JPS5830944B2 - Ionic sulfurization carbonitriding treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing iron-based members suitable for application to parts that come into sliding contact with each other.

As a means of imparting wear resistance and self-lubricating properties to the surface of an iron-based member to be treated, there is a method of simultaneously applying nitriding and sulfurizing.

A typical example of this is the Suru-Sulf method (Sur-8
u, gf method), which has been applied in many fields.

In this method, the object to be treated is immersed in a high-temperature salt bath containing CNO, CO3-, etc. as its main components.

However, since the salt bath adheres to the surface of the object to be treated, CN is generated during the treatment of washing wastewater or during treatment.
The disadvantage was that it was extremely difficult to remove from the salt bath.

Since the above-mentioned CN is a pollutant, the inability to remove it leaves problems in the disposal of wastewater.

In addition to the above-mentioned points, the surface layer in this treatment is composed of a nitrided layer with large crystal grains and a sulfurized layer, but its structure can be significantly changed depending on the ingredients of the salt bath. However, it is difficult to set the conditions, and it is also difficult to control the concentrations of N and S in the treatment layer.

Furthermore, since hardening is mainly caused by nitrides, materials with a small amount of nitride-forming elements have the disadvantage of being difficult to use under high loads.

On the other hand, recently, ion engineering treatment methods have been attracting attention as a solution to the drawbacks of surface treatment methods using salt baths.

However, only the ion nitriding method has achieved technical success, and only some successes have been reported for the ion carbonitriding method.

Furthermore, there are no successful examples of ion sulfurization, and hardly any examples of ion sulfurization or carbonitriding.

An object of the present invention is to provide a method for ionically sulfurizing and carbonitriding an iron-based workpiece having a sulfurizing and carbonitriding layer with excellent adhesion.

The present invention uses an ion surface treatment method in which the inside of the processing furnace is evacuated to 10 Torr or less, a processing gas is introduced, and a DC voltage is applied between the processing object as a cathode and an anode.
Glow discharge is performed in a dilute gas containing a carbon source, a nitrogen source, and a sulfur source.

A mixed gas of at least one of Ar, He, and H2 as a processing gas, N2 as a nitrogen source, a methane hydrocarbon gas as a carbon source, and H2S as a sulfur source, or a mixture of NH3, methane hydrocarbon, and H2S. It consists of a mixed gas.

As a result, a carbonitrided layer having wear resistance and self-lubricating properties and a sulfurized carbonitrided layer are formed on the surface of the workpiece.

If the amount of H2S is less than 0.01 volume φ, there is no sulfurizing effect;
The seizure resistance is comparable to that of conventional carbonitriding.

1, -1 Volume φ is converted to room temperature-atmospheric pressure, and is simply expressed as excellent below.

The amount of methane hydrocarbon gas should not be less than 0.01 atoms.

At 0.01 atoms or less, the wear resistance of the sulfur-carbonitrided layer matches that of the sulfur-nitrided layer within a variation range, and the effect is excellent.

Although CH4 is preferable as the methane-based hydrocarbon gas, it is also possible to use other higher-order methane-based hydrocarbon gases such as C2H6 and C3H8.

In this case, the amount of C in the methane-based hydrocarbon gas needs to be determined based on the amount of effective C.

The effective amount of C is calculated from the following equation, assuming that in addition to methane-based hydrocarbon gas, N2, NH3H2S, and all other gases are dissociated.

C atom%''''(.

+N+H+S+-t. (other cuffs) below, the atomic width is at%
and distinguish it from the volume φ.

If the above gas composition and processing temperature conditions are met,
In most cases a compound layer with a thickness of 3 to 50 microns is obtained.

This thickness is neither too thick nor too thin in order to provide wear resistance and self-lubricating properties to the surface of the workpiece.

Furthermore, it is desirable that the degree of vacuum be evacuated to Q, I Torr or less before introducing the gas.

Further, it is desirable that the degree of vacuum after gas introduction be maintained at 1 to 5 Torr.

Hereinafter, the process by which the present invention was made will be explained in order.

First, regarding the conventional ion carbonitriding method, since the ion carbonitriding method uses plasma during glow discharge as a means of activating nitrogen and carbon, non-polluting N2 or NH3, Cn
H2n+2 can also be used.

Moreover, not only the processing time is shortened, but also the amount of gas used can be significantly reduced because the processing is carried out in an atmosphere under reduced pressure.

