by anodic melting is advantageous in that zirconium can be infused quickly and work efficiency can be improved, and undissolved zirconium material does not accumulate on the bath bottom. be. 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. In practical terms
0.1 to 0.8 A/cm ² is suitable. The zirconium dissolved in the bath diffuses onto the surface of the nitride layer formed by the nitriding treatment of the iron alloy material to form a zirconium nitride or carbonitride layer. 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 zirconium material is immersed in a bath in which a treatment agent is melted to infiltrate the zirconium, and an iron alloy material is immersed as a cathode in the molten bath to perform electrolytic treatment. It is. 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 may be used, and the means for infiltrating the zirconium by immersing the zirconium material in a bath containing the treatment agent may be the same as in the molten salt immersion method. . Further, electrolytic treatment can also be carried out by immersing the zirconium material as an anode and the iron alloy material as a cathode in a molten bath of a treatment agent. In this case, there is an advantage that the anodic melting of zirconium and the formation of the surface layer can be performed simultaneously. In addition, the cathode current density for electrolytic treatment by immersing iron alloy materials is 2A/ ^cm2 or less, and practically 0.8~
0.05A/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, a mixed powder of a zirconium material, and an iron alloy material are made to coexist and heated. In the powder method, the following methods are available for coexisting the treatment agent, the mixed powder of the zirconium material, and the 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. There is a method of inserting ferrous 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 halide mentioned above is one that sublimates or evaporates at a temperature below the heat treatment temperature (FeCl ₃ ,
VCl ₃ , 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 treatment agent that contributes to the diffusion of zirconium is reduced, resulting in a thinner layer. It is. The mixing ratio of the treatment agent and the zirconium material is preferably in a range of 0.5 to 20% by weight (hereinafter referred to as % by weight) of the treatment agent relative to the zirconium material. Outside this range, it becomes difficult to form a continuous surface layer consisting of zirconium nitride or carbonitride, and as you approach the center of this range, it tends to become easier to form a continuous surface layer. It is in. In addition, the particle size of the mixed powder of the processing agent and zirconium material may be such that it can pass through a JIS No. 100 sieve when implementing the embedding method, paste method, or non-contact method. As a result, there is no particular effect on whether it is coarse or fine.
Further, when carrying out a 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 above-mentioned processing agent and zirconium material. 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, an inert powder such as alumina Al ₂ O ₃ can be added. Furthermore, some combinations of zirconium materials 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 zirconium material is placed in a certain container, the iron alloy material to be treated is embedded in the powder, and the container is placed in a heating furnace or atmospheric furnace in the atmosphere, and the entire container is filled with iron. This is a method of heating alloy materials. 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, in which a refractory material such as alumina is added to the mixed powder to prevent the mixed powder from forming lumps during fluidization, and the above-mentioned iron alloy material is added to the mixed powder. The powder is placed in a furnace and fluidized gas is introduced to create a fluidized bed state in which the powder is fluidized. When heat-treated using this method, an extremely smooth surface layer can be obtained.
Furthermore, since the temperature distribution of the fluidized bed is uniform, a surface layer of 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. Gas pressure is 0.5 to 2 kg/
A range of cm ² is good. The heating temperature for the above heat treatment is 700°C or less. By processing at a temperature below 700°C, 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 of zirconium nitride or carbonitride is very slow. In practice, the high temperature tempering temperature of die steel and the tempering temperature of structural steel are
500-650℃ is desirable. As the heat treatment time increases, the zirconium content in the surface layer increases. Therefore, the treatment time is determined by the desired zirconium content 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] The formation mechanism of the surface layer made of zirconium nitride or carbonitride according to the present invention is not clear, but judging from microanalyzer analysis and the relationship between processing time and thickness, the inventors believe that the following It is thought that it is becoming like this. Note that the following explanation is about the mechanism of forming a zirconium carbonitride layer (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 reacts with iron Fe and carbon C on the surface of the iron alloy material.
A nitride layer is formed 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, zirconium (Zr) from the outside is diffused into the nitride layer. This diffusion is Fe of Fe _n (C,N) _o
This is a reaction in which Zr and Zr are substituted, and the nitride layer is formed by (Zr,
Fe) _p Changes to (C,N) _p . and Fe _n (C,N)
When all _o layers change to (Zr, Fe) _p (C, N) _p , there is no further growth of (Zr, Fe) _p (C, N) _p layers.
