JPH0874025A - Member coated with chromium carbide by thermal spraying - Google Patents

Abstract

PURPOSE: To make an important contribution to an improvement in wear resistance and erosion resistance by forming a thermally sprayed film of chromium carbide by a reformed layer adhered and impregnated with Cr23 C6 type chromium on its surface layer. CONSTITUTION: A chromium carbide cermet film 2 which is formed by a thermal spraying method on a metallic base material 1 consisting of of iron, steel or super alloy is shown in (A) of Fig. In the Fig., (B) illustrates the film 2 of (A) after the film is brought into contact with chromium halide vapor contg. high-temp. gaseous hydrogen. The very small metal chromium 3 precipitated in the gaseous chromium halide atm. infiltrates the film 2 through the pore parts 4 of the film and metallurgically bonds thereto by reacting with the base material 1 and forming an allay metal 5. While the very small metal Cr adheres on the surface, the metal Cr reacts with the chromium carbide components or the free carbon included therein and forms the Cr23 C6 type chromium carbide 6. As a result, the reforming with the surface layer of the thermally sprayed film of the chromium carbide is executed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a chromium carbide sprayed coating portion.
Material, especially chromium carbide sprayed on the surface of base material
Coating or chromium carbide cermet spray coating
On the surface of Cr _{twenty three}C₆Type Chromium Carbide Coated or Inside
By invading Cr_{twenty three}C₆Type carbide impregnated
The present invention relates to a composite member formed by forming a modified layer.
It Such parts are subject to chemical and mechanical damage.
Easy boiler, steam turbine, gas turbine, blower
-, Pumps, crushers for coal and ore, conveyors, etc.
It is used in the field.

[0002]

2. Description of the Related Art In general, a thermal spray coating is formed by melting or softening a powder material such as metal, ceramics or cermet by a combustion flame of plasma or a combustible gas, and then removing these particles onto the surface of the base material (workpiece). It is obtained by spraying on and has the following features.

(1) When metal or alloy particles are sprayed in the atmosphere, the surfaces of the particles are covered with an oxide film, so that the particles are bonded to each other through the oxide film. Therefore, the interparticle binding force is weak, and since the particles are sprayed with pores, the denseness is poor and the adhesion to the object to be treated is poor. (2) Unlike metals, thermal spray materials of ceramics such as oxides, borides, carbides, and nitrides are difficult to completely melt in a thermal spray heat source, and are brittle materials. Becomes insufficient. Therefore, the particles are easily broken by the collision energy when the particles are sprayed.
Further, the carbide and nitride coatings are oxidized and decomposed in a high-temperature thermal spray heat source to deteriorate, and therefore have more pores and poorer adhesion than the metallic coatings. (3) In order to make up for such defects, conventionally, carbide, Co, Ni,
Cermet thermal spraying has been developed in which a metal such as Cr is added and the property of the thermal spray coating is improved by using this as a binder, and most of the carbides are practically used in this cermet thermal spray coating. However, even if a film is formed using a cermet thermal spraying material, it has not yet been possible to prevent the above-described generation of pores and reduction in adhesion.

Further, as a method for compensating for the drawbacks of the conventional thermal spray coating, especially for the above cermet thermal spray coating, JI
As in the case of S H0803 prescribed self-governing alloy sprayed coating, a method of heating the sprayed coating to near its melting point to bring the sprayed coating into a molten or semi-molten state and metallurgically bonding it to the substrate to be treated is available. is there. However, this method has a problem that the alloy components that can be used are limited and that this method cannot be applied to a carbide spray coating.

In addition, a method of spraying a Ni-Cr alloy on the surface of a substrate and then coating or invading Al and Cr on the surface of the sprayed coating and the pores thereof by a chemical vapor deposition method (Japanese Patent Laid-Open No. 55-104471). (See Japanese Patent Laid-Open Publication No. 6-52200), a method of subjecting a sprayed coating of an alloy obtained by adding at least one kind of rare earth element to a metal material containing at least one kind of Cr, Ni, Al and Co to Cr or Al diffusion permeation treatment (JP-A-56) -51567), and after spraying a heat-resistant alloy material consisting of Ni-Cr alloy,
A method of applying Al-Si powder or a slurry solution in which Al powder is suspended in an organic solvent and then heat-treating this to diffuse and permeate Al-Si powder or Al into the pores of the thermal spray coating (special For example, see JP-A-57-54282).

[0006]

As a method for modifying the thermal spray coating as described above, for example, for a metal thermal spray coating, a method of heating and melting, a method of diffusing and penetrating other metal components into the thermal spray coating, etc. Is being considered. However, even though these methods are effective for modifying the metal sprayed coating, they are often not applicable to the carbide-based sprayed coating. For modification of the carbide-based sprayed coating, the spraying method or The emphasis was placed on the development to reduce the pore generation rate by improving the thermal spraying conditions and to improve the adhesion.

