What is Thermal Spray Technology

       Thermal spraying is to use a certain heat source (such as electric arc, plasma spraying or combustion flame, etc.) to heat and melt the coating material (powder or filamentary metal or non-metallic material), and atomize it into extremely fine particles with high-speed airflow. And spray on the surface of the workpiece at a high speed to form a coating.

Thermal spray alloy powders include nickel-based, iron-based and cobalt-based alloy powders, which are used in the repair and protection of mechanical parts according to the hardness of the coating. It can make mechanical parts obtain one or more properties, such as wear resistance, corrosion resistance, oxidation resistance, heat resistance, etc.

Thermal spray technology features:

1. The base material is not limited, it can be metal or non-metal, and can be sprayed on various base materials;

2. The spraying materials are very wide, and the thermal spraying technology can spray almost all solid engineering materials such as cemented carbide, ceramics, metals, graphite, etc.;

3. The temperature of the base material during spraying is very low, and there is no stress or deformation.

4. Flexible and convenient operation process, not limited by the shape of the workpiece, Shigongfangbian;

5. The coating thickness is between 0.01 and several millimeters;

6. The properties of the coating are different, and it can form a coating with various special functions such as wear resistance, corrosion resistance, insulation, oxidation resistance, insulation, conductivity, radiation protection and so on.

7. Strong adaptability and good economic benefits.

Second, the principle of thermal spraying

The so-called thermal spraying is to use a specific heat source such as electric arc, plasma arc, combustion flame, etc. to heat powder or filamentary metal and non-metallic coating materials into a molten or semi-molten state. The technology of forming a surface covering layer with various functions by the force of the flame flow itself or the atomization of additional high-speed air flow and spraying it on the surface of the pretreated base material at a certain speed.

The coating material can be powder, ribbon, wire or rod.

Thermal spray guns provide the necessary heat from gas, electric or plasma arcs. The thermal spray material is heated to a plastic or molten state and then accelerated by compressed air, causing a beam of bound particles to strike the surface of the substrate.

The particles impacting the surface are deformed by punching to form a laminate that adheres to the surface of the prepared substrate, which then cools and accumulates, eventually forming a layered coating.

Due to the different coating materials, it can achieve high temperature corrosion resistance, wear resistance, heat insulation, anti-electromagnetic wave and other functions.

The classification of thermal spraying should be based on the form of heat source. On this basis, it can be re-sprayed in the form of spraying materials (powder, wire, rod material), material properties (metal, non-metal), energy level (high energy, high speed), spraying environment (atmosphere, vacuum, negative pressure). wait.

Thermal spraying can be simply divided into four categories: flame spraying, arc spraying, plasma spraying and special spraying.

3. Thermal spraying equipment and technology

Although the methods of thermal spraying vary, according to the principle of thermal spraying technology, the equipment is mainly composed of spray gun, heat source, coating material supply device, control system and cooling system.

The thermal spraying process is: workpiece surface pretreatment→workpiece preheating→spraying→coating post-treatment

1) Surface pretreatment

In order for the coating to bond well to the substrate material, the substrate surface must be clean and rough, and there are many ways to decontaminate and roughen the surface. The choice of method depends on the design requirements of the coating and factors such as the material, shape, thickness, original surface condition and application conditions of the substrate. The purpose of the decontamination treatment is to remove all dirt on the surface of the workpiece, such as oxidized skin, oil stains, paint and other dirt. The key is to remove the surface of the workpiece and penetrate the grease in it.

2) Preheat

The purpose of preheating is to remove moisture and moisture from the surface of the workpiece and to increase the interface temperature when the spray particles come into contact with the workpiece. In order to improve the bonding strength of the coating and the substrate, reduce the stress caused by the difference between the substrate and the coating material, which leads to the cracking of the coating.

3) Spray

Which spraying method is used for spraying mainly depends on the selection of spraying materials, the working conditions of the workpiece and the requirements for coating quality.

4) Post-coating treatment

The coating obtained by spraying cannot be used directly, and a series of post-treatments must be carried out.

thermal spray applications

Thermal spraying is widely used in various industrial and mechanical industries. Widely used in foundry, paper, textile, printing, steel, metallurgy, electric power, transportation, chemical industry, glass, electrician, municipal, light industry and other industries. The following small series will introduce you in detail:

1. Castings

Casting and forging equipment work in dusty and corrosive environments, and the wear and corrosion of mechanical parts will be very serious. Xuzhou Tiangong Surface Technology can repair the parts of various hydraulic systems in the foundry, such as the repair and transformation of hydraulic plungers, and coordinate with various parts such as bearing positions, sealing positions, chemical and pesticide machinery, etc. It works in an acidic environment, so when repairing such machinery, the anti-corrosion problem of the hydraulic plunger in the new factory of Yipong should be taken into account. Repair of pumps, plungers, spools, etc. in hydraulic and pressure systems. Such as various bearing seats, motor rotors, road rollers, etc. of flour mills; repair of various components of imported sugar-making equipment.

2. Paper machinery

Strengthening and repairing the inner wall of boilers, ovens and ovens; strengthening and repairing various roller surfaces; repairing parts such as centrifugal pumps, axial flow pumps, steam boilers, valves and mixer shaft seals; strengthening the surface of corrugated rollers (after strengthening); corrugated rollers The surface hardness can be increased to hv1200, and the service life of the corrugated roller can reach more than 40 million meters).

