RU2354743C2 - Application method of thin-film coating on metal works - Google Patents

Abstract

FIELD: processes.

SUBSTANCE: invention can be used with manufacturing of cutting tools, products of triboengineering function, heavy loaded machinery and mechanisms. Coating is applied by means of displacement of low-temperature plasma stream, containing carbon, silicon, hydrogen, nitrogen, oxygen and argon, lengthwise the product surface. Products are preheated up to the temperature 50-100°C. Displacement of low-temperature plasma stream is implemented at a rate of 3-150 mm/s. Total time of coating is assigned depending on processing surface area and coating thickness.

EFFECT: ensured by coating of thin-film wear-resistant coating with defined thickness with high adhesion to the basis it is achieved useful increase of product's service durability by increased reproducibility.

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Description

The invention relates to methods for increasing the durability and performance of various metal products - cutting tools, tooling parts (for cold and hot pressure machining, foundry tooling, measuring tools), tribological products (rolling bearings, gears), highly loaded machine parts and mechanisms, etc due to the application of a thin-film wear-resistant coating on their working surfaces and can be used in all industries.

Improving the efficiency and service life of various metal products largely depends on the physical and mechanical properties of the surface, including hardness, residual stresses, and roughness parameters. The known technology of plasma plasma hardening, in which a thin-film hardening silicon-carbon-containing coating is applied to the surface of the products [Sosnin N.A., Topolyansky P.A., Vichik B.L. Plasma coatings (technology and equipment). - St. Petersburg: Publishing House of the "Knowledge" of Russia, 1992. - 28 p.]. However, there is no information about the optimal parameters of the plasma jet, the modes and conditions of stable application of high-quality thin-film hardening coating, which allows to increase the operational stability of the products.

In recent years, this technology has been significantly improved. It was found that for applying a thin-film hardening coating with high adhesive properties, it is possible to reduce the thermal effect of the plasma jet on the metal surface of the processed products. At the same time, the possibility of a significant increase in the performance and operational stability of products with a minimum thickness of less than 2 microns was shown.

The known technology of chemical-thermal processing of products from hard alloy [ed. certificate No. 1793004, MKI C23C 8/36, B22F 3/24, published 1993.02.07], in which the heating is carried out by a jet of low-temperature argon plasma of the following composition, wt.%: nitrogen 0.09-0.15; carbon 0.09-0.15; silicon 0.16-0.30; hydrogen 0.04-3.00; argon is the rest, and the jet is moved along the surface of the product at a speed of 4-5 mm / s.

The disadvantage of this method is the low reproducibility of the effect of increasing the operational stability due to different thicknesses of the hardened layer of the metal surface, associated with unregulated modes of saturation of the surface with alloying elements and uncontrolled heating of the products by a plasma jet during processing.

The closest analogue of the invention is a method of chemical-thermal processing of products from hard alloy and steel [RF patent No. 2231573, MKI C23C 8/38, publ. 2004.02.20], in which heating is carried out by a jet of low-temperature argon plasma containing carbon, silicon, hydrogen and argon, which is moved along the surface of the product, characterized in that low-temperature argon plasma of the following composition is used, wt.%: Carbon 0.06-0 ,twenty; hydrogen 0.04-3.50; silicon 0.16-0.80; nitrogen or oxygen 0.01-0.07; argon is the rest, and the jet is moved at a speed of 1-15 mm / s.

To implement the method according to the patent of the Russian Federation No. 2231573, a modernized arc plasma torch of the UPNS-304M installation of domestic production with an additional unit of a liquid feeder is used. An organosilicon polymer such as polyorganosiloxane (polyorganosilazane) is used as a working reagent of a liquid feeder.

The operational durability of products after such processing increases, but the effect of increasing durability is negligible and unstable. This is due to the fact that the surface treatment time with a plasma jet is not specified, which can lead to the formation of a coating of non-optimal thickness, its possible imperfection and unevenness in thickness, and also creates conditions for softening the surface layers of hardened steels. The latter is also facilitated by the relatively low velocity of the plasma jet along the surface of the product. All this does not allow not only to obtain a stable increase in the operational stability of the processed products, but for a number of products it generally excludes the use of this technology, for example, for clearance-free dies (due to the uncertain thickness of the applied coating).

The problem to which the invention is directed, is a significant and stable increase in the operational stability of various product ranges due to the application of thin-film coatings of optimal thickness.

The problem is solved in that in the method of applying a thin film coating to metal products, including the processing of a jet of low-temperature argon plasma containing carbon, hydrogen, silicon, nitrogen, oxygen and argon, and the jet is moved along the surface of the product, the zone of the upcoming treatment is preheated to a temperature of 50 -100 ° C, the jet is moved at a speed of 3-150 mm / s, and the total coating time is assigned from the ratio

t = K s s f

where t is the total coating time in seconds (excluding the time of intermediate cooling of the product); K is a coefficient equal to 0.25 ... 0.5; s is the surface area to be treated in mm ² ; f is the specified coating thickness in micrometers.