However, such improvement efforts alone could not completely prevent the formation of pores in the thermal spray coating. In order to eliminate the residual porosity, a method such as coating the surface of the carbide-based sprayed coating with a paint or sealant in which an organic polymer material is dissolved in a solvent to close the porosity is taken as a countermeasure. However, it is not a modification of the carbide spray coating itself, so a complete solution has not been reached.

The main object of the present invention is to eliminate the defects of the conventional thermal spray coating of carbide formed on the surface of a member. Another object of the present invention is to eliminate the pores of the chromium carbide sprayed coating or the chromium carbide cermet sprayed coating (hereinafter, simply referred to as "chromium carbide sprayed coating") formed on the surface of the member, and activate the surface hard. It is to improve the adhesion of the thermal spray coating to the base material as well as to modify it with a chromium compound. Yet another object of the present invention is to provide Cr ₃ C ₂
By coating the surface of the chromium carbide-based sprayed coating containing Cr ₇ C ₃ as the main component with Cr ₂₃ C ₆ type chromium carbide, and by permeating the inside to modify the coating, the microhardness of the coating is improved. And improving the density. Still another object of the present invention is to improve the corrosion resistance, wear resistance and erosion resistance of the chromium carbide sprayed coating formed on the surface of the member.

[0009]

[Means for Solving the Problems] The present invention, which was developed as an effective means for achieving the above-mentioned object, has been proposed for the use of Cr ₃ C ₂ , Cr ₇ C ₃ chromium carbide or free carbon or a metal having a weaker carbon affinity than Cr. By thermally treating a chromium carbide sprayed coating containing Cr ₃ C ₂ and Cr ₇ C ₃ containing carbides as main components in an atmosphere containing chromium halides containing hydrogen, a chemical reaction is generated by the hydrogen reduction reaction during this heat treatment. active particles of fine metallic Cr by reaction of the the deposit on the thermally sprayed coating surface is permeated inside even through such pores simultaneously and the activated metallic chromium and the film component (free carbon, etc.), Cr ₂₃
The film is modified by forming C ₆ type carbide.

That is, according to this method, the fine particles of chemically active metal Cr deposited on the above-mentioned chromium carbide sprayed coating cover the sprayed coating and penetrate into the inside thereof, especially inside the pores, and By mainly reacting with the thermal spray coating or free carbon contained in the coating (including those supplied from metal carbides having a weaker carbon affinity than Cr) to form new Cr ₂₃ C ₆ type carbide, Improves micro hardness and density. The present invention developed based on such an idea has the following gist configuration.

(1) A base material and a chromium carbide sprayed coating formed on the surface of the base material. The chromium carbide sprayed coating is a modified layer in which at least the surface layer is adhered and impregnated with Cr ₂₃ C ₆ type chromium carbide. A chromium carbide spray-coated member characterized by being formed by layers.

(2) Carbides forming the above chromium carbide sprayed coating formed on the surface of the base material are Cr ₃ C ₂ or Cr ₃ C ₂ and Cr ₇ C
It is characterized by containing a mixture with ₃ .

(3) The above chromium carbide sprayed coating contains a coating
As a component, Cr without free carbon₃C ₂, Cr₇C₃carbide
Or if these contain at least 0.01-5 wt% free carbon
Or 0.1 for a metal carbide with a weaker carbon affinity than chromium.
~ 100 wt% contained. (4) The above-mentioned carbide sprayed coating is made of carbide or this carbide.
At least one selected from Ni, Cr and Co
Thermally sprayed carbide cermet prepared by mixing the above metals
To use. (5) Carbide or carbide cermet spray coating is
Heat energy or flammable gas explosion or combustion flame
It is formed by a thermal spray method as a source. (6) In an atmosphere containing chromium halide containing hydrogen gas
Heat treatment is performed using chromium chloride and chromium bromide as chromium halides.
At least chromium, chromium fluoride or chromium iodide
Also installed in a kind of gas or in powder that produces this gas
And hydrogen gas in an atmosphere heated to 500 to 1200 ° C.
Fine metal chromium chemically active by reduction reaction with
Is performed by a method of precipitating. (7) Above Cr_{twenty three}C₆Type chromium carbide modified layer
Mixture of hydrogen gas and halogenated gas in the reaction tank.
While adjusting the total molar ratio to be 1/4 to 4/1,
By heat treatment in a heating atmosphere of 500-1200 ℃
Chemically active fine metal chromium is deposited and sprayed
It adheres to and impregnates the surface of the film, and its diffusion penetration thickness is 1 to
Set to be in the range of 30 μm.