In addition, in the (Zr, Fe) _p (C, N) _p layer, there is a tendency that the closer to the surface there is more Zr, and the closer to the base material there is more Fe. 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 Zr _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 Fe _n (C, N) _o layers change to (Zr, Fe) _p (C, N) _p , (Zr, Fe) _p (C, N)
There is a surface layer consisting of two layers: _{a p} layer and a Fe _n (C, N) _o layer on the base metal side. The thickness of this surface layer is approximately equal to the thickness of the initial Fe _n (C,N) _o layer. Furthermore, when forming a surface layer made of zirconium nitride, 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 700°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 possible. unknown.
In the method of the present invention, as shown in FIG. 1 of Example 1, the surface layer thickness (Fe _n (C, N) _o layer thickness and ( Zr, Fe)
_p (C,N) (total thickness of _p layers) is not affected by heat treatment time. On the other hand, when heat treatment is performed at a high temperature such as 1000° C. (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 (Zr, Fe) _p (C, N) _p layers. It may be in a state where two layers coexist, or in a state in which the entire layer is changed to a (Zr, Fe) _p (C, N) _p layer (when changing an iron/nitrogen nitride layer to a surface layer consisting of a zirconium nitride). (The same applies to) [Effect of the invention] According to the present invention, iron/nitrogen or iron/carbon/
After forming the nitrogen nitride layer, zirconium is diffused using the above-mentioned specific treatment agent at a low temperature of 700°C or less. A surface layer 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. Moreover, the thickness of the formed layer is practically sufficient. Furthermore, the method of forming a surface layer made of zirconium nitride or carbonitride of the present invention can form a layer in a much shorter time than the method of forming a zirconium carbide layer without nitriding. Can be done. [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 3 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 molten salt bath at 550°C, and a -100 mesh film was added to the bath. Erozirconium (Fe-Zr
(Zr content 80%) powder against the above molten salt bath
% added. 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, polish the cross section,
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 immersion time 0 is the thickness of the nitride layer formed by the first nitriding treatment, and the thickness after 1 hour is the total thickness of the nitride layer and the zirconium carbonitride layer. (the thickness of the entire surface layer) (curve B shows the thickness of only the zirconium carbonitride layer). The thickness of the total surface layer was almost the same for different treatment times and was approximately 5 μm. Note that FIG. 2 shows a micrograph (400x magnification) of the cross-sectional structure of the surface layer formed by immersion treatment for 9 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, as shown in FIG. 3, analysis using an X-ray microanalyzer revealed that Zr as well as N and C were present in the surface layer. According to the analysis results from the surface, approximately 50% Zr content was present. Furthermore, diffraction lines corresponding to ZrN were observed in X-ray diffraction. The surface layer formed from this is
It was confirmed that it was a zirconium carbonitride layer consisting of (Zr, Fe) and (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 zirconium carbonitride layer with 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 ZrCl ₄ 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 6 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
The results of line microanalyzer analysis confirmed that this surface layer was a zirconium carbonitride layer consisting of (Zr, Fe) and (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 +NaCl with the same composition as in Example 1
A molten salt bath was prepared, and 3% Al ₂ O ₃ powder (-320 mesh) was added to the molten salt bath in this bath.
and 30% ferrozirconium alloy (Fe-Zr (Zr content 80%) powder (-200 mesh) was added.
This molten salt bath was heated to 550℃ and the above specimens were heated to 1, 9,
Each was immersed for 25 hours, then taken out from the bath and cooled in oil. When the roundness of these three 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 zirconium carbonitride layer consisting of (Zr, Fe) (N, C). Example 4 JIS/SKH51 specimen (diameter 6 mm, length 30 mm)
Ion nitriding treatment was performed at 550°C for 4 hours. Next, a molten salt bath of CaCl ₂ +NaCl with the same composition as in Example 1 was prepared in a graphite container, and a 40 mm x 35 mm x 4 mm zirconium metal plate was inserted in the center of this bath, and this was used as an anode and a graphite molten salt bath. Using the vessel as a cathode,
Current was applied at an anode current density of 0.7 A/cm ² for about 20 hours.
