JPS63125654A - Surface treatment of iron or iron alloy material - Google Patents

Abstract

PURPOSE:To form a carbonitride layer of Cr having excellent resistance to wear, seizure, corrosion, oxidation, etc., on the surface of iron and steel materials by incorporating Cr into a fused salt bath of the cyanide salt, etc., of alkali metals and alkaline earth metals, then immersing the iron and steel materials into said bath and heating the same to a specific temp. CONSTITUTION:Metal Cr, iron-chromium alloy, Cr2O3, etc., are added and dissolved in the state of fine powder into the fused salt prepd. by adding 1 or >=2 kinds of the cyanide salt and cyanate of the alkali metals or alkaline earth metals or further 1 or >=2 kinds among the chloride, fluoride, borofluoride, oxide, boride, iodide, carbonate, nitrate, and borate of the alkali metals or alkaline earth metals. Such fused salt bath is heated to <=650 deg.C and the iron and steel members consisting of carbon steel, alloy steel, cast iron, sintered alloy, etc., are immersed therein. An electrolytic treatment is otherwise executed with the iron and steel members as a cathode and the Cr-contg. material as an anode to form the hard carbonitride layer of chromium having various excellent characteristics on the surface of the iron and steel members.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for forming a carbonitride layer of chromium (Cr) on the surface of iron or iron alloy materials such as molds, jigs, tools, and machine parts. This relates to a processing method.

[Conventional technology]

When a surface layer made of chromium carbide, nitride, or carbonitride of chromium is coated on the surface of iron or iron alloy material (hereinafter referred to as the treated material), the wear resistance, seizure resistance, and oxidation resistance of the treated material are improved. It is well known that various properties such as corrosion resistance are improved. Many proposals have been made in recent years regarding methods of coating this surface layer. For example, a method of forming a chromium carbide layer by immersing an iron alloy material in a chloride-based molten salt bath (JP-A-57-200555, JP-A-58
-197264), or a method in which a surface layer consisting of chromium carbonitride is formed by chromizing after nitriding the iron alloy material (Japanese Patent Publication No. 42-24697, jl, S , P, 424215
Publication No. 1).

However, in all of the above methods, heat treatment is performed at a temperature higher than approximately 700°C, which is the AC and transformation point of iron, which causes distortion in the base material of the iron alloy material, resulting in the formation of complex-shaped materials. There is a risk of it breaking. There are also other problems, such as the high heat and poor working environment.

On the other hand, methods for forming a surface layer containing chromium at temperatures below 700°C include CVD (Chemical Vapor Deposition) (PVI), which uses chromium halides, etc.
Physical vapor deposition (physical vapor deposition) and other methods have been proposed. But in these methods.

It is difficult to obtain a formed surface layer with good throwing power and adhesion. Furthermore, the processing steps are complicated and the equipment is expensive. Furthermore, it is inefficient because it must be carried out in hydrogen or reduced pressure.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned conventional problems and provides excellent adhesion to the base material of iron alloy materials by efficient heat treatment at low temperatures using extremely simple equipment, without causing distortion to the base material. The object of the present invention is to provide a method for forming a surface layer of chromium carbonitride.

[Means for solving problems]

The first invention coexists an iron or iron alloy material, a chromium-containing material, and a treatment agent consisting of one or more of cyanide salts and cyanates of alkali metals or alkaline earth metals. At least, a surface layer consisting of chromium carbonitride is formed on the surface of the iron or iron alloy material by heat treatment at 650° C. or higher to diffuse chromium, nitrogen and carbon onto the surface of the iron or iron alloy material. This is a method for surface treatment of iron or iron alloy materials.

The second invention provides an iron or iron alloy material, a material containing chromium, one or more of cyanide salts and cyanates of an alkali metal or alkaline earth metal, and an alkali metal or alkaline earth metal. Metal chlorides, boron fluorides,
fluoride, oxide, bromide, iodide, carbonate, nitrate,
By coexisting with a treatment agent consisting of one or more types of borates and heat-treating at 650°C or less to diffuse chromium, nitrogen, and carbon onto the surface of the iron or iron alloy material, Alternatively, there is provided a surface treatment method for iron or iron alloy material, characterized in that a surface layer made of chromium carbonitride is formed on the surface of iron alloy material.