[0014]

The features of the present invention will be summarized as follows.
Active on the surface of the coating and its interior, especially inside the pores
The reaction between the converted metallic chromium and free carbon in the film
Generated Cr_{twenty three}C₆-Type carbide is coated on the surface of the film
Along with the penetration into the coating, the spray coating
The purpose is to improve the coating by combining the above.
In this regard, the commonly used chromium carbide spray material
Is Cr₃C₂-Type carbide (orthorhombic) or this and Cr₇C₃
It is a mixture with type carbides (trigonal or orthorhombic). This
This is the Cr used for modification in the present invention._{twenty three}C₆Type carbonization
There is a big difference in characteristics from ROM (cubic crystal). Immediately
The conventional crystal type (Cr₃C₂, Cr₇C₃) Chromium carbide is Cr
The amounts are 86.8% and 91.0%, respectively. On the other hand, Cr_{twenty three}
C₆Type chromium carbide is 94.3%, with a large proportion of Cr
It has high density and hardness. Especially, hydrogen gas and halogen
Release of metallic chromium deposited by reaction with chromium nitride
Once in contact with carbon, once Cr₃C₂, Cr₇C ₃ Is generated
Eventually, in this heat treatment atmosphere (500-1200 ℃)
Stoichiometrically stable Cr_{twenty three}C₆Will be moved to. The present invention
Is exactly this Cr_{twenty three}C₆Type chrome carbide
This is a modification of the properties of the ROM spray coating.

Chromium carbide spraying used in the present invention
As a material, Cr₃C₂Or Cr₃C ₂And Cr₇C₃A mixture of
Powder (3-60 μm) is used. In addition, the melt used in the present invention
As an injection material, it is possible to add Ni, Cr, Co, etc. to these carbides.
Each metal element is used alone or as an alloy of two or more
Even if it is added as a chromium carbide cermet
Good. The reason for using this chromium carbide cermet is
It is difficult to form a thermal spray coating with ROM alone.
Even if it is possible, the adhesion of the film is weak and it is porous.
Therefore, its original function as a chromium carbide sprayed coating is
Because it can not be demonstrated. In this respect, chromium carbide
When the element is added and used, the metal components are completely eliminated in the thermal spray heat source.
It melts and acts as a binder to make the film dense and dense.
This is because it improves wearability.

However, even if a film is formed by using the cermet thermal spraying material as described above, 0.5 to 0.5 is still contained in the film.
Porosity of about 5.0% is present, which hinders improvement in adhesion and wear resistance, so that the modification of the coating by the composite of the present invention is effective.

In the present invention, it is preferable that free carbon is contained in the chromium carbide spray material. The free carbon can be obtained by adding excess carbon when heating the metal and carbon or carbon compounds (CO, CmHn, etc.) in the production of various metal carbides.

In the present invention, the reason why it is preferable to include free carbon in the thermal spray material will be described below. That is, the free carbon and the metal component in the form of fine particles,
When the high temperature chromium carbide (Cr ₃ C ₂ , Cr ₇ C ₃ ) is contact-reacted on the thermal spray coating, the metal component immediately becomes a carbide and is strongly bonded to the thermal spray coating component, and this thermal spray coating reacts with this reaction. A new crystalline form of chromium carbide,
That is, it is covered with Cr ₂₃ C ₆ type carbides and also penetrates into the inside and into the pores to mutually bond with the chromium carbide particles (Cr ₃ C ₂ , Cr ₇ C ₃ ) forming the thermal spray coating. Together, it changes to a Cr ₂₃ C ₆ type crystal form, which acts to significantly modify the properties of the film.

Therefore, the method of modifying the thermal spray coating formed on the surface of the member will be described in more detail. The reforming process is roughly divided into the following. First, a chromium carbide-based sprayed coating is formed on the surface of a substrate (member) to be treated by using a combustion flame of plasma or a combustible gas. Next, the chromium carbide sprayed coating is subjected to heat treatment for reforming the sprayed coating in a gas atmosphere containing hydrogen and chromium halide at 500 to 1200 ° C.

When the above heat treatment is carried out, the vapor of hydrogen and chromium halide react with each other to generate fine activated metal Cr of 0.1 μm or less. CrX ₂ + H ₂ → Cr + 2HX (1) Here; X is a halogen element (for example, Cl, F, Br, I). Fine particles of activated metal Cr generated by the above formula (1) are deposited on the thermal spray coating. As a result, precipitated activated metal Cr
While covering the thermal spray coating, it also enters the inside of the coating mainly through the pores formed in the coating, and is filled in the pores. Furthermore, when these pores penetrate the coating, they reach the surface of the substrate to be treated,
It is metallurgically bonded to this metal base material and alloyed to enhance the adhesion.

The metallic Cr generated during this reaction reacts with the chromium carbide sprayed coating or the free carbon contained therein in a high temperature atmosphere and is the most thermodynamically stable Cr ₂₃ C _6. Form type chromium carbide.

