RU2475365C2 - Method of making special coatings and solid bodies on art articles from metallic and non-metallic materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: method comprises cold gas-dynamic spraying of special coating and sold bodies, making gas-powder mix, accelerating mix particles by supersonic gas flow, and transferring them on processed articles. Note here that working gas is heated in intermittent mode. Note also that duration of holding article surface in spraying spot at 50-150°C approximates to or is smaller than that of reaching temperature equilibrium in spraying spot between working gas and processed article material. Note that particle sizes are selected from the range of 50-0.03 mcm. Note here that higher dispersion of particles is used for smaller thickness of coatings.

EFFECT: higher quality of coatings, process efficiency, reduced power consumption.

11 cl, 4 ex

Description

The invention relates to a method for producing special coatings by cold gas-dynamic spraying (hereinafter referred to as CGN) on the surfaces of art products and solid-state forms made of metal — monumental sculpture, elements of the architectural decoration of buildings, bridges and other urban structures exposed to the atmosphere (in the exterior), museum exhibits, objects of arts and crafts (in the interior).

The invention can be used in the processes of restoration, conservation, recreation of cultural heritage objects and can be applied to newly created products of the above nature.

A known method of applying metal-containing coatings on objects made of copper alloys (RU 2201473 C2, 04/27/2003). Powders of copper or copper alloys, as well as zinc, are used as the sprayed material. The spraying is carried out by plasmatrons, gas-flame burners, arc metallizers and detonation-gas guns. As a result, a porous surface forms, the pores of which are additionally impregnated with corrosion inhibitors. The main disadvantages inherent in all methods of thermal spraying are that the process is carried out by molten or close to this state particles, the heating of which is carried out respectively in a plasma, flame, electric arc and detonation-gas flow.

1. When spraying with a plasma method, a high temperature is created in the spraying spot, which causes warping, leads of ancient monuments, made, as a rule, of copper or copper alloys with a high content of impurities;

2. Temperature stresses in the coating, the level of which is comparable, and sometimes even exceeds the adhesive strength, leads to delamination of the coating from the surface of the product.

3. The difficulty of maintaining the necessary spraying conditions, stable arc burning, ensuring a high spraying rate and adhesion.

4. When using electric arc spraying, regardless of the sprayed material used (wire, cord, powder), a rough coating with a high degree of roughness is formed on the surface. The sprayed layer is unstable to shock, mechanical, vibrational loads and torsion.

5. A layer of partially oxidized sprayed particles has a relatively lower protective ability compared to a continuous layer of nitrous or copper oxide.

6. The disadvantages of detonation spraying include low productivity, lack of reliability, a large level of shock loading and acoustic noise; close to 140 dB, which makes it necessary to work in a closed, soundproof box.

7. The use of combustible gases in the flame and detonation spraying method introduces a significant content in the coating of carbon, nitrogen, and other compounds that are contained in the acceptable impurity limits in the initial metal of the sculpture.

8. The impossibility of spraying minerals - basic sulfates and carbonates of copper, corresponding in chemical composition to natural patina, which are subject to destruction in a high-temperature stream.

A known method of sealing a weld by pouring an alloy based on lead, which allows for reliable sealing of the weld without additional mechanical or chemical treatment (RU 2284400 C2, 02.27.2005).

1. The material (metal or alloy) from which the objects are made ("monuments of monumental sculpture and architecture ..."), the seams on which are sealed with the proposed method, is not indicated.

2. The limitation of the method is the temperature of 320-350 ° C of melt pouring, which, with the thickness of the shells (metal) of the overwhelming number of sculptures not exceeding 1-3 mm, can lead to overheating of thin-walled soldered shells of sculptures, a change in the structure of its material and warpage, t. e. to change the plastics of the author’s surface.

3. The use of molding material with a sprue system complicates the process of sealing joints, while when using gas-dynamic spraying, it is sufficient to ensure that the crack is closed with sheet (or another assortment) material from the same lead alloy (instead of backfilling foreign dry non-combustible materials) with its subsequent embossing crack and final spraying with powder material from the corresponding lead alloy.

