JPS58197264A - Surface treatment of industrial material - Google Patents

Abstract

PURPOSE:To deposit carbides of Cr or the like easily and firmly on an industrial material contg. a specified amount of carbon, by melting the fluoride or the like of a I a or IIa group element in the periodic table or Al by heating, putting an element such as Cr in the molten bath, and immersing the industrial material in the bath while carrying out electrolysis for aging using the element as an anode. CONSTITUTION:>=1 Kind of compound selected from the fluorides, borides and chlorides of the I a and IIa group elements in the periodic table and Al is melted by heating, and >=1 kind of element selected from Cr, Ta, Nb, V and Zr or an alloy thereof is put in the molten bath. An industrial material contg. >=0.05% carbon is immersed in the bath for a fixed time while or after carrying out electrolysis for aging by using the element or alloy as an anode. Thus, a layer of the carbide of at least one of Cr, Ta, Nb, V and Zr can be deposited on the surface of the industrial material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of industrial materials, in particular,
Or, Ta, Nb, V.

Adding one or more of Zr elements and performing aging electrolysis using this as an anode, or after that, by immersing an industrial material containing carbon in this bath, the above-mentioned Cr, Ta, Nb,
Carbides of the elements V and Zr are deposited and layered on the entire surface of the industrial material.

Generally, materials with high melting point, high hardness, high oxidation resistance, and high corrosion resistance are used, such as Cr, Ta, Nb, and V.

Zr carbide has been attracting attention, and many uses have been proposed. However, due to its high hardness, it lacks toughness, and it is still impossible to sinter itself and use it as a mechanical part. For this reason, there have been methods for uniformly and firmly coating the surfaces of industrial materials, and an increasing number of methods have been proposed in recent years.

Conventional methods can be broadly divided into chemical methods and physical methods. Physical methods have the advantage of being relatively new and can be processed at low temperatures, but require complex equipment and are limited in shape.

On the other hand, chemical methods have been practiced for a relatively long time and include gas methods, powder methods, and salt bath methods.

The gas method has the advantage of being able to coat compounds containing a wide range of elements and their carbides, but there is a possibility of generating toxic gases such as hydrogen chloride, and the use of dangerous gases such as hydrogen is disadvantageous. Due to the necessity, the device requires a dog. Further, the powder method is generally considered to have poor properties such as coating adhesion. Salt bath method (2) Various methods have been proposed, but the one that has been put into practical use involves mixing coating elements in a salt bath whose main component is boric acid or borate, and immersing the steel material in it. It's a method.

This method uses a simple device and can be treated relatively easily, but since boric acid or borate is the main component, the viscosity of the salt bath is very high, and therefore a large amount of salt adheres to the treated product.

In addition, there are problems such as the high temperature corrosion resistance of the container and the difficulty in removing salt adhering to treated products, so it is desired to develop a salt bath with better operability.

This invention solves the above-mentioned problems, and its purpose is to improve Crr and Ta for industrial materials.

To easily and firmly adhere carbides of the elements Nb, V, and Zr, and to obtain a surface treatment state of an industrial material with excellent characteristics.

That is, this invention relates to the fluorides, bromides and chlorides of elements belonging to Ia and IIai of the periodic table, the fluorides and bromides and chlorides of Al, one or two of these, as shown in Example 2. In a heated melt bath of a mixture of two species, Or, Ta, Nb, V.

One or more of the elements Zr or an alloy thereof is added, and while performing ripening electrolysis using this as an anode, or thereafter, an industrial material containing at least 0.05% of carbon is added to the bath. By soaking for an hour, the or
The present invention relates to a surface treatment method in which at least one carbide of Ta, Nb, V, and Zr is deposited and layered on the surface of the industrial material.

The bath used in this invention is not special;
Especially Kcl, N used for normal quenching heating of steel.
Typical examples include chlorides of elements belonging to 1a or ■a of the periodic table such as acl and Baclz, fluorides of elements such as NaF, or those containing only these fluorides as the main component. . In addition to the chloride, a bath containing the chloride of A1 as the main component may be used.

The gist of this invention is to use a special di-salt bath as a bath composition, which has not been previously possible, and to use Or.

Ta, Nb, V, Zr elements or alloys thereof are used as an anode,
Only by adding the step of ripening electrolysis (-therefore, continuous coating treatment is possible after that. Once the bath is prepared, the missing elements can be added as they are or in the form of an alloy. The work can be continued without any interruptions and is efficient.