As a result, the chromium carbide-based thermal spray coating is covered with this Cr ₂₃ C ₆ type carbide, and at the same time,
While penetrating into the surface layer of the coating to form a modified layer, it further penetrates into the pores of the coating to form Cr ₂₃ C ₆ type carbides and fills the pores to eliminate the pores. Therefore, the adhesion between the substrate to be treated and the thermal spray coating is improved, the hardness is increased due to the formation of new Cr ₂₃ C ₆ type carbide, and the chromium carbide thermal spray coating is compounded and modified,
Its properties will be significantly improved.

FIG. 1 shows a sectional structure of a member according to the present invention. (A) in the figure shows a state in which a chromium carbide cermet coating 2 is formed on a metallic substrate 1 such as steel or a superalloy by a thermal spraying method. (B) in the figure is (A)
2 is a cross-sectional structure after being brought into contact with the film of No. 1 and vapor of chromium halide containing high-temperature hydrogen gas. The fine metal chromium 3 deposited in the chromium halide gas atmosphere penetrates into the interior through the pores 4 of the thermal spray coating 2 and reacts with the base material 1 to form the alloy layer 5 and bond metallurgically. . On the other hand, on the surface of the sprayed coating 2, fine metal Cr adheres and reacts with the chromium carbide component or free carbon contained therein to produce Cr ₂₃ C ₆ type chromium carbide 6.

The above-mentioned modification treatment may be carried out by another method which produces substantially such an atmosphere, for example, a method of burying in a penetrant made of a mixture of chromium powder and ammonium chloride and heat-treating. When the modifying treatment using such a penetrant is performed, the following chemical reaction occurs in the penetrant. That is, the ammonium chloride in the penetrant decomposes to generate hydrogen chloride gas. NH ₄ Cl → NH ₃ + HCl (2) Next, HCl reacts with Cr powder in the penetrant to produce CrCl ₂ . 2HCl + Cr → CrCl ₂ + H ₂ (3) Further, this CrCl ₂ is introduced separately from the outside of the processing container as H ₂
It is reduced by the gas and fine particles of metallic chromium are deposited in the atmosphere. CrCl ₂ + H ₂ → Cr + 2HCl (4) Although the precipitation of Cr also occurs due to the reverse reaction of equation (3), if the amount of H ₂ gas supplied from the outside increases, the reaction of equation (4) takes precedence. Occurs, and the atmosphere is maintained in a reducing state, so the Cr precipitated in Eq. (4) becomes very active. Therefore, if the fine particles of Cr deposited by the formula (4) adhere to the surface of the chromium carbide sprayed coating containing free carbon, the following
According to the formula (5), it immediately reacts with free carbon to produce Cr ₂₃ C ₆ . _{23Cr + 6C → Cr 23 C 6} ... (5)

Further, in the present invention, even if free carbon is not contained in the chromium carbide sprayed coating, instead of this free carbon or together with this free carbon, "a metal carbide having a weaker carbon affinity than Cr" ( Carbide that will supply free carbon by the reaction) may be incorporated into the thermal spray coating to perform modification by compounding the carbide-based thermal spray coating. Examples of the metal carbide having a weaker carbon affinity than Cr include MnC, FeC, NiC, CoC, SiC, WC, and C.
eC, SmC, CaC, SrC, MoC, MgC, BC can be used. When so-called such a carbide is contained in the thermal spray coating, it reacts with the fine metal Cr fine particles generated by the reaction of the above formula (1) as shown in the following formula (6), and in the same manner as described above. It is possible to generate Cr ₂₃ C ₆ type chromium carbide. _{6MC + 23Cr → Cr 23 C 6} + 6M ... (6) here, MC indicates a weak metal carbides of carbon affinity than Cr.

Next, it is practical that the above heat treatment is carried out at a reaction temperature with hydrogen of 500 to 1200 ° C., more preferably 600 to 1000 ° C. Below 500 ℃, the reaction of formula (1) is slow,
On the other hand, if the temperature exceeds 1200 ° C., the mechanical deterioration of the metal material forming the base of the thermal spray coating becomes severe.

The amount of free carbon contained in the chromium carbide sprayed coating is preferably 0.01 to 5 wt%. The reason is 0.01wt
%, The amount of Cr ₂₃ C ₆ produced is small, and if it is 5 wt% or more, not only is it difficult to apply the chromium carbide sprayed coating, but also the film quality deteriorates.

Further, the content of carbide of a metal having a carbon affinity lower than that of Cr is preferably in the range of 0.1 to 100 wt%,
Within this range, the present invention can be applied regardless of the presence or absence of the above free carbon.

As a method of spraying the above-mentioned chromium carbide or chromium carbide cermet on the surface of the base material, a thermal spraying method of any heat source of plasma or a combustion flame of a combustible gas may be used, and further, an explosive thermal spraying method or a physical vapor deposition method A chemical vapor deposition method or the like can also be applied.