In the present invention, the iron or iron alloy material is the material to be treated on which a chromium carbonitride layer is formed.

The iron or iron alloy material includes carbon.

For example, carbon steel 1 alloy steel, cast iron, sintered alloy, etc. may be used, or it may be a material that does not contain carbon at all, such as pure iron. Also, it does not need to contain nitrogen.

It's okay if it's included.

In the present invention, - the heat treatment in which the above-mentioned material to be treated, a material containing chromium, and a treatment agent are made to coexist and heated is performed by diffusing chromium, nitrogen, and carbon onto the surface of the material to be treated, thereby removing chromium. This forms a surface layer made of carbonitride.

Note that, as described in the following operations, the surface layer made of chromium carbonitride that is formed is a layer made of carbonitride whose main component is chromium. Also.

Directly below the chromium carbonitride layer, a solid solution layer (diffusion layer) of nitrogen and carbon in iron is formed.

- The material containing chromium (Cr) is one that supplies chromium to be diffused onto the surface of the material to be treated.

A metal containing chromium or a chromium compound is used. Such metals include pure chromium and ferrochrome (Fe-Cr).
Examples include alloys such as The above compounds include CrC
l2. Chlorides such as CrFa, Crz03+ and 2Cr03.

Examples include fluorides and oxides. Therefore, although one or two of these chromium-containing materials are used, it is most practical to use pure chromium.

Furthermore, the treatment agent has the function of supplying nitrogen and carbon to be diffused onto the surface of the material to be treated and serving as a medium for chromium to diffuse onto the surface of the material to be treated.

The treatment agent may be one or more of cyanide salts and cyanates of alkali metals or alkaline earth metals (hereinafter referred to as the first treatment agent), or the first treatment agent. and one or more of the following: chlorides, fluorides, borate fluorides, oxides, bromides, iodides, carbonates, nitrates, and borates of alkali metals or alkaline earth metals.

This may be used as a second treatment agent). Note that the first treatment agent supplies nitrogen and carbon that diffuse to the surface of the iron alloy material. In addition, the second processing agent has the function of adjusting the melting point, viscosity, amount of evaporation, etc., and increasing the stability of the processing.
It is appropriately selected and used depending on the heat treatment method.

For example, as the first treatment agent, NaCN, KCN, N
Examples include aCN0°KCNO, and one or more of these may be used.

In addition, as a second treatment agent, Ll:, NaCl, KCI,
CaCIz.

LiCl, NaF, KF, LiF+KBFa
, NazCOi+ LiCO31KzcOff+N
a N O21K N 031)- i B r +
Examples include K I + N a 20, and one or more of these are used.

The mixing ratio of the processing agent and the material containing chromium is 0.5 to 30% by weight relative to the material containing chromium.

% by weight) is preferable. If it is outside this range, it will be difficult to form a continuous surface layer, and if it approaches the center of this range, it will tend to be easier to form a continuous surface layer.

Heat treatment methods include molten salt immersion method, molten salt electrolysis method,
There are paste methods etc.

These will be explained below.

In the 1-molten salt immersion method, the treatment agent is melted to form a molten salt bath, and the chromium-containing material and the material to be treated are immersed in the molten salt bath.

The reason for immersing the +,1 rice grains containing chromium 1 in the molten salt bath is to dissolve chromium into the molten salt bath.