The sputtering action continues during processing, and this removes scale from the surface of the object to be treated, so pre-treatment is useful even for objects made of metal materials that tend to form oxide layers on their surfaces. Ionic carbonitriding can be performed without the need for carbonitriding.

However, like the layer produced by conventional gas carbonitriding, this surface is hard, has low deformability, and does not have any self-lubricating properties.

Therefore, when this is used as a sliding fluffy part, initial fitting is poor and seizure and galling are unavoidable.

Next, we examined ion flux.

At present, the possibility of ion engineering surface treatment has been touched upon in part, but it has not been put to practical use.

Therefore, H2S is used as the S source, H2 is used as the diluent gas, and Ar is used as the diluent gas.
Mixed gas with at least one of pHe at 10'T
The sample was introduced into a vacuum chamber evacuated to a pressure below orr, and a glow discharge was generated to perform ion sulfurization.

As a result of experiments, it was found that in ion sulfurization, the morphology of the surface layer changes depending on the amount of H2S, and when the amount of H2S is 5% or more, the surface layer peels off after treatment.

As a result of X-ray diffraction, no S or S compound was found on the surface of the treated object after peeling.

In addition, there was no significant difference from the untreated material in the wear test, indicating that sulfurization had no effect.

On the other hand, when the amount of H2S was lower than 5, it was clear from the 400x cross-sectional photograph of the processed object shown in FIG. 1 that almost no S and S compounds were formed.

Although the presence of a trace amount of S compound was confirmed by X-ray diffraction, only a weak layer with weak adhesion was formed.

In addition, there was no significant difference from the untreated material in the wear test.

From the above, conventional ion carbonitriding is insufficient to be applied to sliding wear parts, and it is difficult to form a sulfurized layer with adhesiveness using ion sulfurization alone.

In order to provide a high degree of wear resistance and self-lubricating property, the inventors found that by forming a dense hexagonal sulfurized carbonitrided layer that is easy to plastically flow in the carbonitrided layer, and further provided with micropores. I found out.

The treatment method of the present invention described above can produce the above-described state with reproducibility.

Compared to the conventional treatment using a salt bath containing CN, the state of the sulfurized carbonitrided layer of steel is such that the compound is not iron nitride but iron carbonitride.

Therefore, the present invention is not only a non-polluting process that does not require CN, but also, considering that the compound layer is made of tough iron carbonitride, its effect is significantly greater than that of the 5ul-8ulf method. There is a difference.

Furthermore, compared to the conventional carbonitriding method, the method of the present invention has a significant effect on wear resistance because the compound has self-lubricating properties.

The type of gas and its composition are very important conditions in order to create a layer with good wear resistance and self-lubricating properties on the surface of the workpiece by ion sulfurization and carbonitriding.

Contains N2, methane hydrocarbon gas, and H2S, and the rest is A.
A material consisting of at least one of r, He, and N2 is used.

The composition of N2 is preferably 10 to 90%, especially 20 to 80%.
It is desirable to roll.

N2 causes S to coagulate and precipitate into a solid state, which promotes the subsequent diffusion of S into the interior.In order to prevent the agglomerated precipitates from peeling off during cooling after processing, a temperature of 10 or more is required. Limited.

As the amount of N2 increases, the diffusion of S, C, and N into the interior progresses.

The amount of diffusion into the interior of the object to be processed becomes maximum when N2 is 70%.

When the amount of N2 exceeds 90 yen, the progress of diffusion tends to decrease and the processing time to obtain the same thickness tends to be long, which is not desirable.

NH3 can be used instead of N2.

The amount of NH3 is limited to 10 to 90 when converted to the amount of N2.

Figure 2 shows the results when a chromium-molybdenum steel material SCM21 was treated at 550°C for 2 hours in a gas consisting of N2, 0.3 tons of H2S, 1 at% methane-based hydrocarbon gas, and N2. Compound layer thickness and N on the surface of the treated object
The relationship between the two compositions is shown.

The influence of N2 composition is clear from this figure.

Among the remaining gases other than N2, H2S has the role of forming an S compound on the surface of the object to be treated.

If the amount of N2S exceeds 5 ml, the S compound will easily peel off or fall off during cooling after processing, so the amount of H2S should be set at 5 ml.
limited to iniquity.