In addition, general (in the case of a dichloride bath, for prevention of oxidation (-
Although treatment in a neutral atmosphere such as argon is required, the treatment of the present invention allows treatment in the atmosphere. Note that, of course, processing in a neutral atmosphere is also possible.

This treatment salt bath has various characteristics such as availability and price, chloride removal, -'(N'acl, Kcl
, Baa 12 often uses NaF as the fluoride.

When using, two or more chlorides are mixed to adjust the melting point, and an appropriate amount of difluoride is usually added. Depends on the deposition rate of salt and the difficulty of removing the deposited salt.In other words, if the amount is too low, the deposition rate will decrease, and if it is too large, it will be difficult to remove the deposited salt.Therefore, the practical lower limit is 0.3% (mol). ) The upper limit is about 70% (mol).Furthermore, the coating metal to be added is often a ferroalloy in practice, and the amount added is less than 0.5% (mol) in relation to the coating speed. This should be considered as the lower limit.Additionally, too much addition may increase the viscosity of the bath and cause problems such as entrainment and adhesion to the surface of the treated product, so the corresponding element should be around 60 parts (mol). The processing temperature should be determined by the rate of coating formation and the base material, but should normally range from 750C to 1100C.

As is well known, chloride has a low viscosity in the salt bath, and therefore the amount of salt adhering to the treated product is also small. In addition, salt is easily dissolved in water, and adhering salt can be easily removed. In the case of the salt of this invention, the amount of chloride is practically large, and the fluoride is removed at the same time as the chloride is dissolved, so it is very easy to remove the attached salt.

In the past, there have been reports that a carbide coating was obtained by adding vanadium to a molten salt whose main component was chloride and immersing steel in it, but it was also reported that carbide coating could not be obtained using Nb, which is a member of the same family. There is. Therefore, we estimate that this processing method is unstable. In fact, in preliminary experiments leading up to this invention, V.

A stable coating has not been obtained in a salt bath to which elements such as Nb and Ta have been added.

Electrolysis conditions vary depending on the bath temperature and salt bath amount, but the bath temperature is 75
0C~110oC1 Current density 0, IA/dm2~
500 A/dm'' and an electrolysis time of about 5 minutes to 5 hours are practical.

Carbide coatings are formed by the reaction between coating elements and carbon in industrial materials, but it can be applied by infiltrating carbon into iron with a small amount of carbon through a process such as carburizing, or by adding carbon to a salt bath. Similar results can be obtained by adding carbon and supplying carbon from outside the steel.

This invention is a salt bath treatment method that is easy to operate as described below, but as a result, the coating formation speed is faster than the boric acid or borate method, and the time required to form a coating of the same thickness is shortened. It was also found to be effective in reducing processing costs.

Examples of this invention are shown below. For reference, FIG. 1 shows the processing speed according to the present invention.

Example 1 Mixed powder 2o01 of 33% sodium chloride, 33% potassium chloride, 20% sodium fluoride, and 14% ferrovanadium (54% vanadium) was placed in a stainless steel container,
900 tl''' was melted by heating, and then electrolysis was carried out for 1 hour at a current of 20 A/dm'' using a plate-shaped ferrovanadium (54% vanadium) as an anode and a separately charged electrode as a cathode. After finishing, Sono Middle E JIS 5KD11 (
Shape Thickness 6m, Width 1. A test piece of Q rum, length 50m) was put in and held for 1 hour, then taken out, and after air cooling, diluted with water and diluted salt.
It was washed and removed, and X-ray diffraction was performed to confirm the coating layer and the layer. A photograph of the cross-sectional structure of the test piece is shown in Fig. 2. As can be seen from the photograph, the presence of a uniform coating layer of 10 μm in thickness can be confirmed on the surface of the iron 7-steel. Further, from the results of X-ray diffraction, it was confirmed that it was vanadium carbide (VC).The X-ray diffraction results are shown in FIG. After that, when the process is continued, the thickness of the coating layer suddenly decreases from a certain stage. Finally (after confirming that it becomes about 2 to 3μ in the same time, add the same amount of ferrovanadium powder (54%) as when preparing the bath, and then perform the pre-treatment. As a result, we were able to form a coating layer with the same thickness as in the first case.