Chromium can be infused by adding the material to a molten bath in the form of a powder (preferably 200 mS or less) or in the form of a thin plate, or by immersing the material in the form of a rod or plate in a molten bath as an anode and electrolyzing it. There are methods such as anodic dissolution of chromium. The rate at which chromium dissolves into the molten salt from materials containing chromium differs depending on the type and size of the chromium-containing material used. It is necessary to maintain (ripen) the product at a temperature around that level. When chromium is injected by the above-mentioned anodic melting, the chromium infiltrates quickly and improves work efficiency, and furthermore, material containing undissolved chromium does not accumulate on the bath bottom. It's advantageous. In this case, as the cathode, a conductive substance inserted into a molten salt 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. Practical” 2 is 0.
1 to 0.8 A/ct is suitable.

The chromium dissolved in the bath diffuses onto the surface of the material to be treated together with nitrogen and carbon supplied from the treatment agent to form a surface layer consisting of chromium carbonitride.

The container for the molten salt bath is graphite or titanium.

Steel is used, but steel is sufficient for practical purposes.

In addition, the molten salt electrolysis method is a method in which a material containing chromium is immersed in a bath in which a treatment agent is melted to infiltrate the chromium, and the material to be treated is immersed as a cathode in the molten salt bath, and electrolytic treatment is performed. This is what we do. In this case, the bath container or a separately inserted conductive substance is used as the anode.

A method similar to the molten salt immersion method described above may be used to dissolve the chromium by immersing the chromium-containing material in a bath containing a molten treatment agent. In addition, a material containing chromium is added to the molten salt bath of the treatment agent as an anode.
Electrolytic treatment can also be performed by immersing the material to be treated as a cathode. In this case, there is an advantage that the anodic melting of chromium and the formation of the surface layer can be performed simultaneously.

Further, the cathode current density at which the material to be treated is immersed and subjected to electrolytic treatment is 2 A/cnl or less, and 0.05 to 1° OA/cd is suitable for practical use.

Note 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 (Nz, Ar, etc.).

The paste method is a process in which a mixed powder of the treatment agent and a material containing chromium, or a treatment agent into which chromium has been infused as described above, is cooled and solidified and then ground into a paste form and coated on the material to be treated. It is then heated.

In order to form the powder into a paste, an adhesive such as an aqueous dextrin solution, glycerin, water glass, ethylene glycol, or alcohol is added. This powder paste is usually coated on the surface of the material to be treated to a thickness of IN 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 material to be treated.

Further, the particle size of this powder may be such that it can pass through a JIS Naloo sieve. Whether it is coarser or finer than this, there is no particular effect.

The heating temperature of the above heat treatment is 650° C. or lower. By processing in a temperature range of 650° C. or lower, the base material of the material to be processed is less susceptible to distortion.

Further, it is desirable that the lower limit temperature is 450°C. When heat treatment is performed at a temperature lower than 450° C., the rate of formation of the second surface layer is very slow. Practically speaking, the high temperature tempering temperature for die steel is preferably 500 to 650°C, which is the tempering temperature for structural steel.

As the treatment time of the heat treatment increases, the thickness of the surface layer increases, and when the treatment takes a short time, the chromium content in the surface layer increases.

Therefore, the treatment time is determined by the desired thickness or chromium content of the surface layer, and is selected within the range of 1 to 50 hours.

Further, the practical thickness of the surface layer to be formed is about 1 to 10 μm. If the thickness exceeds this, there is a risk that the toughness of the material to be treated will decrease or the layers will peel off.

[Effect]

The formation mechanism of the surface layer made of chromium carbonitride according to the present invention is not clear, but as judged by the present inventors from X-ray diffraction, microanalyzer analysis, and the relationship between processing time and thickness, it is as follows. (m below)
, n, o, and p each represent a number).

First, nitrogen (N) and carbon (C) diffuse into the iron or iron alloy material to be treated from the outside and react with iron (Fe) on the surface of the treated material to form Fe, (CI N). A nitride layer is formed in the form of n. Note that carbon (C) is contained in the material to be treated.
Or, if nitrogen (N) is included, this carbon or nitrogen (N) is also included in Fe, (C,N), etc. Also,
Immediately below this nitride layer, a solid solution of nitrogen and carbon to iron (in the form of Fe--N--C) is also formed. These reactions proceed from the surface to the interior.