The thickness of the sprayed coating for spraying chromium carbide on the surface of the substrate is preferably 10 to 2000 μm, particularly 30
~ 500 μm is preferred. If it is thinner than 10 μm, the effect of modification is poor, and if it is thicker than 2000 μm, the production cost increases and it is economically disadvantageous.

In the present invention, the thickness of the Cr ₂₃ C ₆ type chromium carbide modified layer is practically in the range of 1 to 30 μm.
If the thickness is less than 1 μm, the effect of the modified layer is poor. On the other hand, if the thickness is more than 30 μm, the effect of the modified layer is not so different, and the heat treatment requires a long time, which is not economical. To be done.

The heat treatment atmosphere for forming the Cr ₂₃ C ₆ type chromium carbide reforming layer is optimally such that the mixing ratio of chromium halide vapor and hydrogen gas is 50:50 (1: 1) in terms of molar ratio. However, if the molar ratio is in the range of 80:20 (4: 1) to 20:80 (1: 4), it can be industrially used. 80:20 (4:
1) to 20:80 (1: 4) When the molar ratio is larger or smaller than the above, the amount of Cr precipitated by the hydrogen reduction reaction in the atmosphere is very small, so that Cr ₂₃ C ₆
This is unsuitable because the generation of the modified chromium carbide modified layer is reduced.

[0033]

【Example】

Example 1 In this example, in order to investigate the atmospheric gas composition for modifying a part (surface layer) of a chromium carbide sprayed coating containing Cr ₃ C ₂ as a main component into Cr ₂₃ C ₆ type carbide, Experiments were carried out using the device shown in FIG. In FIG. 2, 21 is a Ni-based alloy processing container, 22 is a chromium halide vapor introduction pipe, 23 is an argon gas introduction pipe, 24 is a hydrogen gas introduction pipe, and 25 is a gas discharge pipe. Is equipped with valves 2v, 3v, 4v that can adjust gas supply or discharge. The entire processing container 1 is placed in an electric furnace and heated from the outside, and 26 is a tube for measuring the temperature inside the processing container. Reference numeral 27 denotes an object to be processed, which can be installed on a porous alumina sintered plate 28. The test pieces of the chromium carbide sprayed coating used in this experiment, the type of processing gas, the processing temperature, and the processing time are as follows.

(1) Test sprayed coating A test piece of SUS 304 steel (50 mm × 100 mm × 5 mmt) was coated with the following chromium carbide sprayed materials by plasma spraying so as to have a film thickness of 150 μm. _{72.7wt% Cr 3 C 2 -20wt%} Cr-7wt% Ni- 0.3wt% C 69.8wt% Cr 3 C 2 -30wt% Cr- 0.2wt% C 92.8wt% Cr 3 C 2 - 7wt% Cr 7 C 3 − 0.2wt% C (2) Type of processing gas Chromium chloride vapor only (CrCl ₂ vapor pressure 47mmHg ≒ 6.266
(× 10 ³ Pa) Mixed gas in which hydrogen gas is added to chromium chloride vapor in an equivalent amount (3) Treatment temperature / time 1100 ° C × 5 hr (4) Evaluation method The surface of the sprayed coating before and after treatment was analyzed by X-ray diffraction and microscopic analysis. The microhardness was measured with a Vickers hardness meter to compare the modification effects.

(5) Consideration of test results Table 1 shows the test results. Shown in this table
As is clear from the results, the tested chromium carbide spray coating
Before the heat treatment, oxidizes in a high-temperature spray heat source.
Done Cr₂O₃The main component of the thermal spray powder material, including
It exists as it is. However, 72.7wt% Cr₃C₂
-20wt% Cr-7wt% Ni-0.3wt% C and 69.8wt% Cr₃
C₂-30wt% Cr-0.2wt% C
(Test piece No. 1, 2, 4, 5), Cr in a high temperature heat source₃C
₂Of Cr seems to have been altered ₂O₃Is newly generated
It is recognized that there is. Also these chrome carbide sprayed skins
Membrane CrCl without hydrogen₂When treated in steam only
(Test piece Nos. 4, 5, 6) are the X-ray diffraction components before treatment.
It was confirmed as it was. And the micro hardness is 760 ~
It is distributed in the range of 890mHv, but before and after the treatment
No change is observed. That is, Cr that does not contain hydrogen
Cl₂With steam alone, there is no Cr precipitation, and
It can be seen that the flame sprayed coating has hardly changed (modified).
Light