The implementation of the technological solution is carried out using a specialized installation UFPU-111 of domestic production, which includes: a current source; plasmatron PS-3-01; Plasma-chemical generator NPH-3-01; a unit of equipment (containing a liquid feeder with hardening reagents, an arc ignition device, electrical, gas and water communications and controls). As a reagent for coating, a two-component technological preparation CETOL is used, which contains an organosilicon polymer such as polyorganosiloxane (polyorganosilazane).

Preheating the surface of the product to a temperature of 50-100 ° C creates the conditions for the formation in the air atmosphere on the surface of steels and alloys of a thin and dense oxide film with a thickness of the order of 0.025-0.030 microns. An oxide film of optimal thickness formed on the metal surface as a result of preheating to a temperature of 50-100 ° C significantly increases the adhesive strength of adhesion to the applied thin-film coating by increasing the development and imperfection of the base surface and chemical interaction with the coating material. Higher temperatures (above 100 ° C) contribute to the formation on the metal surface of a thicker and more friable oxide film, which does not give the necessary effect of increasing the adhesion strength of the coating to the substrate. An additional important result of preheating is the dehydration of the product surface (evaporation of water condensate), which also contributes to an increase in the adhesion of the applied coating.

Increasing the durability of various products is directly related to the thickness of the wear-resistant coating applied. A coating with a thickness of more than 3 μm worsens the surface roughness parameters compared to the initial roughness, has a low thermal conductivity compared to the metal base, and also an increased tendency to microcrack formation. Field tests have shown that in most cases, coating even a minimum thickness of the order of 0.5 microns or less provides a significant increase in the operational durability of the products (by hundreds of%). This is due to the fact that, due to its high hardness, chemical inertness, low friction coefficient and significant electrical resistance (10 ⁶ Ohm · m), the coating forms a film barrier that prevents the setting of contact surfaces. In addition, the coating has sufficient corrosion resistance and heat resistance (up to 1000 ° C). The ability to coat a minimum thickness expands the range of hardenable products, including backlash-free dies, high-precision tools, calibers, etc., and the implementation of the process itself allows to increase the productivity of coating.

In some cases, for example, when coating the working surfaces of injection molds, it is necessary to have an increased coating thickness (up to 2 μm). The choice of parameters for the application of such a coating can be obtained by calculating the above ratio.

When assigning the total coating time from the relation t = K · s · f, the actual coating thickness f _p with respect to a given thickness f has the maximum possible difference in absolute value | (f _p -f) · 100% / f | no more than 50%, which, as operational tests have shown, is perfectly acceptable.

Studies have established that the cooling rate of the coating is about (10 ¹⁰ ... 10 ¹² ) K / s. At these cooling rates, the coating hardens in an amorphous state. The microhardness of the obtained thin-film coating, correctly measured at a load on the indenter of 0.5 g, has a value of about 52 GPa, which is significantly higher than with technologies different from the proposed method.

An important condition for applying a high-quality thin-film coating is the movement of the plasma torch at speeds greater than 3 mm / s with the provision of a multi-cycle process of applying a hardening coating (usually with intermediate cooling of the product). When cyclically applying a thin-film coating for the same total processing time, a greater microhardness of the coating-substrate composition is observed for a shorter unit cycle time, which reduces the heating of the substrate, which corresponds to increased speeds of the plasma jet from 3 to 150 mm / s. Exceeding the upper velocity limit leads to negative gas-dynamic processes of interaction between the plasma jet and the surface being treated.

The invention is illustrated by the following examples.

Example 1. Matrices and punches of a die cut stamp 1709.5110-P30 made of X12M steel were treated with a jet of low-temperature argon plasma containing carbon, silicon, hydrogen, nitrogen, oxygen, and argon under the conditions and parameters of the thin-film hardening coating deposition conditions specified in the present invention. This technological solution was implemented using the UFPU-111 installation of domestic production. Pre-heating of the stamp parts was carried out in an oven to temperatures of 50, 75 and 100 ° C. Process operating parameters: arc current - 100 A, plasma-forming argon flow rate - 1.5-2.0 l / min, transporting argon flow rate - 0.9-1.2 l / min, protective argon flow rate - 1.5-2, 5 l / min; the distance between the plasma-chemical generator and the treated surface is 10-20 mm. The speed of movement of the plasma torch along the treated surface is 3.0; 76.5 and 150 mm / s. The total coating time for a given thickness of 1 μm was 752; 1128 and 1504 s. The processing mode is multi-cycle.