Immediately thereafter, chromium (Cr) is added to the nitride layer from the outside.
A reaction begins in which the ions diffuse, and the above two reactions proceed in parallel. This diffusion is F e +n (C+ N ),,
This is a reaction in which Fe and Cr are substituted, and the nitride layer is formed by (C
r, Fe). (C9N)p, and the reaction progresses gradually from the surface to the inside. In addition, (Cr, Fe
). In the (C,N)p layer, the surface tends to have more Cr, and the closer it is to the base material, the more Fe. Therefore, depending on the conditions, the amount of Fe on the surface may be extremely small, and Cro (C
+ N) In some cases, it is appropriate to express it as p.

Furthermore, in addition to the above-mentioned reaction, a reaction in which Cr and N or a combination of Cr, N, and C are directly precipitated on the surface of the material to be treated may also be occurring at the same time.

This (Cr, Fe). The thickness, thickness ratio, and chemical composition of the (C5N) p layer and the solid solution layer of iron, nitrogen, and carbon are determined by the type of base material, treatment temperature for 1 hour, and type of treatment agent.

It is possible to adjust by adjusting the mixing ratio.

Note that the present inventors have previously proposed a surface treatment method for a workpiece made of an iron alloy material, which is characterized by forming a surface layer made of chromium nitride or carbonitride on the surface of the workpiece. He made an invention related to law and filed an application (Japanese Patent Application No. 431556/1983).

After applying nitriding treatment to form an iron-nitrogen or iron-carbon-nitrogen compound layer on the surface of the treated material, the treatment is performed using +4 to be treated, a material containing chromium, and an alkali metal or alkaline earth metal. Chloride, fluoride.

Bow fluoride, oxide, bromide, iodide, carbonate.

700° with a treatment agent consisting of one or more of nitrates and borates, one or both of ammonium halides and metal halides.
A surface layer made of chromium nitride or carbonitride is formed on the surface of the material to be treated by heat treatment at a temperature of C or less and diffusing chromium into the compound layer formed by the nitriding treatment. This was a surface treatment method (hereinafter referred to as the two-time treatment method).

In the present invention and the previous two-step processing method, a salt bath method or a paste method is used at a low temperature where distortion due to heat is less likely to occur.

Although they are similar in that a surface layer made of chromium carbonitride is formed on the surface of the material to be treated, they differ greatly in the following points.

(A) Mechanism of carbonitride layer formation IA- In the two-step treatment method, iron-nitrogen and iron-carbon-nitrogen compound layers are formed in the first treatment, and chromium and iron-carbon-nitrogen compound layers are formed in the 22nd treatment. A chromium nitride layer and a carbonitride layer are formed by the substitution reaction of chromium with iron. Therefore, the maximum thickness of the surface layer that can be formed on the nitrided material is:
It is the same as the thickness of the iron-nitrogen and iron-carbon-nitrogen compound layers formed in the first treatment, and therefore the thickness of the surface layer is defined by the first nitriding treatment.

On the other hand, in the present invention, as shown in the second embodiment,
The chromium carbonitride layer tends to become thicker in proportion to the square of the processing time.

(B) Characteristics of treated materials Although the hardness, abrasion resistance, and burning resistance of the formed layers are at the same level, there is a large difference in the toughness of the treated materials.

In general nitriding treatment, in order to prevent a decrease in the toughness of the base metal,
In nine cases, the treatment was performed so as not to form a compound layer on the surface. On the other hand, in the treatment method No. 2 filed earlier, it is necessary to form a thick compound layer, and accordingly, a thick iron/nitrogen solid solution layer is also formed. Even in the results of the analysis using the X-ray microanalyzer shown in the examples,
It is clear that a large amount of nitrogen is solidly dissolved in the base metal, and these have a negative effect on the toughness of the base metal.

