JPS63286566A - Method for adhering diffused carbide coating substance to iron-carbon alloy product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF APPLICATION OF THE INVENTION The present invention relates to metallurgy, thermochemical processing of metals and alloys, and more particularly iron-carbon alloy products.
diffused carbide coating (alloy articles)
11 difru, 5ion carbide c
oatings)
g) Pertaining to the method of enforcement.

In order to extend the durability and service life of mechanical parts and type 1 parts that are subjected to severe wear, they can be diffusion saturated and thus coated with a diffusion coating (DI) on the surfaces of these parts.
fusion coating). This coating should be characterized by higher hardness and wear resistance than in the material of the product. These requirements are most fully met by carbide type diffusion coatings.

Prior Art One of the most common methods of depositing metal carbide coatings on various products, including those made from iron-carbon alloys, is chemical deposition of the carbide from the vapor phase (chemical vapor deposition). “Plansee”
” (Austria), Berna AG (Austria)
AG)” (Switzerland), “Concerc” (USA)
, Scientific Coating
s Inc,) (USA), Troy (USA), PED Ltd,
) (UK), Coleshill (UK), “Sandvic” (Sweden), etc. The equipment for depositing carbide and other types of coatings includes a wide variety of By introducing modular equipment and increasing the active volume of the reaction vessel, a highly efficient process is ensured.
By depositing a chromium carbide coating of a mixture of these carbides on a steel tool, it is possible to use the tool at temperatures up to 950 DEG C. and the service life of the tool is increased by 20-25 times. A carbide layer is produced on the heated surface of the product due to the chemical interaction of chromium halides and methane. Place the product in the reaction vessel, apply vacuum, heat, and once the temperature rises to 850-1050 °C,
A gaseous mixture of chromium halide, methane (CH4) and carrier gas is introduced into the reaction vessel.

The carbide layer thickness up to 121 JII ensures high wear resistance. A carbide layer thickness of more than 12111 mm is required in some cases for better working and tribological properties of the product, but this thickness is This results in decarburization of the layer of a certain substrate, which has a negative effect on the properties.Moreover, in the above steps of depositing the carbide coating, the growth rate of the carbide layer generally does not exceed 2 pi/h; This increases the growth time.

The coating of chromium carbide Cr 7 C3 is deposited at a fairly high rate and at low temperature by decomposition of bis-ethylbenzene vapor on the heated surface of the workpiece in vacuum. To prevent the formation of dendrites within the coating,
The process is carried out under non-isothermal conditions.
condition), that is, in the first stage, 1
300-350°C for 0 minutes then 500-350°C for 50 minutes
0 working chamber (working at 600℃)
The pressure inside the chamber is 1.33 Pa. The thickness of the chromium carbide layer deposited in this method is 340u
z, this layer is characterized by high abrasion resistance and micro hardness of 250 ONV. However, overcast coverings have a high dead load (s
specific loads), especially alternating loads (at
ternative 1oads) and under significant tangential stresses. This is because this leads to delamination of the carbide layer due to the low adhesion strength at the interface with the base metal.

Chromium carbide coatings deposited at higher temperatures are of interest because of their significantly higher bond strength to the base metal. One of the prior art methods is to use 5-20% HNO,
and a pretreatment of the surfaces of the workpieces with a solution containing 10% fluoride and then coating these surfaces with a suspension based on chromium powder. This suspension is prepared from a solution of an organic binder, such as an acrylic resin, in a solvent such as methyl chloroform. By the way, diffusion coating involves immersing the workpiece in a retort filled with a powder mixture and then applying argon or hydrogen for 2 to 30 minutes.
Deposited by passing at 900-950°C for 10 hours. However, this technique is rarely productive, labor-intensive, and the use of volatile organic compounds requires extra labor consumption and environmental protection (US Pat. No. 4,347,267). No., IPCBO5
D 7/22, DO5D 7/14, NPC427
/237. Published August 31, 1982).

The amount of labor required to deposit a diffused chromium carbide coating can be significantly reduced by heating the surface with a stream of HF. A saturated mixture containing chromium and halogen-containing compounds is sprinkled freely over the treated surface.

The equipment used in this process includes a water-cooled inductor and, if necessary, a separator made of non-metallic material. This method is economical due to the localization of the heating surface and the possibility of recycling the material utilized for the application of the coating. At the same time, the carbide coating deposited in this way is non-uniform with respect to thickness, chemical composition and phase composition, since the heating of the workpiece by the HF stream does not allow for a uniform temperature distribution over the treated surface. It should be pointed out that (UK Patent Application No. 2109822, IPCC 23C9102, published 8 June 1983).

All of the above methods require that during subsequent operation of the coated product,
It is noteworthy that this leads to decarburization of the lower zone which reduces the permissible contact pressure against the reinforced surface.

This is due to the diffusion of carbon contained in the iron-carbon alloy into the layer of deposited carbide-forming elements that form carbides.