Due to this anodic dissolution treatment of zirconium, about 6% of zirconium was dissolved into the bath based on the total amount of the salt bath, calculated from the weight loss of the zirconium metal plate. The specimen was immersed in this melting circular bath at 550° C. for 8 hours, then taken out and cooled in oil. When the treated specimen was cut and examined using an X-ray microanalyzer, it was found that in addition to Zr and N, C was also found in the surface layer. Furthermore, since the X-ray diffraction results matched well with the diffraction lines of ZrN, it was confirmed that the surface layer was a zirconium 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 600°C in an electric furnace in the atmosphere to prepare a molten salt bath, and -100 meshes of Fe-Zr ( Zr content 80%) powder was added at 30% to the molten salt bath. The nitrided sample was immersed in this 600° 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 surface layer formed was analyzed using an X-ray microanalyzer, and it was confirmed that the surface layer was composed of (Zr, Fe) (C, N). In addition, the analysis results from the surface confirmed that in addition to approximately 65% Zr, 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 +NaCl with the same composition as in Example 1
A molten salt bath of -
200 meshes of Fe-Zr (80% Zr content) powder was added at 30% to the molten salt bath. The bath was heated to 600°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 approximately 12 μm, 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 6 (400x magnification).
It was hot. Further, as a result of X-ray microanalyzer analysis, approximately 50% Zr as well as N and C were found in the surface layer, and it was confirmed that this layer was a carbonitride layer of zirconium. Example 7 A JIS/SKD11 specimen was subjected to salt bath nitriding treatment in the same manner as in Example 1. Next, 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 520℃ in an atmospheric furnace to prepare a molten salt bath, and -200 mesh of zirconium metal powder was added to this bath at a rate of 30% of the molten salt bath. did. After thoroughly stirring this bath, the specimen was kept immersed in this 520°C bath for 5 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, and it was confirmed that the surface layer was composed of (Zr, Fe) (C, N). Further, the surface layer has a seventh
As shown in the micrograph (400x magnification) of the cross-sectional structure shown in the figure, the thickness was approximately 5 μm. This layer thickness was approximately the same as the thickness of the nitride layer from the initial salt bath nitriding treatment. Example 8 A JIS/S45C specimen with a diameter of 8 mm and a length of 30 mm was heated at 570°C.
Gas nitrocarburizing treatment was performed for 150 minutes. Next, the specimen was embedded in a -100 mesh mixed powder consisting of 90% Fe-Zr (Zr content 70%) and 10% potassium borofluoride (KBF ₄ ), which was placed in a stainless steel container. 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 to 600℃ in an atmospheric furnace.
Heated for 16 hours. 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 using an X-ray microanalyzer, it was found that Zr, N,
C was recognized, and the analysis result from the surface shows that it is approximately 20%
This layer was confirmed to be a zirconium carbonitride layer. Example 9 Alumina (AL ₂ O ₃ -200 mesh) 40%, Fe-
Zr (Zr content 70%) (-100 mesh) 55%, ammonium chloride (NH ₄ Cl, -80 + 100 mesh) 5
% was made into a paste using a solvent in which ethyl cellulose was dissolved in ethyl alcohol. 3 on a JIS/SK4 specimen (diameter 20 mm, length 10 mm) treated with gas nitrocarburizing at 570℃ for 60 hours.
After applying the above paste to a thickness of ~5 mm, it was placed in a stainless steel container and placed in an argon atmosphere.
Heated at 600°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 zirconium carbonitride. Example 10 Al ₂ O ₃ (-80 mesh) 60%, Fe-Zr (Zr content
A mixed powder consisting of 38.8% (70%) (-100 mesh) and 1.2% NH ₄ Cl (-80 mesh) was placed in a fluidized bed furnace, and argon gas was introduced from the bottom of the furnace (flow rate in the furnace was 200 cm/min). , pressure at furnace inlet 1.5Kg/
cm ² ) to bring the mixed powder into a fluid state. In this fluidized bed furnace, salt bath nitriding treatment was carried out in the same manner as in Example 1.