4. When lead is filled with cracks according to the specified method, as well as when the lead melt is rubbed on monumental sculptures made of copper, for example, copper-punctured sculptures of St. Isaac's Cathedral, air bubbles, cavities and pores are formed due to gas formation during the interaction of the melt and flux.

A known method of restoration of sculptural monumental works of stainless steel sheet by spraying on the surface of the sculpture material from the group of titanium, titanium-palladium, titanium-aluminum, titanium-vanadium (RU 2209138 C1, 07.27.2003).

The disadvantages of this method are:

1. The need for dismantling the sculpture for restoration work, which is unacceptable for works under state protection.

2. The use of magnetron sputtering, which is carried out in chamber-type installations, the working volume of which is very small even for elements of a monumental sculpture and is a limitation during its restoration.

3. Additional heating of the surface of the sculpture element to 400-500 ° C when applied by magnetron or plasma spraying in a vacuum limits the obtaining of a given surface for elements having a thickness of 1-3 mm, since thermal deformation and the subsequent change in the author’s plasticity of the element will inevitably occur. Restoring the original plastic in the future is almost impossible.

4. Coatings from the group titanium, titanium-palladium, titanium-aluminum, titanium-vanadium are possible only for sculptures made of stainless steel, cannot be applied to sculptures made of copper and copper alloys, zinc, cast iron, since in the case of historical non-ferrous metal sculptures, the use of these materials is foreign and unacceptable in general, but the use of cast iron sculptures (other art forms) is unacceptable, since the equipment used in the process of use causes a significant overheating of the cheekbone shell ATGM, which can lead to cracking.

Known solder for brazing zinc and its alloys (RU 2138378 C1, 09.27.1999).

The disadvantages of solder are:

1. The high content of tin in the alloy, not less than 66.8%, which does not correspond to the traditionally used in the creation and restoration of historical monuments made of metal - tertiary (alloy of two-thirds of lead and one-third of tin), which provides the greatest strength of all other permitted for use in the restoration of tin-lead alloys.

2. The indium content in the alloy is up to 1.2%, bismuth up to 0.5%, lithium up to 0.3%, which are foreign impurities in the composition of tin-lead alloys, traditionally used in the creation and restoration of historical monuments made of metal.

3. The temperature of soldering with such an alloy will be not less than 150-250 ° С, which exceeds the temperature in the spot of spraying by a gas-dynamic method with a tin-lead alloy, for example POS-30, POS-40.

Known connecting seam in parts of zinc and its alloys and the method of its production (RU 2146190 C1, 03/10/2000).

The disadvantages of this seam are:

1. The use of a base and filler metals as a heating source to obtain a welded-soldered seam of a gas jet (argon or air) heated to a temperature of 650-750 ° C, above the melting temperature of the base metal, which may adversely affect the shell structure of a historical highly artistic work .

2. In a purely brazed joint made using a tin-zinc eutectic alloy as a solder, the tensile strength is 22-25 MPa, which may not be sufficient to ensure a strong joint.

Closest to the proposed invention is the spraying method according to patent No. 2203347 (RU 2203347 C2, 03/27/2003.)

The main disadvantages of this method are:

1. High temperature in the plasma stream (6000 ° C) and in the spraying spot (at least 500 ° C), which causes negative processes associated with warping, leashes, changes in the metal structure of antiquities, made, as a rule, of copper or copper alloys with a high content of impurities; evaporation and burning out of highly dispersed fractions of particles less than 10 microns.

2. Temperature stresses in the coating, the level of which is comparable with the adhesive strength and leads to its delamination from the surface of the product.

3. Intensive high-temperature electroerosive wear of the plasma torch electrodes makes it difficult to maintain the necessary spraying conditions, stable arc burning, ensure the quality of spraying and adhesion, and the use of air with a high oxygen content as a working gas significantly enhances these processes, reducing the life of the plasma torch to 10 hours and causing active oxidation of metal-containing particles in the stream, especially in a turbulent stream outside the plasma torch.