In order to reduce or eliminate the decarburization effects of the lower zone as a whole, it is common practice to presaturate the surface layer in two stages, i.e., to presaturate the surface layer with carbon or nitrogen, and then to saturate it by depositing carbide-forming elements. It has been implemented. Carbon or nitrogen introduced into the surface layer in the first stage is converted into carbides, nitrides or carbonitrides in the second stage.
ide), thus preventing decarburization of the lower zone.

A method for applying a chromium carbide-based diffusion coating to the surface of steel products containing at least 0.2% carbon is patented in the United States.

Pre fine nitriding to a depth of 100-350 uz for 5-40 hours at 450-650 °C in an atmosphere of nitrogen-hydrogen mixture.
nitriding) to add 1 in the nitrided layer.
．． 5-2.5% nitrogen is produced. The second step of the method consists of open gas chromizing (xpowa) at 850-1100°C for 5-30 hours.
In this second stage, the resulting layer of chromium carbide is up to 40 μl thick and is characterized by high wear resistance. It should be noted that such a coating deposition process is very long, requires considerable power consumption, and cannot be considered a very efficient process (1980).
U.S. Patent No. 4,242,151, I, issued December 30,
PCC23C11104, 11/16).

In a reducing atmosphere based on hydrogen, ferrochrome, 0.4-1
．． 0% ammonium chloride and chromium (50-75%
) is known in the prior art. While processing steel products containing more than 0.35% carbon, 0.5-1.5% ammonium fluoride is added to the chromium plating mixture. The necessity of using a hydrogen atmosphere during heating reduces the economics of such a process and requires the provision of special fire and explosion precautions (French Patent Application No. 1/18 2439824, C1, C23F
17100. Published May 23, 1980; French Patent No. 2483468, CI, C23C9100,
(Released on December 4, 1981).

In the first step of the process, in molten nitrate medium, about 4
A similar result is achieved by G4 by performing submerged nitriding at 00-800° C. for 12-150 hours (French patent application no. 24544), which clearly reduces the process efficiency.
No. 71, C1, C23C11104, 11/14.19
(Released on November 14, 1980).

In the first stage of the process it is also possible to use carburizing, polonizing or sulfurizing; the chromium carbide coatings produced in this way have high wear resistance.

In some cases, a nitriding or carburizing step in a liquid or gaseous medium is performed after depositing a layer of carbide or nitride-forming elements on the treated surface. Carbide, nitride or carbonitride layers are also characterized by high wear resistance, but the adhesive strength of such coatings is substantially lower than in the case of previous coatings (East German Patent No. 2).
No. 005730, IPCC23F 17100.19
(Public announcement on May 18, 1983).

However, a two-step process consisting of sequential operations such as saturation of the workpiece surface layer with carbon, nitrogen or boron and deposition of carbide- or nitride-forming elements, in either order, improves the overall economic and technical parameters of the process. As it worsens, it requires a very long period of time.

Rapid formation of carbide layers in steel products can also be achieved by diffusion saturation within the antimony melt with alloying additive particles containing carbide-forming elements such as chromium. The workpiece is immersed in the melt, heated to 1090°C and held for 5 hours.

This involves the migration of atoms of the alloying elements to the workpiece surface and subsequent diffusion into the product material [Gene Wolfe Breakthrough in Diffusion Alloying].
in diffusion alloying),
“Plant Engineering
FIineering)'' (USA), 1976.30.
No. 25, p.

127-128], yet such a technical process cannot be considered universal and promising from an economic point of view.

Production method of diffusion carbide coating developed in Japan [
“Toyota-Diffusion
” is a combination of sufficiently high production capacity and suitability for production. Melts of anhydrous borax (NaxB40t), anhydrous boric acid or boron oxide (B 20 s > or the compound K 2 B 40 r) The workpiece is placed in a crucible filled with the borax melt containing 1-60% of these alloying carbide-forming elements in the form of finely divided compounds, depending on the desired composition of the carbide coating. alloyin
g carbide-forming ele+5en
ts). The content of carbide-forming compounds is 30%
The borax content should be above. The functions of carbide-forming elements include chromium and V of Mendeleev's periodic law.
This may also be accomplished by group A metals, namely vanadium, niobium and tantalum.

Compounds of these elements may be used in the form of ferroalloys or oxides (US Pat. No. 4158'578, IPCC 23C9/
10. Published June 19, 1979), in the form of chromium or its alloys as oxides and pure metals in a mass relationship of boron and oxides within 7-40% (U.S. Pat.
No. 230751, IPCC23C9/16, C25D
3/66. Issued October 28, 1980; U.S. Patent No. 4,202,705, IPCC 23C9/10.1980
(issued on May 13, 2017).

This process is carried out at 850-1100°C within 1-20 hours. Although the coating produced in this way has a high wear resistance, this method requires a subsequent finishing of the workpiece surface and, moreover, The surface of such products after application of the coating is necessarily oxidized and often
Additional machining is required to give the product the required surface roughness.