In the treatment according to the present invention, the amount of solid solution of nitrogen in the base material is extremely small, and the solid solution layer of iron, nitrogen and carbon is also thin, as seen in the later examples, compared to the case of the two-time treatment method. Therefore, it is considered that the material to be treated according to the present invention has higher toughness than the material to be treated by the two-time treatment method.

(C) Processing Efficiency In contrast to the two-step processing method, which requires two different treatments, the two-step processing method of the present invention allows the formation of a layer in one processing. Therefore, in addition to high processing efficiency, it has the advantage of requiring less equipment.

〔Effect of the invention〕

According to the present invention, since the diffusion treatment of Kuro J1 is performed at a low temperature of 650° C. or lower using the above-mentioned specific treatment agent,
At low temperatures, excellent surface layers of chromium carbonitrides can be formed on iron or iron alloy materials.

Additionally, since the iron or iron alloy material is heated at low temperatures, distortion is less likely to occur in the base 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,
PVD with no diffusion reaction despite processing at low temperatures
Unlike the case of carbide and nitride layers, it has excellent adhesion to the base material and can form a dense surface layer. Moreover, the thickness of the formed layer is practically sufficient.

〔Example〕

Two aspects of the present invention will be described in detail below.

Example 1 NaCN0 53 wt%, KCl12 wt% and Ca
A heat-resistant steel container containing a mixture of C]z and 35 wt% is heated in an electric furnace in the atmosphere to form a 570°C molten salt bath, and 1100 mesosh of pure chromium powder is added to the molten salt bath. 15 wt% was added. This molten salt bath has a diameter of 6 mm.
Iris 1. 1 JIS-3KH51 round bar test piece with a length of 20
After soaking for ~50 hours, it was taken out and air cooled. After washing and removing the adhesion solvent, the cross section was polished and the cross-section &l weave was observed. - As an example, FIG. 1 shows a micrograph (magnification: 400 times) of a cross-sectional a-woven surface layer formed by immersion treatment for 8 hours. The surface layer is a smooth surface layer and consists of one layer. The cross section of this sample was analyzed using an X-ray microanalyzer, and as shown in FIG. 2, N and C were found in the surface layer along with Cr and Fe. In addition, a solid solution layer of N and C in iron was formed just below the surface layer, but the amount of solid solution of N was extremely small (
The same applies to other examples). According to the analysis results from the surface, approximately 60% Cr content was present, and furthermore, diffraction lines corresponding to CrN, CrJ, and Fe5C were observed in X-ray diffraction. The surface layer formed by this is CrN, C
Chromium consisting of a mixed layer mainly composed of r2N and Fe5C.
It was confirmed that it was a carbonitride layer of iron. FIG. 3 shows the results of measuring the thickness of the layer formed on one surface by observing the cross-sectional structures of test pieces treated with four different immersion times ranging from 1 to 50 hours. The layer thickness is 2 times the processing time.
There was a tendency to increase almost in proportion to the

In addition, in order to examine the adhesion of the layers formed in the two examples,
Using a Rockwell hardness meter, press the indenter under Rockwell C scale hardness measurement conditions.

Changes appearing around the indentations were observed. As a result, in the layer formed by one layer, tensile stress was applied to the two layers due to the swelling of the base material around the indentation, and about 10 cracks were generated in a radial pattern, but no peeling of one layer was observed. It showed good adhesion. On the other hand, for comparison, a similar test was conducted on a Tin layer formed by ion blating, and the results showed that the layer around one layer was completely peeled off in an annular shape.

Example 2 NaCN0 57 wt%, NaCN13 wt% and N
aC1) 9wt% and CaC]. A graphite container containing a mixture of 21 wt% was heated to 550° in an electric furnace in the atmosphere.
A molten salt bath of C was formed, and CrCh powder (
-320 MSO) at 15 wt% in the above molten salt bath.
A J with a diameter of 3 mm and a length of 20 mm was added to this molten salt bath.
After immersing the IS-S 4.5C round bar test piece for 4 hours, it was taken out and cooled in the air.