On the other hand, when H ₂ gas was contained in the CrCl ₂ vapor (test pieces No. 1, 2, 3), the surface of the sprayed coating was
Almost all of them are transformed into Cr ₂₃ C ₆ and the micro hardness is 1020.
Hardened to ~ 1280 mHv, it was found to have improved crystallographic and mechanical properties. The reason for this is that in the hydrogen-containing gas chromium chloride vapor, a minute active metal Cr is deposited in the gas phase by the chemical reaction of Eq. (7), adheres to the surface of the thermal spray coating, and then adheres to this active metal Cr. Is due to the reaction with free carbon contained in the thermal spray coating to produce Cr ₂₃ C ₆ type chromium carbide. CrCl ₂ + H ₂ → Cr + 2HCl (7)

[0037]

[Table 1]

Example 2 In this example, the amount of free carbon contained in the chromium carbide sprayed coating and the change to Cr ₂₃ C ₆ were investigated using the apparatus shown in FIG. In FIG. 3, 31 is a Ni-based alloy processing container, 32 is a hydrogen gas introduction pipe, 33 is a gas discharge pipe, and 34 is a gas discharge pipe.
Is a temperature measuring tube in the processing container, 35 is an object to be treated (sprayed coating test piece), 36 is a penetrant, chromium powder 70 wt%, alumina 29 wt
%, Ammonium chloride 1.0 wt% composition.

2-1 Test spray coating (a test piece having the same dimensions as in Example 1 was applied to a thickness of 150 μm by the plasma spray method) 73 wt% Cr ₃ C ₂ -20 wt% Cr-7 wt% Ni 72.99 wt% Cr _{3 C 2 -20wt% Cr- 7wt% Ni-} 0.01 wt%
_{C 72.5wt% Cr 3 C 2 -19wt} % Cr- 8wt% Ni- 0.5wt% C 67wt% Cr 3 C 2 -21wt% Cr- 7wt% Ni- 5wt% C 2-2 method of modification treatment A: chloride Installed in a gas atmosphere in which hydrogen gas is added to chromium vapor in an equivalent amount (Fig. 2), 11000 ° C x 5 hrs B: chromium powder (70 wt%) + alumina powder (20 wt%) +
Immersed in a penetrant consisting of ammonium chloride (10 wt%) (Fig. 3), 1100 ° C x 10 hr 2-3 Evaluation method Same as Example 1 Table 2 shows the above test results. As is clear from this result, Cr ₂ O ₃ was observed before treatment in the chromium carbide sprayed coating containing no free carbon (test piece No. 1).
(Produced in the thermal spraying heat source) disappeared, but a small amount of Cr and Cr ₂₃ C ₆ was also produced along with Cr ₃ C ₂ and free carbon (0.01 wt.
It can be seen that the change from Cr ₃ C ₂ to Cr ₂₃ C ₆ is made even if it does not contain (% or less). However, since the amount of Cr ₂₃ C ₆ produced is small, the hardness of the sprayed coating after the treatment is relatively small, but it is considered that the densification of the sprayed coating and the improvement of the adhesion can be expected sufficiently.

On the other hand, a thermal spray coating containing 0.01 wt% of free carbon
In (Test piece No. 2), clear Cr_{twenty three}C₆The peak of
In addition, the micro hardness exceeds 1000 mHv and the film is completely
It was found to have been modified. In addition, free carbon 5wt
% Sprayed coating (No. 4) also contains Cr_{twenty three}C₆Peak and microhard
1050 to 1280 mHv, so release in the spray coating
When the amount of carbon is in the range of 0.01 to 5 wt%, the modified film of the present invention is obtained.
Was confirmed. A thermal spray coating that does not contain free carbon
Initially recognized in Cr₂O₃(Cr in the thermal spray heat source ₃O₂Part of
(Oxidized product) disappeared after the treatment.
It is considered that the element reduced it to Cr.

[0041]

[Table 2]

Example 3 (Improvement of Corrosion Resistance by Eliminating Porosity of Sprayed Coating) The sprayed coating obtained by spraying in the air always contains pores, which causes the deterioration of corrosion resistance. Is well known. Considering the manufacturing process and mechanism of the modified thermal spray coating used in the present invention, it has an action of eliminating pores in the thermal spray coating. In order to confirm this, the following experiment was conducted to confirm the existence of the sealing function.

In other words, in this embodiment, mild steel (SS 4
00) test piece (50 × 100 × 5mmt) was coated with a carbide cermet spray coating on one side by plasma spraying and high-speed flame spraying to a thickness of 150 μm, and this was applied using the apparatus in FIG. 3 at 930 ° C × 10hrs. Was heat-treated to produce the modified thermal spray coating used in the present invention. Thereafter, the modified sprayed coating thus produced was subjected to a salt spray test according to JIS Z 2371 (1988) to determine the effect of sealing from the state of formation of red rust generated from the pores of the coating. (1) Test spray coating 73wt% Cr ₃ C ₂ -20wt% Cr-7wt% Ni 62wt% Cr ₃ C ₂ -11wt% Cr ₇ C ₃ -18wt% Cr-9wt% Ni The cross section of the film is observed with an optical microscope and a scanning electron microscope before the test,
The porosity was calculated from the pore area occupied in the visual field.