Problems to be Solved by the Invention It is an object of the present invention to deposit, precipitate, deposit, etc. a diffusion carbide coating on an iron-carbon alloy product.
To provide a method for improving the physico-mechanical properties of coatings and, in particular, improving the hardness and abrasion resistance, thereby increasing the service life of the product. be.

Means for Solving the Problem The above problem is solved by charging a powder mixture containing one solid component, a carbide-forming element, a carbon-bearing compound, an activator, an inert filler, into a container, and immersing iron-carbon alloy products in; - heating the products to the carburizing temperature of their surfaces; - carrying out carburization of the product surfaces; - carburizing the products so that their product surfaces are saturated with carbide-forming elements; Heat to temperature; -950 to 1100
According to the invention, in a method for depositing a diffusion carbide coating on an iron-carbon alloy product comprising diffusion saturating the product surface with carbide-forming elements at a temperature in the range of carburization occurs within a period selected from 0.6 to 1.2 hours at a temperature in the range of 560-720 °C; - heating the carburized product to the temperature of diffusion saturation;
carried out at a temperature selected from the range 0 to 1100 °C and at a rate varying from 0.8 to 2.4 degrees per second (°/s); - diffusion saturation of the workpiece surface by carbide-forming elements is 950 °C;
occur within a period of 1.2 to 1.8 hours at temperatures between speed, 300-50
A diffusion carbide coating is applied onto an iron-carbon alloy product, characterized in that the above operation is repeated at least once, starting with heating one product to the carburizing temperature; solved by providing a way to attach.

The above operation is repeated up to seven times in order to deposit a diffused carbide coating which gives the product maximum surface hardness and abrasion resistance.

DETAILED DESCRIPTION OF THE INVENTION A detailed description of the method for depositing diffusion carbide coatings on iron-carbon alloy products is provided below.

The deposition of diffusion carbide coatings onto iron-carbon alloy products is achieved by catalytic deposition from the gas phase within a powder mixture consisting of carburization of the product surface, followed by diffusion saturation with carbide-forming elements.
act position). The powder mixture in this method should contain the following solid components: carbide-forming elements, carbon-containing compounds, activators and inert fillers. The carbide-forming elements may be constituted by chromium, molybdenum, tungsten, niobium, zirconium, tantalum, silicon or mixtures thereof. The carbon-containing compound may be diphenyl, naphthalene, anthracene, pyrene, triphenylene, 3,4-benzopyrene; in addition to the organic compounds mentioned above, other solid organic compounds of the hydrocarbon class may be used; The organic compound should be in a solid state at room temperature and its boiling point or sublimation temperature ranges from 100 to 700°C. The function of activator may be performed by ammonium chloride, ammonium fluoride, ammonium iodide, ammonium bromide, aluminum oxide, magnesium oxide or silicon dioxide may be used for inert fillers. .

A powder mixture consists of a total of 50% of the ingredients taken separately in powder form.
It is prepared by sieving through a vibrating sieve with a mesh size of 1z or less. The particle size of the sieved part is 50
With particles of this size, which should not exceed μm,
A high degree of saturation of the surface with carbon in the carburizing stage and with carbide-forming elements in the diffusion saturation stage is ensured. Moreover, using a powder mixture with particles of this particle size, the adhesion of the mixture particles to the surface of the workpiece (st
icking) is prevented. After sieving, each component is weighed out in the following mass percentages.

Carbide-forming elements 40-70 Carbon-containing compounds 0.5-2.5 activity
Agent 0.2-5. 0 Inert filler After weighing the remaining amount, each component of the powder mixture is added, depending on the nature of the component.
Dry under constant conditions. The carbide-forming element powder is 14
Dry for 4 hours at 0°C. The inert filler powder is
Calcinate at 1200°C for 2 hours. Carbon-containing compounds are 6
Dry within 0.5-1.0 hours at 0°C. The activator powder was then dried at 140°C for 4 hours.Then, all ingredients were cooled to 40°C and placed in a bicone mixer for 1-4 hours.
Mix thoroughly for 2 hours.

Moisture content in powder mixtures intended for use in the preparation process of diffusion carbide coatings
(ten) should not exceed 5-6%. The powder mixture is placed in a stainless steel container, the product has a distance of at least 20 shoulders from the bottom of the container to the product;
It is immersed in the mixture such that there is a distance of 1 ozg from the side wall of the container to the container, a distance of at least 15 iv between the products, and a distance of at least 30 zz from the product to the first container cover.

After the product has been immersed in the powder mixture, the container is capped with a first stainless steel cover and a layer of silica sand at least 30zz thick is poured on top.

Next, close the second cover and add 20 degrees of boron oxide B (approximately 4
A substance with a melting temperature of 50° C.) is poured onto the top.

Place the container containing the powder mixture and product into the resistance furnace;
and heating to a temperature of 560-720° C.; then carburizing the surface of the product; according to the invention, the carburizing is carried out at a given temperature within the limits of 0.6-1.2 hours.

The mechanism of the chemical reactions that take place inside the vessel during this process can be illustrated by the example of a saturating powder mixture consisting of chromium, diphenyl, ammonium fluoride, and aluminum oxide. Aluminum oxide is an inert filler and does not participate in chemical reactions.