On the other hand, if the amount of N2S is too small, the sulfurizing effect tends to decrease, so it is preferably 0.01% or more.

Next, N2. Among the remaining gases excluding N2S, methane-based hydrocarbon gas has the role of supplying C into the object to be treated and forming fine iron carbonitrides.

If the amount of methane-based hydrocarbon gas exceeds 10 atφ, the nitriding effect will be inhibited and the effect on wear resistance will be weakened.
It is preferably 0 atφ or less.

On the other hand, if the amount of methane-based hydrocarbon gas is too small, carburization, refinement, and hardening will not be sufficient, so 0.01atφ
The above is preferable.

Figure 3 shows the treatment of 550% of chromium molybdenum steel SCM21 as a workpiece using a mixed gas consisting of 50% N2, 1at% methane hydrocarbon gas, N2 and N2S.
The results of the Okoshi type abrasion test are shown for the samples treated at ℃ for 2 hours.

The conditions for the wear test were a load of 2.6 kg and a wear rate of 2.9.
1m/S, wear distance 200m, lubricating oil is turbine oil #1
It is 20.

In FIG. 3, the vertical axis shows the wear loss, and the horizontal axis shows the composition of N2S.

In order to make the S compound contribute to self-lubrication and reduce wear loss, the above-mentioned range is preferable, and 0.1 to 2 is particularly preferable.

Figure 4 shows a mixture of 50 tons of N2, 0.5 tons of H2S, N2, and methane-based hydrocarbon gas, chromium-molybdenum steel SCM21 as the object to be treated, and 550°C.
, shows the results of an Okoshi type abrasion test performed on a sample that has undergone a 2-hour treatment.

The conditions for the wear test were the same as for the results shown in FIG.

In FIG. 4, the vertical axis shows the wear loss, and the horizontal axis shows the effective amount of C in the methane-based hydrocarbon gas.

In order to make iron carbonitride contribute to wear resistance and reduce wear loss, the above range is preferable, especially 0.1 to 7.
It is clear that at% is preferred.

At least one of Arn He, N2 as a diluent gas,
It performs functions such as cleaning the surface by sputtering and controlling temperature.

Since these gases are non-polluting, there is no difficulty in processing the exhaust gases.

Although H2S is harmful, it does not cause any particular problems because it is mostly diluted in the vacuum chamber.

Among Ars He and N2 as the diluent gas, N2 is most preferred, and the amount of the diluent gas is particularly preferably 20 to 80%.

Figure 5 shows the results when a chromium molybdenum steel material SCM21 was treated at 550°C for 2 hours in a gas consisting of NH3, 0.3% H2S, 1 at% methane hydrocarbon gas, and N2. It shows the relationship between the thickness of the compound layer on the surface of the object to be treated and the NH3 composition.

The influence of NH3 composition is clear from this figure.

The object to be treated is preferably a general metal material.

In particular, in steel materials, N compounds, C compounds, S compounds, and even composite compounds of C and N are easily formed, and these compounds work effectively for wear resistance.

The processing method of the present invention is carried out as follows.

A mixed gas of N2 or NH3, methane-based hydrocarbon gas, H2S, and diluent gas is introduced into a vacuum chamber which is evacuated to 10 Torr or less.

The depressurized chamber is equipped with an object to be treated that serves as a cathode and an anode.

A furnace body may also be used as an anode.

A voltage is applied between the anode and the cathode to form a glow discharge.

The mixed gas in the decompression chamber is ionized by glow discharge, and some N, C, and S are generated by dissociation and collide with the object to be processed.

The collided N, C, S, etc. react on the surface of the object to be treated, forming two treatment layers: a sulfurized carbonitrided layer and a carbonitrided layer in which sulfides are dispersed.N and C form a compound. With,
It diffuses into the object to be treated and increases the hardness of the lower part of the surface compound layer.

Due to the continuation of the glow discharge, the above-mentioned reaction and diffusion infiltration are carried out continuously during the treatment, and an effective amount of the treatment layer is formed.

-1 The processing power level is kept constant during processing by adjusting the input power supply.

In the method of the present invention, in order to effectively form both a sulfurized carbonitrided layer and a carbonitrided layer in which sulfides are dispersed in the carbonitrided layer, the temperature range is limited to 400 to 600°C.

If the temperature is below 400°C, the diffusion of N and C will be slow, and if it is above 600°C, there is a risk of thermal deformation.