4. Intense gas evolution from the surface of the sprayed product with the formation of through pores in the coating during plasma spraying, which requires additional processing to protect the product from corrosion.

The proposed invention solves the problem of significantly reducing the temperature and power effects on protected works of cultural heritage, improving the quality of coatings and, in particular, adhesive-cohesive strength, process productivity, increasing efficiency by expanding its functionality and reducing the energy consumption of the CGN method.

The essence of the invention is the use of an improved method of CGN in conservation and restoration work on cultural heritage sites or in the manufacture and decoration of newly created products, mainly on monumental sculptures made of metal, mainly from copper and copper alloys (bronze, tombac, brass) and zinc alloys (spy).

To achieve the named technical result in the proposed method of coating, including the formation of a gas-powder mixture, acceleration of the particles of the mixture with a supersonic heated gas stream and transferring them to the workpiece (product), it is new that the working gas is heated in a batch mode, while the duration of the period exposure of the product surface in the spray spot at a temperature of T = 50-150 ° C is close to or less than the time to establish temperature equilibrium in the spray spot between the working gas the material of the workpiece, and a particle size selected from the group 50-0,03 micron, while for small coating thickness using a high dispersion of the particles.

Copper or lead plated with copper is used as a coating material in the restoration, manufacture, and decoration of newly created copper products (sculptures).

Zinc powders, or a mixture of zinc with tin and lead, or lead plated with zinc, are used as the coating material for the sculptures made from the spyatre, as well as the shells of the sculptures and their elements connected by tin-lead solder.

As a coating material for the surface of bronze sculptures made using the “lost wax” casting technique, surface sections of tin-lead solders on a bronze sculpture, bronze powders and non-ferrous metal powders plated with bronze are used.

As a coating material for the surface of brass and tompak (half-pack) products, surface areas of tin-lead solders on products from copper-zinc alloys, powders of brass, copper, copper-zinc powder mixture or non-ferrous metal powders plated with brass are used.

In all the above cases, the coating thickness is provided in the range of 40-100 microns.

When filling through holes in the sculpture shell, after inserting pre-prepared tertiary plates (or sculpture shell material) and closing the through hole, spraying along the hole boundary with tertiary powder or material corresponding to the sculpture shell, and then the recess is sprayed “flush” with the shell surface by material powder corresponding to the shell material of the sculpture.

When sealing non-through defects in the shell of the sculpture, the depressions are filled by spraying a tertiary powder or a material similar in composition to the material of the shell of the sculpture.

When forming an artificial decorative protective coating (patina) according to the "natural mechanism" (Kalish MK. Natural protective films on copper alloys. M .: Metallurgy, 1971. 200 pp.), On the surface of sculptures made of copper and copper alloys consistently spray the components of the patina:

- cuprite, 5-20 microns thick;

- tenorite, 3-10 microns thick;

- basic copper sulfate (brocantite, antlerite, etc.), or basic copper carbonate (malachite, azurite, etc.), or basic copper chloride (atacamite, nantokite, botallakite) with a thickness of 15-25 microns with an initial powder size of not more than 30 microns. Thus, a much more thorough protection of the metal surface of sculptures made of copper and copper alloys is made in comparison with traditionally used chemical methods (Bondarenko S.M., Degtyarev M.A., Kuznetsov S.V. Modern technologies for creating patina on metal works of art . Magazine "Relic. Restoration, Preservation, Museums. St. Petersburg, No. 22/2010, p.24-27).

Coating with non-ferrous metal powders and their alloys is carried out both on the entire restored surface, and on loss sites, directly on monuments without disassembling structures and their elements, while the coating thickness of expensive fine powders can be 5-10 microns with disposal and subsequent use particles not fixed on the surface.

Surface coating of natural stone - granite, quartzite, malachite, etc. in the form of drawings, bas-reliefs, inscriptions, etc. it is produced through a stencil or without it, in layers, with the first layer applied metal with increased adhesion to the stone mixed with powder similar in composition to the material of the stone, with a content of not more than 20 vol.% and a particle size of not more than 15 microns, and it is coated with a powder of decorative metal, alloy, or a mixture thereof, or ceramic powder clad with metal or alloy.