During heating, diphenyl starts to decompose from a temperature of about 256°C: 2 CI 2 H+ o → 5CH, +19C (1
) Carbon interacts with oxygen inside the container: C+ 0
2 → CO2 (2) Ammonium fluoride begins to decompose at a temperature of 335°C: NH,F −4NHff+HF (3)2
N H3 → N 2 + 3 Hz (4
) The saturated hydrocarbon (methane) produced during the decomposition of diphenyl then interacts with some of the hydrogen fluoride, thus producing carbon tetrafluoride. This carbon tetrafluoride is adsorbed onto the surface of the product, producing active carbon atoms that saturate the surface of the product: CH4+4HF −+ CF, +4H
2(5)CF 4+ 4 Fe →2 Fe F
2+ C(6) reactions (5) and (6) are mainly
occurs during carburization time.

When the temperature inside the furnace reaches 450°C, boron oxide B20.
It melts to form a compact scum that seals the container and prevents air from penetrating into the container along with the oxygen contained therein.

As the temperature increases to 814° C., the chromium in the vessel begins to evaporate, interacts with the hydrogen fluoride and creates an active gaseous medium for diffusion saturation.

Cr + 2 HF → Cr F 2 + H2 (
7') Chromium fluoride is adsorbed on the surface of the product to generate active chromium atoms, which diffuse into the surface layer of the product: Cr25Cs → FeFt+C(8)Cr F 2
+ H2 → 2 HF + Cr (9) The active chromium atoms interact with the carbon diffused on the surface of the product during the carburizing stage to form a diffused carbide coating: 23Cr+6C= Cr25Cs (10) Reaction (7) - (10) proceeds very aggressively at temperatures chosen from the range 950-1100°C.

Carburizing allows the surface layer of the product to be saturated with carbon that diffuses from the powder mixture into the product, thus ensuring enhanced formation of a diffused carbide layer during subsequent heating.

The diffused carbide layer is formed only by carbon that has diffused from the powder mixture to the surface of the product. The carbon contained within the material of the product does not diffuse to the surface of the product to create a carbide layer, which prevents the formation of a decarburized zone under the coating that is present in other prior art methods. impede practically.

During the carburization stage, carbon-containing compounds are decomposed to produce large amounts of gaseous saturated hydrocarbons and also some amount of carbon dioxide which is obtained by interacting with the oxygen in the air and with the steam. The hydrocarbons and carbon dioxide of
According to reactions (1) and (2), a small amount is present in the container.

The interaction of the hydrogen halide formed during the decomposition of the activator according to reaction (3) with the decomposition products of the carbon-containing component may also lead to the formation of gaseous compounds of carbon and one of the halogens, such as carbon tetrafluoride. This increases the saturation of the surface with carbon. The product is held at these temperatures to bring about saturation of the surface layer with carbon, thereby ensuring early formation of a carbide layer during subsequent heating. If the temperature and time limits mentioned above are not adhered to, the desired effect will not be achieved; carburization at temperatures below 560° C. will result in sufficient carbon diffusion from the decomposition products of the carbon-containing compounds of the mixture into the surface layer of the product. Carburizing at temperatures above 720° C., where flow is not ensured, leads to premature deposition and subsequent diffusion of carbide-forming elements on the surface of the product. If the carburization time is shorter than 0.6 hours, the carbon concentration on the product surface will decrease, causing the formation of a decarburized zone under the diffusion coating, which will reduce the strength of the product with the diffusion carbide coating. and reduce frictional properties on the palm.

If the carburizing step takes longer than 1.2 hours, this is unsuitable from an economic point of view. This is because the strength and friction properties are no longer increased and there is an unreasonable consumption of power.

Once the carburization time has expired, the product is heated to the diffusion saturation temperature. Heating is carried out at a rate selected from 0.8 to 2.4°/s. This procedure ensures a constant concentration of carbon on the surface layer of the product, saturated with carbon diffused from the powder mixture into the product during the carburization stage, and a diffusion carbide coating during the diffusion saturation stage.
The formation of decarburization zones under carbide coatings is prevented. Heating to the diffusion saturation temperature at a rate higher than 2.4'/s is impractical from an economic point of view, as it requires a large amount of energy consumed by more powerful heaters; .Heating carried out at a rate lower than 8°/s results in a diffusive dispersion of carbon from the surface layer; the carbon begins to diffuse into the product, i.e. into the matrix, thereby reducing the concentration of carbon in the surface layer. . In the diffusion saturation stage, this results in the amount of carbon diffused into the surface layer in the carburizing stage being insufficient to form a diffusion carbide layer; as a result, carbon begins to diffuse out of the steel; A decarburization zone is thereby created below the carbide layer.