A micrograph (400x magnification) of the cross-sectional structure of the test piece is shown in the fourth photo.
As shown in the figure. The layer formed on the surface had a single layer structure with a smooth surface, similar to the case of Example 1.

From the results of X-ray diffraction and XvA microanalyzer analysis shown in FIG. 5, as in Example 1, CrN.

It was confirmed that the layer was a chromium-iron carbonitride layer consisting of a mixed layer mainly composed of Cr z N + Fe 3 C.

In addition, the adhesion evaluation using a Rockwell hardness test showed the same cracking pattern as in Example 1, and it was determined that the layer had good adhesion.

Example 3 KCl42 wt%, NaCN38 wt% and KF14
A heat-resistant steel container containing a mixture of 5 wt% and 5 wt% of LiF is heated in an electric furnace in the atmosphere to form a 550°C molten salt bath, and 1100 mesh of pure chromium powder is added to the bath. 15 wt% was added to the molten salt bath. JIS/5KD with a diameter of 3++ m and a length of 151) was added to this molten salt bath.
II After soaking the round bar test piece for 8 hours.

It was taken out and air cooled.

After removing the treatment agent adhering to the specimen, examination using X-ray diffraction and an X-ray microanalyzer revealed that chromium, which consists of a mixed layer mainly composed of CrN, CrJ, Fe, and C, was formed on the two surfaces as in the other examples. It was confirmed that an iron carbonitride layer was formed.

Example 4 A heat-resistant container containing a mixture of NaCNO46wt%, NaCl19wt%, Na2cO325wt%, and LiBr1Owt% was heated in an electric furnace in the atmosphere to form a 600°C molten salt bath, and further 1100 in this bath
15 wt % of mesh Fe-Cr powder was added.

This molten salt bath has a diameter of 61 m and a length of 201) JIS 5
After soaking the KH51 round bar test piece for 16 hours, it was taken out and air cooled.

After the treatment, it was cut and examined using X-ray diffraction and an X-ray microanalyzer, and as a result, it was confirmed that a carbonitride layer of 1 com-iron was formed on one surface, as in the other Examples.

23-Example 5 NaCNO46wt% and NaC1)9wt% and Na
A heat-resistant steel container containing a mixture of zC(1+ 25wt% and K1) 0wt% was heated in an electric furnace in the atmosphere to 60%
A 0"C molten salt bath was formed, and 5 wt% of 1100 mesh chromium fluoride powder (CrF6) was added to this bath. A JI with a diameter of 8 fins and a length of 15 cm was added to this molten salt bath.
After immersing the S-3KD61 round bar test piece for 8 hours.

It was taken out and air cooled.

After the treatment, the sample was cut and examined using X-ray diffraction and an X-ray microanalyzer, and as a result, it was confirmed that a chromium-iron carbonitride layer was formed on the two surfaces as in the other examples.

Example 6 NaCNO73wt%, NaNO28wt% and KN
A heat-resistant steel container containing a mixture of O38wL% and Na2Co31lwt% is heated in an electric furnace in the atmosphere,
A molten salt bath of 530'C is formed, and 110
15 wt % of pure chromium powder of 0 mesosh was added. This molten salt bath has a diameter of 81). JIS with a length of 15tm
-S-9A- After immersing a KD61 round bar test piece for 6 hours, it was taken out and cooled in the air.

After the treatment, it was cut and examined using XvA diffraction and an X-ray microanalyzer, and as a result, it was confirmed that a chromium-iron carbonitride layer was formed on one surface, as in the other Examples.

Example 7 NaCN 4.4 wt% and K1)0 wt% and Naz
A heat-resistant steel container containing the mixture with B4072Qwt% was heated in an electric furnace in the atmosphere to form a 650°C molten salt bath, and 15wt% of pure chromium powder of 1100 mesh was added to this bath. . A JIS-3KD61 round bar test piece with a diameter of 3+n and a length of 151)1 was immersed in this molten salt bath for 4 hours, and then taken out and cooled in the air.