Table 3 shows the results of the appearance observation of the film observed 24 hours and 96 hours after the start of the salt spray test. As is clear from the test results, in the coatings of Comparative Examples (Nos. 7 and 8), red rust had already formed after 24 hours, and after 96 hours, 8 to 15% of the coating area was covered with red rust. Was there. That is, salt water flows into the interior through the pores of the film, corrodes the mild steel of the base material, and the corrosion products are red rust and are jetted onto the surface of the film. Large plasma spray coating (No.
7) was more prominent.

On the other hand, in the modified thermal spray coating used in the present invention (Nos. 1 to 6), no red rust was observed at all even after 96 hours, and it was confirmed that it was in a healthy state.
It is considered that this is because, when the heat treatment is performed in a chromium halide gas containing hydrogen gas, the fine particles of metal Cr deposited in the atmosphere fill the pores of the film and prevent the intrusion of salt water. From the above results, the modified thermal spray coating used in the present invention eliminates the pores of the coating, and since it is performed by the metal Cr particles, it has a much higher temperature than conventional organic sealing agents. It can be seen that it can be used in.

[0046]

[Table 3]

Example 4 (Enhancement of thermal shock resistance by improving adhesion of thermal spray coating) A chromium carbide cermet coating of 150 μm was formed on one surface of a SUS304 steel test piece (50 × 100 × 5 mmt) by a plasma spraying method.
After constructing it to a thick thickness, use the equipment shown in Fig. 3 to make it 930 ℃ ×
The modified thermal spray coated member according to the present invention was manufactured by performing a heat treatment for 10 hrs. Then, this thermal spray coating member was allowed to stand in an electric furnace maintained at 1000 ° C. for 15 minutes and then placed in water at 25 ° C. to repeat the thermal shock operation, and the state of film peeling was observed.
For comparison, a thermal shock test was performed on the carbide cermet sprayed coating not subjected to the heat treatment under the same conditions. (1) Test spray coating 73wt% Cr ₃ C ₂ -20wt% Cr-7wt% Ni 62wt% Cr ₃ C ₂ -11wt% Cr ₇ C ₃ -18wt% Cr-9wt% Ni

Table 4 shows the results of the above thermal shock test. The thermal spray coating of the comparative example that was not heat treated (No.
3, 4) and 12 to 14 times were repeated, and a part of the film began to peel off, and 40 to 50% of the film fell off after 15 times. On the other hand, the modified thermal spray coating used in the present invention (No. 1, 2)
It was confirmed that, although the surface of the coating changed to green, the coating did not peel off even after repeated 20 times, maintained a healthy state, and had a strong resistance to thermal shock.

[0049]

[Table 4]

Example 5 In this example, the change in the thickness of the Cr ₂₃ C ₆ type chromium carbide reforming layer produced when the molar ratio of chromium chloride vapor and hydrogen gas was changed was investigated. (1) The test sprayed coating used had the following composition (a test piece having the same dimensions as in Example 1 was applied to a thickness of 150 μm by the plasma spraying method). 72.7 wt% TiC-19 wt% Cr-8 wt% Ni-0.5 wt% C (2) Condition of reforming treatment Change the molar ratio of chromium chloride vapor and hydrogen gas within the range of 5/95 to 95/5, 1100 ℃ × 16hrs,
Using the apparatus shown in FIG. 3, the reforming treatment was performed under the conditions of 500 ° C. × 16 hrs. In the apparatus shown in FIG. 2, additional treatment was performed under the conditions of 1200 ° C. × 16 hrs with a molar ratio of chromium chloride vapor and hydrogen gas of 50/50. (3) Evaluation method from the surface of the thermal spray coating to an internal diffusion coating with fine metallic chromium by modifying the thickness of the resulting Cr ₂₃ C ₆ layers was measured and confirmed by X-ray diffraction.

(4) Evaluation Results FIG. 4 shows the above experimental results. As is clear from this result, a relatively thick modified layer can be obtained by the treatment at 1100 ° C x 16hrs, but it is extremely thin at 500 ° C.
It can be seen that the thickness is 2 μm. Furthermore, when the contents were examined in detail, the thickness of the modified layer was maximum when the CrCl ₂ / H ₂ molar ratio was 50/50 (1/1) at any treatment temperature, and the molar ratio was The thickness of the modified layer tends to decrease regardless of the direction of ₂ <H ₂ , CrCl ₂ > H ₂ . This is because the amount of Cr deposited in the vapor phase changes depending on the change in the molar ratio of CrCl ₂ and H ₂ . Since the thickness of the modified layer of the present invention needs to be at least 1 μm, the CrCl ₂ / H ₂ molar ratio for ensuring the thickness of 1 μm at the processing condition of 500 ° C. is 80/20 (4/1) to 20. It was confirmed to be in the range of / 80 (1/4). The CrCl ₂ / H ₂ molar ratio is 50/50,
The thickness of the modified layer of the carbide sprayed coating, which was carried out at 1200 ° C. × 16 hrs, was 30 μm at the maximum.