Diffusion saturation temperature range from 950 to 1100°C (black
et) When the temperature reaches a certain value, stop the heating and proceed to 1.
This procedure, with diffusion saturation within a period selected from 2 to 1.8 hours, creates a diffused carbide layer on the surface of the product. The formation of the diffused carbide layer is ensured by the interaction of the carbide-forming elements adhering to the surface with the carbon that has saturated the surface layer of the product according to reaction (1). The carbon contained in the material of the product has, during the above-mentioned time period, become carbon-free in the surface layer of the product, which does not actually participate in the formation of the diffused carbide layer, which prevents the formation of a decarburized zone below the diffused carbide layer. It should be noted that, being saturated, the carbide layer forms more actively than in previously known methods. If the above temperature and time intervals are not observed, the desired effect will not be obtained, as a result of the diffusion saturation carried out at temperatures below 950 °C, the thickness of the diffused carbide layer due to insufficient diffusion of the carbide-forming elements into the coating. This results in a reduction in stiffness, which reduces the strength and friction properties of the coating.

Diffusion saturation carried out at temperatures above 1100° C. is likewise unsuitable. This is because at such temperatures the size of the particles of the product material increases, thereby reducing the mechanical properties of the product, ie its impact strength. If diffusion saturation is carried out in a time shorter than 1.2 hours, insufficient deposition rate of carbide-forming elements on the surface of the product may occur.
tion rate) and the formation of a thinner diffusion-saturated layer, thereby impairing the strength and friction properties of the coating.

Conversely, extending the time of diffusion saturation beyond 1.8 hours results in the formation of a diffused carbide layer with a lower concentration of carbon. This is because under these conditions carbon diffuses through the carbide layer that was already formed and this diffusion process loses its strength due to the reduced carbon concentration in the surface layer. . Additionally, at such diffusion saturation times, carbon may diffuse from the matrix to the coating. This is because the entire amount of carbon introduced to the surface during the carburization stage would have already been used up to create the carbide layer while the diffusion of the carbide-forming elements continues. This effect causes the formation of a decarburized zone under the coating.

Once the diffusion saturation time has expired, the container containing the product is heated according to the invention to a selected temperature from 300 to 500° C. at a selected speed within the limits of 1.2 to 2.4°/s. cooled down.

This technique makes it possible to avoid the effects of carbon redistribution under the diffused carbide layer and the formation of decarburized zones under the coating. At these cooling rates, carbide-forming elements and carbon stop precipitating from the powder mixture onto the surface of the product, so that there is no diffusion of carbon from the matrix to the surface of the product.

Cooling after diffusion saturation at rates higher than 2.4°/s is not economically practical, as it requires the use of special cooling systems; conversely, at rates lower than 1.2°/s Cooling the vessel after diffusion saturation at , results in the deposition of carbide-forming elements on the surface, but the diffusion of carbon within the carbide layer, which diffuses, albeit at a lower rate, to the surface to form carbides. Redistribution occurs, creating a highly undesirable decarburization zone beneath the carbide coating.

After cooling to a temperature chosen in the range from 300 to 500° C., the entire process steps described above are repeated according to the invention for a number of cycles ranging from at least 1 to 7 times.

The number of cycles within these limits should be chosen to suit the conditions of use of the product with the diffusion coating. If the cycle is repeated 6 or 7 times, the resulting coating is characterized by high strength and tribological properties.

Upon cycling the above treatment steps by carburizing within 560-720°C, the diffused carbide layer created in the previous cycle becomes saturated with carbon from the powder mixture, and during heating thereon, the deposited carbide-forming elements are removed. It diffuses into the layer and then its carbide is formed. The circulation promotes the growth of the diffused carbide layer without reducing the concentration of carbon in the lower zone.

In addition, due to the cyclic nature of the temperature condition of saturation with periodic cooling to a temperature chosen from the interval 300-500 °C,
A diffused carbide layer with a more dispersed structure is formed. By repeating the two-step heating cycle after cooling to a temperature of 300-500°C, crystallization of carbide-forming elements on the treated surface, rather than growth of already existing carbide crystals, is achieved. This is due to the fact that new species formation and carbide development result. This produces a large number of fine carbide crystals that improve the strength and tribological properties of the product.

Completion of the cooling process at a temperature higher than 500°C results in
The possibility of the formation of new crystallization species is ruled out, so that subsequent heating and carburization only causes the growth of the existing carbide crystals, without creating a finely dispersed structure.

Completing the cooling at temperatures below 300° C. is unsuitable from an economic point of view, since this involves an extra amount of power for subsequent heating. If the number of cycles is less than 2, the concept of 'circulating process' loses its meaning. If the number of cycles is more than 8, the powder mixture becomes wasted, i.e. the product surface is removed from the powder mixture. The amount of carbon that diffuses into the carbon is reduced, resulting in longer holding times between each cycle and overall undue lengthening of the process and additional consumption of power.