After the treatment, the sample was cut and examined by X-ray diffraction and an xvA microanalyzer. As a result, it was confirmed that a chromium-iron carbonitride layer was formed on the two surfaces as in the other examples.

Example 8 - 64 = Same NaCN053 as used in Example 1 vy t%
A graphite container containing a mixture of 12 wt% KCl and 35 wt% CaCIz was heated in an electric furnace in the atmosphere and maintained at 570°C.
** Insert a pure chrome plate measuring 4 x m and use this as the anode.

Using the graphite container as a cathode, electricity was applied at an anode current density of 0.8 A/cJ for about 15 hours. Calculated from the weight reduction of the chromium plate due to this chromium anodic melting treatment.

Approximately 7% of chromium was dissolved in the bath based on the total salt bath volume. In this molten salt bath, a diameter of 61). 5KH5 of length 15 dragons
1 After soaking the round bar test piece for 24 hours.

It was taken out and air cooled.

When the treated specimen was cut and examined using an X-ray microanalyzer, it was found that carbon was present in the surface layer, as shown in Figure 6.
In addition to r, Fe and N, C was also observed.

Furthermore, the X-ray diffraction results showed good agreement with the diffraction of CrN, Cr2N, Fe, and C, so it was confirmed that the second surface layer was a chromium-iron carbonitride layer.

Similar to Examples 1 and 2, good adhesion results were obtained.

Example 9 NaCNO51wt%, NaCl21wt% and N
A graphite container containing a mixture of 82CO3 and 28wt% was heated to 570°C in an electric furnace in the atmosphere to prepare a molten salt bath.

Further, a J I 5-3KH51 specimen with a diameter of 6 mm and a length of 15 mm was immersed in this bath at 570°C to which 1200 mesos of Fe-Cr alloy powder was added at a rate of 10% based on the molten salt. was used as a cathode and the graphite container was used as an anode, and electricity was applied for 4 hours at a cathode current density of 0.05 A/cJA to perform electrolytic treatment. After treatment, the specimens were removed from the bath and cooled in air.

After cutting, the cross section of the surface layer was analyzed using an X-ray microanalyzer. As a result 2, as shown in FIG. 7, the 2nd surface layer contains Cr + Fe + N, C
was recognized.

Example 1O NaCN48 wt% and KCl12wt% and -100
After heating 2wt% of pure chromium powder from Mesos to 65oC and thoroughly stirring the molten bath to make it homogeneous.

To 4 parts by weight of this bath, 1 part by weight each of graphite and alumina powder was added and further mixed on top to prepare a processing agent for slurry coating.

After that, the processing agent is cooled and turned into powder.

Add alcohol to make a slurry, and make this into JIS-3KH51 with a length of 15 + n x width of 50 x 1 o x thickness.
Apply it to the top of the flat plate to a thickness of about 5ml.

Dry. The specimen was heated in a nitrogen atmosphere at 570'C for 8 hours and then cooled.

After removing the treatment agent adhering to the specimen, examination using X-ray diffraction and an X-ray microanalyzer revealed that there was a mixed layer mainly composed of Cr N + Cr 2 N + Fe * C on one surface, similar to other examples. It was confirmed that a chromium-iron carbonitride layer was formed.

Example 1) Same as used in Example 1, NaCN053 w
A heat-resistant container containing a mixture of 12 wt% KCl and 35 wt% CaCl was heated in an electric furnace in the atmosphere to form a molten salt bath at 570°C, and 1100 mesosh of pure chromium powder was added to the above mixture. It was added in an amount of 15 wt% based on the molten salt. In this molten salt bath, a J of 6.5 mm in diameter and 40 U+ in length was pre-baked under standard conditions.
After immersing the Is-3KH51 specimen for 8 hours, it was taken out and cooled in the air.

After washing off the adhering bath agent, the formed surface layer was examined by X-ray diffraction, and diffraction lines corresponding to CrN, CrJ, Fe, and C were observed.