[0052]

As described above, according to the present invention,
Cr ₃ C ₂ , Cr ₇ C ₃ type thermal spray coating containing chromium carbide, or
Activated metal Cr by heat-treating a chromium carbide sprayed coating containing a carbide of a metal having a carbon affinity lower than that of Cr in a chromium halide forming atmosphere containing hydrogen gas.
Since it is possible to deposit the fine particles of, it is possible to form Cr ₂₃ C ₆ type carbides on the surface and in the pores to form a composite by acting this on at least the surface of the thermal spray coating, so chromium carbide spraying The surface layer of the coating can be modified. Moreover, this modified thermal spray coating greatly contributes to the improvement of corrosion resistance due to the disappearance of pores, the improvement of wear resistance due to the increase of the microhardness of the coating due to the formation of Cr ₂₃ C ₆ , and the improvement of erosion resistance. is there.

[Brief description of drawings]

1A and 1B are cross-sectional views of a sprayed coating before and after a modification treatment.

FIG. 2 is a schematic diagram of a reforming treatment apparatus used in Example 1.

FIG. 3 is a schematic diagram of a reforming treatment apparatus used in Example 2.

FIG. 4 is a diagram showing the relationship between the molar ratio of CrCl ₂ gas and H ₂ gas and the thickness of the layer modified to Cr ₂₃ C ₆ type carbide.

[Explanation of symbols]

1 Base Material 2 Chromium Carbide Cermet Thermal Spray Coating 3 Activated Metal Chromium Fine Particles 4 Coating Porosity 5 Alloy Layer with Base Metal 6 Cr ₂₃ C ₆ Type Chromium Carbide Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisamu Nagahara 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Inside the EBARA CORPORATION (72) Masamichi Kawasaki 11-11 Haneda-Asahi-cho, Ota-ku, Tokyo (72) Inventor Yoshio Harada, 4-13-4 Fukaekita-cho, Higashinada-ku, Kobe-shi, Hyogo Prefecture Tokaro Co., Ltd. (72) Inventor Junichi Takeuchi 4--13-4, Fukaekita-cho, Higashinada-ku, Kobe, Hyogo Prefecture Tokaro Within the corporation

Claims (6)

[Claims] 1. A modified layer comprising a base material and a chromium carbide sprayed coating formed on the surface of the chromium carbide sprayed coating, at least the surface layer of which is deposited and impregnated with Cr ₂₃ C ₆ type chromium carbide. A chromium carbide spray-coated member characterized by being formed by: 2. The carbide constituting the chromium carbide sprayed coating formed on the surface of the base material is Cr ₃ C ₂ or Cr ₃ C ₂ and Cr ₇ C ₃
2. The chromium carbide spray-coated member according to claim 1, which contains a mixture thereof. 3. The above-mentioned carbide-based sprayed coating contains Cr ₃ C ₂ , Cr ₇ C ₃ carbide containing no free carbon or at least 0.01 to 5 wt% of free carbon or chromium as a coating component. Carbide of metal with weak carbon affinity 0.1 ~
The chromium carbide spray-coated member according to claim 1 or 2, which contains 100 wt%. 4. The Cr ₂₃ C ₆ type chromium carbide modified layer is chemically active by heat-treating the chromium carbide sprayed coating at 500 to 1200 ° C. in a chromium halide-containing atmosphere containing hydrogen gas. The chromium carbide spray-coated member according to claim 1, which is formed by depositing fine metallic chromium and adhering it to the surface of the spray coating to impregnate it. 5. The Cr ₂₃ C ₆ type chromium carbide reforming layer has a mixture ratio of hydrogen gas and chromium halide gas of 1/4 to 4/1 in the reaction tank of the chromium carbide sprayed coating. While controlling the temperature as described above, a chemically active fine metallic chromium is deposited by heat treatment in a heating atmosphere of 500 to 1200 ° C, and this is adhered and impregnated on the surface of the thermal spray coating, and the diffusion penetration thickness is 1 The chromium carbide spray-coated member according to claim 1, wherein the chromium carbide spray-coated member is formed so as to have a thickness of -30 μm. 6. The chromium carbide sprayed coating formed on the surface of the base material is selected from among carbides made of Cr ₃ C ₂ or a mixture of Cr ₃ C ₂ and Cr ₇ C _3, and Ni, Cr and Co. 2. The chromium carbide spray-coated member according to claim 1, which is formed by spraying a carbide cermet composed of at least one kind of metal described above.