The present invention has an extremely large effect of being non-polluting compared to the sulphonitriding method using a salt bath, but it is also superior to ion carbonitriding and ion sulfurizing in the following points.

In ion carbonitriding, only an iron carbonitride layer and a hardened layer due to diffusion and penetration of N and C are obtained, and the treated layer has no self-lubricating property.

According to the present invention, a treated layer in which S compounds are uniformly dispersed in iron carbonitride is obtained, and this layer has higher deformability and self-lubricating properties than a layer containing only iron carbonitride. becomes.

Therefore, compared to ion carbonitriding, initial conformability is improved and seizure, galling, etc. can be prevented.

In addition, the compound layer formed on the outermost surface by ion carbonitriding is a layer with low deformation resistance and is not sufficient in terms of wear resistance, but in the present invention, the compound layer formed by carbonitriding and the S compound are mixed. This makes effective use of the compound layer for wear resistance.

On the other hand, the present invention can diffuse nitrogen and carbon to form a carbonitrided layer, even in the case of mild steel materials, where conventional sulfonitriding has insufficient hardness just below the surface layer and has problems in terms of wear resistance. According to
One of its characteristics is that it can be hardened.

Therefore, even for materials that do not contain nitride-forming elements, it is possible to significantly improve the problems of initial conformation, seizure, and galling.

Also, in the present invention, N diffuses into the interior of the hardened layer as in ion carbonitriding, and the depth of the hardened layer is the same as in conventional ion carbonitriding.

On the other hand, as revealed by the inventor's studies, the ion sulfurization method cannot form an effective compound layer on the surface of the object to be treated.

According to the present invention, since the formation of the S compound changes from the Fe-S system to the Fe-8-NC system, a more stable S compound can be obtained.

First, in ion sulfurization, the S compound is only deposited on the surface of the object to be treated, and since the bond between the compound and the object is weak, the S compound is removed during the treatment due to the sputtering effect caused by glow discharge. There was a strong possibility that it would be thrown off the surface.

In the present invention, since the S compound is formed by a Fe-8N-C system reaction, the S compound is stably dispersed and precipitated in the compound layer on the surface, and there is less possibility of it being repelled by the sputtering action. Ru.

As a result, the present invention can easily form S compounds, which are difficult to form using ionic sulfurization.

Furthermore, the S compound thus formed has self-lubricating properties, which greatly helps to improve problems such as initial break-in, seizure, and galling against wear.

The present invention will be explained in detail below.

Example 1 The treatment method of the present invention was carried out using a cold rolled steel plate SPC as the object to be treated.

First, the object to be treated was used as a cathode, the vacuum furnace body was used as an anode, and H2 gas was introduced into the vacuum furnace body which was previously evacuated to 10'' Torr or less.

After adjusting the exhaust volume and the amount of introduced gas to make the pressure in the vacuum furnace 3T□, a high voltage was applied between the two electrodes to form a glow discharge.

While continuing glow discharge, the temperature of the object to be treated is increased,
Furthermore, during that time, the surface of the object to be treated was cleaned by sputtering.

After the temperature of the object to be treated reaches 550°C and the surface has been sufficiently cleaned, the introduced gas is changed from H2 to N2. CH,, H2S, H
I switched to a mixed gas consisting of 2.

The degree of vacuum was maintained at 3 Torr.

Among them, the mixed gas composition is N2/H2=1/1. CH, is 1
at%, H2S is 0.5%.

After introducing the mixed gas, the temperature was maintained at 550° C. and treatment was performed for 2 hours.

FIG. 6 shows a cross-sectional structure of the object to be processed obtained by processing under the above conditions, enlarged 400 times.

In contrast, in the example shown in Figure 1 where SCM21 was subjected to ion sulfurization, no compound layer was formed at all, whereas the treated layer according to the present invention had a thickness of about 15 μm, as is clear from Figure 6 (400x magnification). Ion sulfurized carbonitrided layer of 1 button and about 10μ
A carbonitrided layer 2 was formed, and acicular nitrides were further formed below it.

The X-ray diffraction results of the above treated object are shown in FIG. 7, and it was confirmed that an S compound was present in the surface compound layer.

First, the surface compound layer shown in FIG. 6 was formed in which the S compound was uniformly dispersed.

Furthermore, the measurement results of the hardness distribution of the cross-sectional structure shown in FIG. 6 are as shown in FIG.