As a reagent for coating, a two-component technological preparation CETOL was used, which contains an organosilicon polymer of the type polyorganosiloxane (polyorganosilazane).

Coating parameters: preheating temperature, total coating time, plasma torch moving speed, corresponded to the lower, middle, and upper levels of values (Table 1).

Tests for the operational resistance of punching dies 1709.5110-P30 from steel X12M were carried out when stamping parts 017DA8-667-437 from galvanized steel 08ps 0.55 mm thick. Operational durability was assessed by the ratio of parts stamped with hardened and unstressed dies by the quality of the stamped parts (no burrs). The results are shown in table 1.

Table 1 Dependence of the service life of dies 1709.5110-P30 on the mode of applying a reinforcing thin-film coating Preheating temperature, ° С Specified coating thickness f, microns Total coating time t, s The speed of the plasma torch, mm / s The resulting coating thickness
f _p , μm The coefficient of increase resistance To _article fifty 1,0 752 3.0 0.5 3,5 75 1,0 1128 76.5 0.9 4.4 one hundred 1,0 1504 150 1.4 3.9

Example 2. Non-gap die cutting dies 2ShB11076 made of X12MF steel were treated with a jet of low-temperature argon plasma containing carbon, silicon, hydrogen, nitrogen, oxygen, and argon under the conditions and parameters of the thin-film hardening coating deposition conditions specified in the present invention. This technological solution was implemented using the UFPU-111 installation of domestic production. Pre-heating of the stamp parts was carried out in an oven to temperatures of 50, 75 and 100 ° C. Process operating parameters: arc current - 100 A, plasma-forming argon flow rate - 1.5-2.0 l / min, transporting argon flow rate - 0.9-1.2 l / min, protective argon flow rate - 1.5-2, 5 l / min; the distance between the plasma-chemical generator and the treated surface is 10-20 mm. The speed of movement of the plasma torch along the treated surface is 3.0; 76.5 and 150 mm / s. The total coating time for a given thickness of 0.5 mm was 408; 612 and 816 s. The processing mode is multi-cycle.

As a reagent for coating, a two-component technological preparation CETOL was used, which contains an organosilicon polymer of the type polyorganosiloxane (polyorganosilazane).

Coating parameters: preheating temperature, total coating time, plasmatron moving speed corresponded to the lower, middle, and upper levels of values (Table 2).

Tests for the operational resistance of die-cutting backlash-free dies 2ShB11076 made of X12MF steel were carried out when stamping parts made of 65G steel with a thickness of 0.8 μm. Operational durability was assessed by the ratio of parts stamped with hardened and unstressed dies by the quality of the stamped parts (no burrs). The results are shown in table.2.

table 2 Dependence of the service life of dies 2ShB11076 on the mode of applying a reinforcing thin-film coating Preheating temperature, ° С Specified coating thickness f, microns Total coating time t, s The speed of the plasma torch, mm / s The resulting coating thickness f _p , microns The coefficient of increase resistance To _article fifty 0.5 408 3.0 0.3 2.9 75 0.5 612 76.5 0.5 3.4 one hundred 0.5 816 150 0.7 3.0

Example 3. Injection molds 147-131 LTNMP-100 made of 4X5MFS steel were treated with a jet of low-temperature argon plasma containing carbon, silicon, hydrogen, nitrogen, oxygen and argon under the conditions and parameters of the thin-film hardening coating deposition conditions specified in the present invention. This technological solution was implemented using the UFPU-111 installation of domestic production. Pre-heating of the stamp parts was carried out in an oven to temperatures of 50, 75 and 100 ° C. Process operating parameters: arc current - 100 A, plasma-forming argon flow rate - 1.5-2.0 l / min, transporting argon flow rate - 0.9-1.2 l / min, protective argon flow rate - 1.5-2, 5 l / min; the distance between the plasma-chemical generator and the treated surface is 10-20 mm. The speed of movement of the plasma torch along the treated surface is 3.0; 76.5 and 150 mm / s. The total coating time for a given thickness of 2 μm was 6280; 9420 and 12560 s. The processing mode is multi-cycle.

As a reagent for coating, a two-component technological preparation CETOL was used, which contains an organosilicon polymer of the type polyorganosiloxane (polyorganosilazane).

Coating parameters: preheating temperature, total coating time, plasmatron moving speed corresponded to the lower, middle, and upper levels of values (Table 3).

Tests for the operational resistance of injection molds 147-131 LTNMP-100 from steel 4X5MFS were carried out during casting of ring 124 from an alloy of brass LTs16K4. Durability was evaluated by the ratio of parts cast in hardened and unstrengthened injection molds before the appearance of a heat grid. The results are shown in table.3.