JIS/SK4 rod (diameter 7mm, length 50mm) charged 600
Heat treatment was performed at ℃ for 16 hours. When the formed surface layer was analyzed using an X-ray microanalyzer, it was found that the surface layer was
It is composed of Zr, N, and C, and surface analysis shows that it is approximately 20
% of Zr was detected, and the X-ray diffraction results showed that ZrN
Since it matched the diffraction line, the layer was (Zr, Fe)
It was confirmed that (C,N). Example 11 570 JIS/SKD61 specimens with a diameter of 7 mm and a length of 50 mm
Salt bath nitriding treatment was performed at ℃ for 4 hours. Next, Al ₂ O ₃ (-80 mesh) 58.8%, Fe-Zr
(Zr content 70%) (-100 mesh) 40%, _NH4Cl
(-80 mesh) A mixed powder consisting of 1.2% was placed in a fluidized bed furnace, and the mixed powder was brought into a fluidized state with argon gas (flow rate 200 cm/min, pressure 1.5 Kg/cm ² ) introduced from the bottom of the furnace. The above inside this fluidized bed furnace
A SKD61 specimen was charged and heated at 600°C for 16 hours. When the formed surface layer was analyzed using an X-ray microanalyzer, the surface layer was composed of Zr, N, and C, and approximately 20% Zr was detected in the analysis from the surface. Since the X-ray diffraction results matched the ZrN diffraction lines, it was confirmed that the layer was (Zr, Fe) (CON). Example 12 A JIS/SKH51 specimen with a diameter of 6.5 mm and a length of 40 mm 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 550 mol% in an electric furnace in the atmosphere.
Prepare a molten salt bath by heating to
200 meshes of Fe-Zr (80% Zr content) powder was added at 25% to the total amount of the molten salt bath. After immersing the specimen in this 550°C bath for 8 hours, it was taken out and cooled in oil. When the formed surface layer was examined by X-ray diffraction,
Diffraction lines corresponding to ZrN were observed, and the surface layer was confirmed to be a zirconium carbonitride layer. Next, the above zirconium carbonitride coated specimen (sample
Regarding No.C), gas carburized and quenched JIS
Dry test using SCM415 as a mating material using a Fababilly tester, load 400g, rotation speed 300rpm, friction speed 0.1
A friction test was conducted under the conditions of m/sec. For comparison, friction tests were also conducted on a JIS SKH51 specimen (sample No. S2) that had not been subjected to the above-mentioned nitriding treatment or heat treatment, and an SKH51 specimen that had been subjected to only nitriding treatment (sample No. S3). The results of the above friction test are shown in the table. Also, the sample
Seizure scratches were clearly generated in both Nos. S2 and S3, whereas only small damage was observed in sample No. C. This shows that the surface layer formed according to the present invention is excellent in wear resistance and seizure resistance. 【table】

[Brief explanation of the drawing]

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.
4, 6, and 7 are micrographs (400°
3), FIG. 5, and FIG. 8 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 in Examples 1, 2, and 10, respectively.

Claims (1)

[Claims] 1. After performing nitriding treatment to form an iron/nitrogen or iron/carbon/nitrogen nitride layer on the surface of the iron alloy material, the iron alloy material, the zirconium material, and the alkali metal or alkali Earth metal chlorides, fluorides, boron fluorides, oxides, bromides, iodides,
The above-mentioned zirconium is heated at 700°C or lower in the presence of a treatment agent consisting of one or more of carbonates, nitrates, borates, ammonium halides, and/or metal halides. A method for surface treatment of an iron alloy material, which comprises forming a surface layer of zirconium nitride or carbonitride on the surface of the iron alloy material by diffusing it onto the surface of the iron alloy material. 2 The above zirconium material is one of zirconium metal, zirconium alloy, and zirconium compound.
The method for surface treatment of an iron alloy material according to claim 1, which comprises one or more types. 3. The method for surface treatment of an iron alloy material according to claim 1, wherein the heat treatment is performed by immersing the zirconium material and the iron alloy material in a molten bath containing the treatment agent. 4. The method for surface treatment of an iron alloy material 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 the zirconium material is immersed. . 5. The method of 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 the zirconium material. 6. The method for surface treatment of an iron alloy material according to claim 1, wherein the heat treatment is performed in a state where a paste of mixed powder of the treatment agent and the zirconium material is applied to the iron alloy material. 7. The surface of the iron alloy material according to claim 1, wherein the heat treatment is performed by placing the mixed powder of the treatment agent and the zirconium material and the iron alloy material in a fixed space in a non-contact state. Processing method. 8. The method of surface treatment of an iron alloy material according to claim 1, wherein the heat treatment is carried out by bringing the mixed powder of the treatment agent and the zirconium material into a fluidized state and placing the iron alloy material therein.