Examples of the implementation of the method of obtaining a functional surface by gas-dynamic spraying, which were first introduced into the scientific and restoration circulation in St. Petersburg on world cultural heritage sites - the work was carried out according to methods agreed upon with the Committee for State Control, Use and Protection of Historical and Cultural Monuments (KGIOP).

Example 1

In five sculptures of angels of St. Isaac's Cathedral, located under the attics, made in the technique of punctured sculpture of copper, using areas covered with a tertiary and copper-plated galvanoplastic method, restoration work was carried out in 2002-2003.

The surface areas of the tertiary sculpture, which over time lost the galvanoplastic copper layer, were first repaired in places with caverns, cracks, through holes in a gas-dynamic manner, by spraying a mixture of tin and lead powders in a stoichiometric ratio, providing a composition corresponding to the composition in the sprayed coating tertiary. The size of the powders is less than 40 microns. When sealing through holes, tertiary plates were used that were inserted into the hole, straightened, closing the hole and forming a recess, and then sprayed in a gas-dynamic manner. During operation, the plates were held by a pre-inserted tertiary rod, which, after dusting the plate, bit off along the perimeter of the hole. After smoothing the patched defects in accordance with the sculpture plastic at the restoration site, the tertiary surface was also copper-plated by gas dynamic spraying with copper particles of less than 40 microns. The copper surface of the sculpture, which had the same defects (cavities, indentations, etc.), was restored in the same way, sometimes copper powder was used instead of the tertiary.

Example 2

In 2002, the copper cladding of the weather vane was restored in the form of a figure of a flying angel with a cross crowning the spire of the Peter and Paul Cathedral. The restoration consisted of coppering the main skin for subsequent gilding, from which a thin copper foil peeled off, on which the author's relief was carved (the finest drawing of the plumage of the wings), as well as the sealing of cracks and holes in the skin of the weather vane and cross. Replenishment of the lost foil was carried out by spraying a copper powder material with a fraction of less than 40 microns. At the same time, at the boundary of the lost and existing foil during the deposition process, areas of non-adherence of the existing foil were revealed, which peeled off under the action of a two-phase flow of fine particles and air. Thus, defective areas of minted copper were found and removed.

Cracks and gaps were repaired by spraying a mixture of tin and lead powders in a stoichiometric ratio, providing a composition corresponding to the tertiary composition in the sprayed coating. Initially, at the place of the defect on the reverse side, the hole was closed with a tertiary plate, dusted with a tertiary mixture to the structure shell, which ensured reliable fastening of the plate to the shell and seal of the hole. Then, from the author's side, the resulting depression was sealed with a powder tertiary mixture or copper. Small cracks were repaired by spraying copper. The size of the powders is less than 40 microns. After spraying and smoothing the sprayed surface in accordance with the plastic, the surface was additionally sprayed with a thin (40-60 μm) layer of copper and minted in accordance with the author's intention.

Example 3

In May 2005, on the occasion of the 100th anniversary of the State Duma, restoration of the 19th century spy-chandelier of the Catherine (White-Column) Hall of the Tauride Palace was carried out for subsequent gilding.

The finely dispersed lead powder by the CGN method was applied to the surface of lead punctured rims on chandeliers, which over time and under the influence of corrosion turned into perforated foil.

Also, on chandelier elements made of a spider, the losses were compensated by the CGN method by spraying a mixture of powders of zinc, tin and lead in a stoichiometric ratio, which ensures that the composition corresponding to the composition of the spider is obtained in the sprayed coating.