Once the required number of cycles have been completed, stop heating and
Cool the container in air to room temperature. The container is then opened and the product and powder mixture removed, and the product is shipped to the customer while the saturating powder mixture is sent for recycling. Regeneration involves grinding the powder mixture in a ball mill, sieving it through a vibrating sieve (50 μl mesh), drying it at 140 °C for 4 hours, and dissolving the dried activator and carbon-containing compound in the following proportions (% by mass): Carbon-containing compound 0.5-2
．． 5. The activator should be added in an amount of 0.2-5.0. The mixture used is carefully mixed with the activator and the carbon-containing material.Then, the freshly prepared and dried powder mixture is added in a proportion of 10% of the initial weight of the mixture;
Then carefully mix again. Note that powder mixtures can be used as required. The mixture should be
It can be played up to 5 times.

The method proposed herein is based on a dense non-porous diffusion carbide coating with a thickness of 21.0-40.01 and a thickness of 21.5-27.
Microhardness of 0GPa, average height of carbide crystals of 4.2-5.4px, substrate hardness of 4.2-7.4GPa, 4.2
- Minimum hardness in the lower zone of 7.4 GPa, no decarburized zone below the carbide coating and 12,515,6
A coating is produced having a relative wear rate in sliding friction of g/z''s.

The carbide coating has an attractive silver-gray surface and its surface roughness Ra is less than 0.32 ui. Therefore, once the process is completed, the product does not require any finishing treatment or subsequent machining; the coating is evenly spread over the entire surface of the product, including the internal spaces, and effectively adheres to the material of the product. are doing.

The process does not require the use of vacuum equipment, nor does it use gases (hydrogen and argon) that require the provision of special fire and explosion protection equipment.

The process does not involve any substantial hazards to handling personnel or the environment.

Although the process can be repeated up to 7 times, its total duration is less than 20 minutes due to the short duration of its individual stages.
- Not to exceed 22 hours.

The invention will be further elucidated by an example embodiment of a method for depositing a carbide diffusion coating on an iron-carbon alloy article.

Example 1 Chromium powder 195° (65%) is placed in a stainless steel container with inner diameter Sozm, height 1101 shoulders, and wall thickness 5xz.
, diphenyl CI2Cl2H1o3%), ammonium chloride NH,C11,5y (0,5%) and aluminum oxide A1. 300 g of a powder mixture containing Ozl O0,5y (33.5%) were charged. These ingredients had previously been milled, sieved to yield a particle size fraction below 50u++, weighed out according to the formulation and mixed in a mixer.

Next, a carbon and alloy steel test piece with a diameter of 15zi+ and a height of 5u was placed with a distance of 2011 m between the container bottom and the test piece, a distance of 10% m between the container side wall and the test piece, and a distance of 151 m between the test pieces.
1 and immersed into the mixture leaving a distance of 30zz between the test piece and the first cover of the container.

The test pieces were arranged in the − row. Once the test specimens are in the powder mixture, the container is closed with a first stainless steel cover and a 3Qxz thick layer of silica sand is placed on top of the cover.
The second stainless steel cover of the vessel was then closed, a 10 shoulder thick layer of boron oxide was poured on top of the cover, and the vessel was moved into a resistance furnace. Heat the container to 650°C, and at this temperature 1.
Carburizing was performed for 0 hours. The surface of the specimen was saturated with carbon. The carburized specimen was then heated to the diffusion saturation temperature (1000° C.) at a rate of 1.5°/s.

Once a temperature of 1000° C. was achieved, this temperature was maintained for 1.5 hours due to diffusion saturation of the specimen surface by chromium. Once diffusion saturation with chromium was completed, the specimen was cooled to 400°C at a rate of 1.8°/s.
Heating to carburizing temperature, original carburizing
The above operations such as ion proper), heating to diffusion saturation point, diffusion saturation and cooling were repeated once more, after which the container containing the specimen was cooled to ambient temperature in air.

The container was then opened, the powder-saturated mixture was directed for regeneration, and the specimens were tested by conventional methods to determine the physico-mechanical and physico-chemical properties of the resulting carbide-chromium coating.

Test results: The carbide coating is dense, i.e. practically pore-free; - Thickness of the carbide coating, 21.011z; - Microhardness of the carbide coating, 21.6 GPa; - Average height of the carbide crystals;
5.2 μl; - Hardness of the base material, 5.6 GPa; Minimum hardness of one lower zone, 5.6 GPa; - Relative wear rate,
12, 5y/z”s.

Example 2 A diffusion carbide coating was prepared in the vessel described in Example 1.

195g titanium powder (65%) in a container, anthracene CI
4 H+. 3g (1%), ammonyl bromide ANH4B
rl-5y (0,5%) and magnesium oxide 10
300 g of a mixture containing 0.5 g <33.5%) were charged. A powder mixture was prepared as in Example 1. The specimens were used as in Example 1 and placed in a container. The container containing the powder mixture and specimen was placed in a resistance furnace and heated to 560°C. At this temperature, the specimens were carburized for 1.2 hours, resulting in carburization of their surfaces.