In FIG. 8, the vertical axis shows the Vickers hardness and the horizontal axis shows the distance from the surface, and the measurement was carried out using a 100 g micro Vickers hardness meter.

As is clear from the figure, the surface compound layer has a Hv of 600 to 7.
It had hardened to 00.

Example 2 The treatment was carried out under the same conditions as in Example 1, using chromium molybdenum steel SCM21 as the object to be treated.

The cross-sectional structure and surface X-ray diffraction results after treatment were similar to those of SPC in Example 1, and the obtained surface compound layer also had the S compound uniformly dispersed therein.

The above treated material according to the present invention and N2/H2=1/1.1a
FIG. 9 shows a comparison of wear tests of SCM21 subjected to ion carbonitriding in t% CH gas at 550° C. for 2 hours.

The figure shows the results of the ultra-thin type wear test.

The test conditions were: mating material 5UJ-2 (Rc 60 or more), wear distance 200m, lubricating oil was turbine oil #120, and the load was 12.6! It has 9 buttons and weighs 18.9 kg.

In the figure, A1 and A3 and A4 of the present invention are ion carbonitriding.

Also, A1 and 3 have a load of 18.9kg, and A1 and 4 have a load of 12.6kg.
It is g.

As is clear from the figure, the treatment according to the present invention has a higher
Its wear resistance was significantly improved.

y>, in Examples 1 and 2, N2CH4 gas, H2S, and H2 were used as the mixed gas, but even if Ars He or two or more gases of Ar, He, and H2 were used as the diluent gas in addition to H2, The same processing as in the above example was possible.

Moreover, the obtained treated layer also had the same wear resistance as Example 2.

Furthermore, C2H6, C3H8 as methane hydrocarbon gas
Similar treatment was possible when using high-order materials such as, and the wear resistance was also excellent.

Example 3 Using the same material to be treated as in Example, CH,
The treatment was carried out at 550° C. for 2 hours using a mixed gas consisting of 1 at%, H2S 0.5% and the remainder NH3 decomposed gas.

As a result of observing the cross-sectional structure of the treated material, approximately 1
A compound layer of a 5 μm thick sulfurized carbonitrided layer and a carbonitrided layer were formed thereunder.

Further, as a result of measuring the hardness, the hardness of the surface compound layer was 600 to 700 in Witzkers hardness.

As described above, according to the present invention, a sulfurized carbonitrided layer can be formed on the surface of the object to be treated using an ion-engineering treatment method.

In addition, the treated layer becomes the same level as when using a conventional salt bath, or has a fine layer.

Therefore, it is suitable as a replacement for the above-mentioned conventional method which is polluting.

[Brief explanation of drawings]

Figure 1 is a cross-sectional micrograph of a product subjected to ion sulfurization by the conventional method, Figure 2 is a diagram showing the relationship between the thickness of the sulfurized carbonitrided layer and the amount of N2 subjected to the treatment method of the present invention, and Figure 3 is A diagram showing the relationship between the amount of H2S applied to the treatment method of the present invention and the abrasion loss. Fig. 4 is a diagram showing the relationship between the amount of C applied to the treatment method of the present invention and the abrasion loss. NH applied to treatment method
6 is a cross-sectional micrograph showing an example of the treated material of the present invention, and FIG. 7 is a diagram showing the relationship between the amount of 3 and the surface compound layer. FIG. A graph showing the X-ray diffraction results, Figure 8 is a diagram showing the hardness distribution of the treated layer of the treated material of the present invention, and Figure 9 is a diagram showing the relationship between wear loss and wear rate by ultra-thin wear test. be. 1... Ion sulfurized carbonitrided layer, 2... Carbonitrided layer.

Claims (1)

[Claims] 1. In the ionic surface treatment method, a gas is introduced and a direct current voltage is applied between the iron-based workpiece as a cathode and an anode in a reduced pressure atmosphere to generate glow discharge. In terms of nitrogen: 10-90 volumetric, hydrogen sulfide: 0
．． 01 to 5 volume φ, methane hydrocarbon 0.01 to 10 atoms φ, and the balance is hydrogen, at least one of argon and helium, and in this gas, 400 to 60
An ion sulfurization carburization window treatment method, characterized in that the treatment is carried out at 0° C. to form a carbonitrided layer on the surface of the object to be treated and a sulfurized carbonitrided layer on the surface of the carbonitrided layer.