Next, the chromium carbonitride-coated specimen (sample floor 1) was dry-tested using a Fabilly tester using gas carburized and quenched JIS-3CM415 as a mating material.

Load 400kg, rotation speed 30Orpm, friction speed 0゜1
A friction test was conducted under the conditions of m/see and test time of 4 m1n. In addition, for comparison, JIS-3KH51 quenching and tempering, a specimen (sample No., Sl), and nitriding treatment were performed. 5K
A similar friction test was also conducted on the H51 specimen (sample 1) &], s2).

The specimen of sample ms1 showed a wear amount of about 17 mg/cIIt, and the friction coefficient measured 30 seconds after the start of the test was 0.
．． It was 280. In addition, the test piece of Miyo S2 is approximately 15cm/
The friction coefficient was 0.265 30 seconds after the start of the test.

On the other hand, in the sample No. 1 according to this example, the amount of wear was as small as about 2.5 cm/cnl, and the coefficient of friction 30 seconds after the start of the test was as small as 0.093.

In addition, JIS 5KH51 specimens were coated with a vanadium carbide layer (VC) approximately 3 μm thick by immersing them in a high-temperature molten salt bath at 1020°C for 1.5 hours, or by chemical vapor deposition at 850°C for 24 hours. A similar friction test was also conducted on a JIS-3KHH51 specimen coated with a titanium carbonitride made of Ti (C,N) with a thickness of 8 μm by CVD.

The amount of wear and coefficient of friction were almost the same as those of sample No. 1 treated according to this example. From this, it can be seen that the surface layer formed by the two examples is not inferior in terms of wear resistance and seizure resistance compared to the surface layer formed by molten salt immersion method or CVD at high temperature.

[Brief explanation of the drawing]

Figures 1 and 4 are micrographs (400x) showing the cross-sectional structure of the surface layer formed by the treatment of the present invention in Example 1.2, Figures 2, 5, 6, and 4, respectively. Figure 7 is a diagram 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, 8, and 9, respectively, and Figure 3 is a diagram showing the surface formed in Example 1. FIG. 3 is a diagram showing the change in layer thickness of a layer with respect to immersion time.

Claims (6)

[Claims] (1) By coexisting an iron or iron alloy material, a chromium-containing material, and a treatment agent consisting of one or more of cyanide salts and cyanates of alkali metals or alkaline earth metals, A surface layer made of chromium carbonitride is formed on the surface of the iron or iron alloy material by heat treatment at 650° C. or lower to diffuse chromium, nitrogen and carbon onto the surface of the iron or iron alloy material. Surface treatment method for iron or iron alloy materials. (2) Iron or iron alloy material, material containing chromium, cyanide salt of alkali metal or alkaline earth metal, one or more types of cyanates, and chloride of alkali metal or alkaline earth metal substances, fluorides, boron fluorides,
Chromium, nitrogen, and carbon are removed from the iron by heat treatment at 650°C or lower in the presence of a treatment agent consisting of one or more of oxides, bromides, iodides, carbonates, nitrates, and borates. Alternatively, a method for surface treatment of an iron or iron alloy material, which comprises forming a surface layer of chromium carbonitride on the surface of the iron or iron alloy material by diffusing it onto the surface of the iron or iron alloy material. (3) The chromium-containing material is an iron or iron alloy material according to claims (1) and (2) comprising one or more of pure chromium, a chromium alloy, and a chromium compound. Surface treatment method. (4) The heat treatment is carried out by immersing the chromium-containing material and the iron or iron alloy material in a molten salt bath in which the treatment agent is melted. ) Surface treatment method for iron or iron alloy materials. (5) The heat treatment is performed by melting the treatment agent and electrolytically treating the iron or iron alloy material as a cathode in a molten salt bath in which the chromium-containing material is immersed. and a method for surface treatment of iron or iron alloy material according to item (2). (6) The heat treatment is performed in a state where a paste of mixed powder of the treatment agent and a material containing chromium is applied to the iron or iron alloy material.
2) The surface treatment method for iron or iron alloy material described in section 2).