Table 3 Dependence of the service life of injection molds 147-131 LTNMP-100 on the mode of applying a reinforcing thin-film coating Preheating temperature, ° С Specified coating thickness f, microns Total coating time t, s The speed of the plasma torch, mm / s The resulting coating thickness f _p , microns The coefficient of increase resistance To _article fifty 2.0 6280 3 1.7 13.1 75 2.0 9420 76.5 2,3 15.7 one hundred 2.0 12560 150 3.0 14,4

Example 4. Plates of carbide VK6 were treated with a jet of low-temperature argon plasma containing carbon, silicon, hydrogen, nitrogen, oxygen and argon under the conditions and parameters of the modes of deposition of a thin-film hardening coating specified in the present invention. This technological solution was implemented using the UFPU-111 installation of domestic production. Pre-heating of the stamp parts was carried out in an oven to temperatures of 50, 75 and 100 ° C. Process operating parameters: arc current - 100 A, plasma-forming argon flow rate - 1.5-2.0 l / min, transporting argon flow rate - 0.9-1.2 l / min, protective argon flow rate - 1.5-2, 5 l / min; the distance between the plasma-chemical generator and the treated surface is 10-20 mm. The speed of movement of the plasma torch along the treated surface is 3.0; 76.5 and 150 mm / s. The total coating time for a given thickness of 1.2 μm was 58; 87 and 115 s. The processing mode is multi-cycle.

As a reagent for coating, a two-component technological preparation CETOL was used, which contains an organosilicon polymer of the type polyorganosiloxane (polyorganosilazane).

Coating parameters: preheating temperature, total coating time, plasma torch moving speed, corresponded to the lower, middle, and upper levels of values (Table 4).

Tests for the operational stability of VK6 carbide inserts were carried out when machining parts made of 25L steel. Resistance was evaluated by the ratio of parts machined by hardened and unhardened plates until critical wear of the faces of the plates appeared. The results are shown in table 4.

Table 4 Dependence of operational stability on the mode of applying a reinforcing thin-film coating Preheating temperature, ° С Specified coating thickness f, microns Total coating time t, s The speed of the plasma torch, mm / s The resulting coating thickness f _p , microns The coefficient of increase resistance To _article fifty 1,2 58 3 0.5 3.0 75 1,2 87 76.5 1,1 3.4 one hundred 1,2 115 150 1,6 3.2

The effect of using the proposed method of applying a thin film coating on metal products is achieved by:

a) restrictions on the total time of coating, associated with a certain ratio with the specified thickness of the applied thin-film coating;

b) increasing the adhesion of the applied thin-film coating to the base, due to the preheating of the product in air to a temperature of 50-100 ° C and the formation of a thin and dense oxide film on the surface of the substrate, many times increasing the adhesive strength of adhesion of the coating to the substrate; increased adhesion of the coating to the base during coating helps to create compressive residual stresses in the surface layer of the metal, which increase the operational resistance of articles with a coating even of a minimum thickness of the order of 0.5 microns or less;

c) increased velocity of the plasma jet along the surface of the product, which also eliminates the possibility of softening tempering.

As a result, a thin film coating is formed on the surface to be treated, which has an optimal complex of hardening properties: a coating of even a minimum thickness of 0.5 μm or less provides a significant increase in operational resistance (by hundreds of%), which is determined by the high microhardness of the resulting coating (up to 52 GPa), increased adhesion to the base, chemical inertness, low coefficient of friction, dielectric properties of the coating, which forms a film barrier that prevents the setting of contact surfaces. In addition, this coating has sufficient corrosion resistance and heat resistance (up to 1000 ° C). Under the conditions and parameters of the application regimes of the reinforcing thin-film coating specified in the invention, it is possible to obtain compressive residual stresses in the surface layer of the metal with a thickness of up to 10 μm, which exclude the formation of microcracks during operation and reduce the tendency to fatigue fractures. Compressive stresses arise due to the difference in the thermal expansion coefficients and the temperature of the substrate material and the coating and increased adhesion of the coating due to the formation of strong intermolecular and chemical bonds of the coating with the base, micro-rheological processes associated with filling the roughness cavities, as well as microcracks and micropores of the substrate during coating formation. The conditions and parameters of the application regimes of the hardening thin-film coating specified in the invention provide a significant and stable increase in the operational stability of products with good reproducibility and the expansion of the range of processed products.

Claims (1)

A method of applying a thin film coating to metal products, including moving a jet of low temperature plasma containing carbon, silicon, hydrogen, nitrogen, oxygen and argon, along the surface of the product, characterized in that the products are preheated to a temperature of 50-100 ° C, and the movement of the jet low temperature plasma is carried out at a speed of 3-150 mm / s, while the total coating time is prescribed depending on the area of the treated surface and the coating thickness.