44 moles of potassium chloride, 19 moles of barium chloride, 1% mixed powder of 37 moles of thorium 2002
was placed in a stainless steel container and heated to melt it to i''o o o C, and tantalum was put into it, and aging electrolysis was carried out for 30 minutes with a current of 30 A/dm2 using tantalum as an anode. 5KDII (shape: thickness 6, width I
A test piece of Qm (length: 50 m) was put therein and held for 2 hours, then taken out and cooled. From the structure of the test piece and the X-ray diffraction results, the presence of a 24μ TaC coating was confirmed. FIG. 4 shows the surface structure, and FIG. 5 shows the line diffraction results.

Example 3 A mixture of potassium chloride 601, sodium chloride 6051-1, sodium fluoride 601, and metallic chromium 301 was placed in a stainless steel container and heated and melted at 900 C. The metallic chromium precipitated in the bath was used as an anode, and a current was applied. 10 A/d
Carry out aging electrolysis for 2 hours at m”.After that, JISS
A test piece of K-3 (shape: thickness: 6 mm, width: 10 mm, length: 50 m) was placed and held for 5 hours. After the treatment was completed, the test piece was taken out and cooled in air. After cooling, it was washed with water to remove adhering salts, and then cut, and the structure was observed and the surface hardness was measured. Also, the coating layer was confirmed by performing X-ray diffraction. As a result, a coating layer of 13μ and a surface hardness of Hv2032, 21.88 were confirmed. At the same time, the presence of chromium carbide Or3C7 was also confirmed.

After that, we continued the experiment to confirm the lifespan, and found that approximately 1
After 00 hours, the coating layer became very thin, so 3
0g - A post-treatment after adding metallic chromium was carried out. the result,
Results comparable to those obtained in the initial stage of the experiment were obtained.

Example 4 To mixed powder 2001 containing 32% by weight of potassium chloride, 46% by weight of barium chloride, and 22% by weight of attenuated sodium, 9% by weight of zirconia was added and melted by heating at 1000C, and the added zirconia was used as an anode to conduct aging electrolysis. Current 20 A/dm
2 for 5 minutes, and JIS 5K in the bath while continuing electrolysis.
S-3 (shape thickness: 6 stone, width: 10 mm, length: 50 Tnrr
The test piece (l) was added and held for 1 hour. After that, it was pulled out and air cooled. After cooling, it was washed with water and the surface hardness and cross-sectional structure were observed. The surface was also identified using X-rays. As a result, a surface hardness of around 1500 Hv and a coating layer thickness of 32 μm were confirmed, and the presence of zirconia carbide was also confirmed.

In the life test, the same results as in Example 3 were obtained and there were no problems.

Example 5 A mixed powder of 34% by weight of potassium chloride, 48% by weight of barium chloride, and 18% by weight of sodium fluoride was placed in a stainless steel container (-) and 1000 tZ' was heated and melted in two parts.
2゛Eloniobium (64% nios 0.37 tantalum) 1
Add 6% by weight and use it as an anode to generate a current of 20 A/dm.
2, aging electrolysis was performed for 2 hours. After electrolysis, JIS 5
A test piece of KD-11 (same shape as Example 4) was immersed in the bath, held for 1 hour, and then cooled in air. The presence of a 27μ niobium carbide coating was confirmed by microscopy and X-ray diffraction.

Example 6 The salt bath of Example 1 was heated to 1000C, and a graphite test piece (shape: 5 holes in thickness, 10 m in width, 5 Qai in length) was immersed in the bath and maintained for 3 hours. After the treatment, the cross section of the specimen was observed under a microscope, and it was found that a coating layer of 15μ had been formed.
As a result of line diffraction, it was confirmed that it was vanadium carbide.

[Brief explanation of the drawing]

Figure 1 is a graph showing processing speed, Figure 2 is a cross-sectional micrograph of the structure, Figure 3 is an X-ray diffraction graph of the Cu target, Figure 4 is a micrograph of the cross-section of the CO target, and Figure 5 is a micrograph of the CO target. It is an X-ray diffraction graph. 11! ! t11-ノ ())

Claims (1)

[Claims] Periodic Table 1a, fluorides and bromides of elements belonging to [a] (dichloride, fluoride and bromide of Al, and chloride,
Or, Ta, Nb in a heated melting bath of one type or a mixture of two or more of these. One or more of the elements V, Zr, or an alloy thereof is added, and while performing aging electrolysis using this as an anode, or after that, an industrial material containing at least 0.05% of carbon is added to the bath. By soaking for an hour, the O
r, Ta, Nb, V. A surface treatment method comprising depositing and layering at least one carbide of Zr on the surface of the industrial material.