The carburized specimens were heated to 950° C. at a rate of 2.4°/s. This temperature is the temperature at which the surface of the product becomes diffusion saturated with titanium. Diffusion saturation lasted for 1.8 hours. Once the diffusion saturation with titanium is completed, the specimen is moved at 1.2°/s.
1. Cooled to 500°C at a rate of
The above operations such as nproper) and cooling were repeated three more times.The container was then opened, the saturating powder mixture was directed for regeneration, and the specimen was exposed to the physical properties of the deposited titanium-carbide coating. Tested using conventional methods for measuring mechanical and physicochemical properties.

Test results: The carbide coating was dense, i.e. virtually pore-free; the thickness of the carbide coating, 28.8 uz; - the microhardness of the carbide coating, 26.8 GPa; - the average height of the carbide crystals; 4.7 μl; - hardness of base material, 4.2 GP
a Minimum hardness in the lower knee zone, 4.2 GPa; - relative wear rate, 18,2y/z''s.

Example 3 A diffusion carbide coating was prepared in the vessel described in Example 1. In a container, 195g (65%) silicon powder, naphthalene C3
゜Ha3FI (1%), ammonium iodide NH4I
1.5y (0.5%) and aluminum oxide A1.0
Powder mixture 300 containing 3100.5g (33,5%)
g was charged. A powder mixture was prepared as in Example 1. The test specimens were used and placed in a container just as in Example 1. The container containing the powder mixture and the specimen immersed therein is then placed in a resistance furnace;
It was heated to 720°C. At this temperature, the test piece was
．． The test pieces were carburized for 6 hours to ensure that their surfaces were carburized.Then, the carburized test pieces were heated at 0.8°/s.
The mixture was heated to 1100°C at a rate of . This temperature is the temperature at which diffusion is saturated by silicon on the surface of the test piece. Diffusion saturation is 1
．． It lasted for 2 hours. Once diffusion saturation with silicon was completed, the specimen was cooled to 300° C. at a rate of 2.4°/s. The above operations of grazing, heating to carburizing temperature, original carburizing, heating to the stage of diffusion saturation, original diffusion saturation and cooling were repeated seven more times.Then, the container was opened and the powder mixture was regenerated. The specimens were then tested to determine the physico-mechanical and physico-chemical properties of the deposited silicon carbide coating.

Test results The carbide coating was dense, i.e. virtually pore-free; the thickness of the carbide coating, 39.8 μl; - the microhardness of the carbide coating, 22°3 GPa; - the average height of the carbide crystals, 4.3ux; - Hardness of base material, 7.4G
Pa; Minimum hardness of one lower zone, 7.4 GPa; - relative wear rate,
20.9g/Is.

Example 4 A diffusion carbide coating was deposited in the container described in Example 1. Container contains chromium powder 195g (65%), polyvinyl chloride 3g (1%), ammonium fluoride NH4F1.5
y (0,5%) and magnesium chloride MyO100,
300 g of a powder mixture containing 5 g (33.5%) were charged. A powder mixture was prepared as in Example 1.

The specimens were also used and placed in a container as in Example 1.

The container containing the powder mixture and specimen was placed in a resistance furnace and heated to 600°C. At this temperature, the specimen was allowed to carburize for 1.1 hours, and the carburized specimen was heated to 1000° C. at a rate of 2.1°/s. At this temperature, the surface of the specimen was diffusion saturated with chromium. Diffusion saturation was performed for 1.7 hours. Once diffusion saturation with chromium was completed, the specimen was cooled to 450°C at a rate of 2.1°/s, then heated to the carburizing temperature,
The above operations of original carburization, heating to the stage of diffusion saturation, original diffusion saturation, and cooling were repeated four times.
The container was then opened, the saturating powder mixture was directed for regeneration, and the specimens were tested to determine the physico-mechanical and physico-chemical properties of the deposited chromium carbide coating.

Test results The carbide coating was dense, i.e. virtually pore-free; the thickness of the carbide coating, 23.7 l; - the microhardness of the carbide coating, 22.0 GPa; - the average height of the carbide crystals. - Hardness of base material, 5.6 GP
a; Minimum hardness of one lower zone, 5.6 GPa; - relative wear rate,
15, 6g/n's.

Example 5 This example uses a regenerated powder mixture of composition according to Example 1 and utilized in accordance with Example 1.

Once the process was completed, the powder mixture was regenerated. For this, the powder mixture is ground in a show crusher and 5
It was sieved through a vibrating sieve with a mesh size not exceeding 50 μl in order to obtain a powder portion with a particle size not below 0.0111. Once the mixture was sieved, it was dried at 140° C. for 4 hours. Then, 266.5y (8
8,8%) with the following components: diphenyl Cl2H163-31F (1,1%
), 1.65 g (10%) ammonium chloride, first dried at 140° C. for 4 hours, 19.5 fI dry chromium powder (
6,5%) and 9.05 g dry aluminum oxide (3
%) was then mixed carefully and the prepared powder mixture was placed in the container according to Example 1.The test piece according to Example 1 was placed in the container containing the powder mixture. The container was then placed in a resistance furnace. 630 containers
The specimens were carburized at this temperature for 0.9 hours. A test piece whose surface was saturated with carbon and then carburized was heated to 1020°C at a rate of 1.5°/s. This temperature is the temperature at which the surface of the specimen undergoes diffusion saturation with chromium. The process of diffusion saturation with chromium is
The test piece was then heated to 2.2°
It was cooled to 350° C. at a rate of /s. ! & After that, the above operations of heating to carburizing temperature, carburizing, heating to diffusion saturation stage, original diffusion saturation, and cooling were repeated once more.