Example 4

In the period from autumn 2010 to spring 2011, restoration work is being carried out in accordance with the techniques approved by the Committee for State Control, Use and Protection of Monuments of History and Culture (KGIOP) and the Customer (St. Isaac's Cathedral) on the sculpture “Apostle Paul”, located on the northern portico , and the sculptural group "Angels with a Lamp" on the southwestern attic of St. Isaac's Cathedral. For restoration, the CGN method described in Example 1 is used, as well as patination according to the method proposed in this Application instead of the traditionally applied chemical patination (Degtyarev M.A. Types of coatings and the technical requirements for them when restoring monumental bronze and copper sculptures // " Sculpture of the XVIII-XIX centuries in the open air. Problems of conservation and exhibiting "State Museum of Urban Sculpture, St. Petersburg, 2010, pp. 78-81).

Claims (11)

1. The method of obtaining by cold gas-dynamic spraying of special coatings and solid-state forms on art products from metal and non-metallic materials, including the formation of a gas-powder mixture, acceleration of the mixture particles by a supersonic heated gas stream and transferring them to the workpiece, characterized in that the working gas is heated in a batch mode, while the duration of the exposure period of the product surface in the spraying spot at a temperature of T = 50-150 ° C is close or less than the time set Lenia temperature equilibrium in place between the deposition process gas and the material of the workpiece, and a particle size selected from the group 50-0,03 micron, while for small coating thickness using a high dispersion of the particles. 2. The method according to claim 1, characterized in that as the coating material in the restoration, manufacture and decoration of newly created copper products (sculptures), copper or lead powders clad with copper are used. 3. The method according to claim 1, characterized in that, as the coating material of the sculptures made of a spider, as well as shells of sculptures and their elements connected by tin-lead solder, zinc powders or a mixture of zinc with tin and lead or lead (tin are used lead solder), zinc plated. 4. The method according to claim 1, characterized in that the bronze powders and non-ferrous metal powders plated with bronze are used as the coating material for the surface of bronze sculptures made using the "lost wax casting" casting technique, surface sections of tin-lead solders on a bronze sculpture . 5. The method according to claim 1, characterized in that as the coating material of the surface of brass and tompak (half-pack) products, surface areas of tin-lead solders on products from copper-zinc alloys, use powders of brass, copper, copper-zinc powder mixture , or powders of non-ferrous metals plated with brass. 6. The method according to any one of claims 2 to 5, characterized in that the coating thickness is provided in the range of 40-100 microns. 7. The method according to any one of claims 1 to 5, characterized in that when sealing through holes in the shell of the sculpture, after inserting pre-prepared tertiary plates (or material of the shell of the sculpture) and closing the through hole, spraying along the border of the hole with tertiary powder or material close to the composition of the shell of the sculpture and then the recess is sprayed “flush” with the surface of the shell with a powder material corresponding to the material of the shell of the sculpture. 8. The method according to any one of claims 1 to 5, characterized in that when filling non-through defects in the sculpture shell, the cavities are filled by spraying a tertiary powder or material similar in composition to the sculpture shell material. 9. The method according to claim 1, characterized in that when forming an artificial decorative protective coating (patina), the components of the patina are sequentially sprayed on the surface of the sculptures made of copper and copper alloys:
- cuprite, 5-20 microns thick;
- tenorite, 3-10 microns thick;
- basic copper sulfate (brocantite, antlerite, etc.) or basic copper carbonate (malachite, azurite, etc.) or basic copper chloride (atacamite, nantokite, botallakite), 15-25 microns thick with an initial powder size of not more than 30 microns. 10. The method according to claim 1, characterized in that the coating with powders of non-ferrous metals and their alloys is carried out both on the entire restored surface and on the areas of loss, directly on the monuments without disassembling the structures and their elements, while the coating thickness is made of expensive highly dispersed powders can be 5-10 microns with disposal and subsequent use of particles not fixed on the surface. 11. The method according to claim 1, characterized in that the coating on the surface of natural stone - granite, quartzite, malachite, etc. in the form of drawings, bas-reliefs, inscriptions, etc. it is produced through a stencil or without it, in layers, with the first layer applied metal with increased adhesion to the stone mixed with powder similar in composition to the material of the stone, with a content of not more than 20 vol.% and a particle size of not more than 15 microns, and it is coated with a powder of decorative metal, an alloy or a mixture thereof, or a ceramic powder clad with a metal alloy.