The container was then opened, the saturating powder mixture was directed for regeneration, and the specimens were tested for physico-mechanical and physico-chemical properties of the deposited chromium-carbide coating.

Test results: The carbide coating was dense, i.e. virtually pore-free; - Thickness of the carbide coating, 20.9 ν; - Microhardness of the carbide coating, 22° 5 GPa; - Average height of the carbide crystals. , 5.1uz Knee base material hardness, 4.2G
Pa; Minimum hardness of one lower zone, 4.2 GPa; - relative wear rate,
14. 1! ? /i”s.

The example shows the deposition of a diffusion carbide coating carried out according to previously known methods.

As in Example 1, a powder mixture was prepared and charged into a container, and a test specimen was placed into the container.

The container containing the powder mixture and specimen was placed in a resistance furnace and heated to 800°C. At this temperature, the specimens were carburized for 3.5 hours, allowing their surfaces to become carburized. Once the carburization period was completed, the specimens were heated to the temperature of diffusion saturation, i.e. 1050°C. At this temperature, the surface was diffusion saturated for 3.5 hours.The container was then removed from the oven and allowed to cool to room temperature.

After cooling, the container was opened, the powder mixture was sent for regeneration, and the specimens were tested to determine the physico-mechanical and physico-chemical properties of the deposited chromium carbide coating.

Test results: The carbide coating is dense, i.e. does not have practically any pores; - Thickness of the carbide coating, 12.3 uy; - Microhardness of the carbide coating, 21.3 GPa; - Average height of the carbide crystals. 7. ], B;-Hardness of base material, 6.4GP
a Minimum hardness in the R (decarburized) zone below the knee, 5.8 GPa
; Depth of the coal zone, 171mm Relative wear rate, 36.4g/Is.

Comparing the physico-mechanical and physico-chemical properties of specimens with diffused carbide coatings deposited by the method proposed here and previously known methods, it is found that the physico-mechanical and physico-chemical properties of the coatings obtained according to the invention are It can be concluded that the mechanical properties are significantly higher than in the case of coatings applied according to previously known methods.

Thus, the wear resistance under abrasive conditions of the diffusion carbide coating produced in accordance with the disclosed invention is 2.8-2.
3.3 times higher. Moreover, products with diffused carbide coatings deposited by the method of the invention do not have any decarburization zone beneath the coating.

EFFECTS OF THE INVENTION Iron-carbon alloy articles having a coating deposited according to the method of the disclosed invention have a high surface hardness of up to 24.0 GPa, and have a high surface hardness of up to 24.0 GPa. It is characterized by a wear resistance at sliding friction that is 1.3-1.5 times higher than in the case of coatings made by known methods and a wear resistance that is 2.8-3.3 times higher than in the case of coatings made by known methods. The coating obtained by the inventive method is 35ux
The coating has a thickness of up to 100 mm and has virtually no pores and no decarburization zone beneath the coating.

The invention makes it possible to use ordinary carbon steel instead of expensive high alloys, especially for the construction of critical components. This saves on hard-to-obtain high alloys. Depending on the usage and usage conditions of the product, the practical lifespan of the product is 2-1.
Extends 0 times.

Claims (2)

[Claims] (1) charging a container with a powder mixture containing solid components such as carbide-forming elements, carbon-containing compounds, activators, and inert fillers, and immersing an iron-carbon alloy product within the mixture; heating the products to the carburizing temperature of their surfaces; causing the surfaces of the products to be carburized at the carburizing temperature;
heating to a temperature of diffusion saturation of the surfaces of those products with carbide-forming elements; and diffusion saturation of the surfaces of the products with carbide-forming elements at a temperature selected within the range of 950 to 1100°C. In the method of applying a diffusion carbide coating to a product, the carburization of the surface of the product ranges from 0.6 to 1.2 at a temperature selected from 560 to 720°C.
Heating of the carburized product to a diffusion saturation temperature selected from within 950 to 1100°C is carried out at a rate of 0.8 to 2.4°/s; Carbide formation The diffusion saturation of the product surface by the elements is 1.2 to 1 at a temperature selected within the range of 950 to 1100°C.
．． carried out for a period of time selected from 8 hours; after diffusion saturation of the product surface, the product is
/s at a rate selected from 300 to 500 °C to a selected temperature; characterized in that the above operations are repeated at least once, starting from heating the product to the carburizing temperature. Iron to be
A method of applying a diffusion carbide coating to carbon alloy products. (2) A method for depositing a diffusion carbide coating on an iron-carbon alloy product according to claim (1), characterized in that said operation is repeated up to seven times.