3. Textiles

Roller, guide hook, loom weft selection refers to wear-resistant coating; cotton dredging press roller, small roller, tin roller, cast iron outer plate, roller surface, feeder Mianluolazhou, upper knife drive shaft, Adolf shaft; sawtooth yarn machine Through steam valve, side shaft plane combination of roasting chamber; submerged flower basket shaft, upper pulping roller shaft head, main shaft journal, guide roller, pulping roller, moisture measuring roller, journal, cloth yarn journal; gear pull out Machine rollers, large rollers (black rollers), complete machine rollers, four-machine rollers, hot rollers, sub-rollers, guide rollers, embossing rollers and journals, wire wheels, grinding discs (sheets) and other wear-resistant coatings.

4. Printing

Printing press rolls; ceramic mesh rolls; coating rolls, ink rolls, printing rolls, water rolls; tooth pads; toothed sheets, etc.

5. Metallurgy

Heat-resistant and anti-corrosion coatings for blast furnace tuyere and slag mouth; molds, guide rolls, and conveying rolls for slab continuous casting production lines; various process rolls in steel and non-ferrous metal processing; various types of rolls (such as continuous annealing furnace rolls, plating Zinc sinking rollers, various guide rollers, tension rollers of steel surface treatment production lines, etc.) have the characteristics of wear resistance, corrosion resistance and tumor accumulation resistance.

5. Electricity

Ball mill, steam turbine rotor and generator rotor journal and cylinder joint surface repair; boiler four-tube wear-resistant and anti-corrosion coating; water turbine blade anti-cavitation wear-resistant coating; gas turbine blade, flame tube, transition section High temperature protective coating; fan Impeller, ball mill and other abrasive wear-resistant coatings; door core, door stem, valve core, valve accessories, valve seat wear-resistant anti-corrosion coating and boiler-related equipment parts reinforcement and repair. More successful cases can be seen: Su Rui series: arc spraying powder core wire series products

6. Transportation

Wear-resistant coatings for various wear areas; repair and pre-reinforcement of automotive engine blocks, synchro rings, rollers; gearbox bearing blocks, cylinder plungers, front and rear axle support shafts, door frame guides, engine main pad seats, rocker arm shafts, Wear-resistant coating on the oil seal position of the half shaft, pin shaft wear; excavator rake head, wear-resistant ring, mud bucket, torsion blade, shovel tooth, mud pump impeller, stern shaft, Quzhou copper sleeve, eccentric shaft sleeve, gear transmission Shaft, mud pump water seal neck, mud door, sliding plate, scraper scraper scraper wear-resistant coating.

7. Chemical industry

Repair of various vessels, reactors, pipes, pumps, valves and seals; repair of various enamel tanks, special vessels for on-site repair; repair of boilers, air compressors, pumps and other components.

8. Glass industry

A layer of ceramics is sprayed on the surface of the lifting roller and the conveying roller by thermal spraying, which improves the corrosion resistance of the lifting roller and the conveying roller to the molten glass and inhibits the adhesion of the molten liquid phase on the surface of the roller. Slow down the erosion of molten glass on the roll surface and make the roll surface smooth for a long time. Reduce maintenance of lift and conveying rollers, improve glass quality and productivity, and reduce production costs.

9. Electrical wires

The supersonic flame spraying technology is used to spray the carbide ceramic coating on the drawing tower wheel, wire drawing machine, wire drawing wheel, wire drawing drum, wire take-up disc, guide groove and other parts, so that the surface hardness can reach HRC75, which is higher than that of wear-resistant steel or colder. Hard steel is much taller. High wear resistance; the base body of these parts can also be made of ordinary steel or cast iron, which not only reduces the cost but also prolongs the service life.

10. Municipalities

All kinds of steel structure thermal spraying long-term protective coatings, anti-corrosion, long-term anti-corrosion, protection life of up to 30 years.

11. Light Industry

Plastic mold spray reinforcement; extrusion molding machine screw and rubber mixer rotor spray reinforcement; various roller bearing parts spray reinforcement.

12. Steel industry

The extreme working conditions in the steel industry often lead to different wear on different parts. Over the past decade, we have done a lot of research to improve the efficiency of steelmaking. Thermal spraying has proven to be an effective solution in the past and we are now looking at wider applications in this industry.

The extreme working conditions in the steel industry often lead to different wear on different parts. Over the past decade, we have done a lot of research to improve the efficiency of steelmaking. Thermal spraying has proven to be an effective solution in the past and we are now looking at wider applications in this industry.

13. aviation

In aviation, there is a huge potential for wear and tear on engines. Many of its moving parts are in contact with each other or some of the fixed contact parts change suddenly. It is a very complex mechanical part. To this end, the aviation industry has become one of the first industries to fully adopt thermal spraying. They use thermal spray aircraft engines to optimize their performance, safety and reliability.

Most engine systems are: fan blades, compressor, combustor, high pressure, low pressure turbine and exhaust. The engine design includes a non-rotating system and two coaxial selection systems. A non-rotating (stator) system consists of a structural frame and a housing. The low-pressure rotating system consists of vanes, vanes, low-pressure turbine disks, turbine blades and connecting shafts. The high-pressure rotating system consists of high-pressure turbine discs/buckets, compression vanes, turbine vanes and connecting shafts. Different parts of the engine work in different environments, depending on the task the engine is to perform. The temperature is below zero to 1095°C (2000°F), the rotational speed can reach 15,000 rpm, and the bearing load of the rolling bearing is from several MPa to more than 1720 MPa. As the rotor slides around the stator, the slip ranges from a few inches to a few inches at zero degrees, otherwise the vibrations will cause relative motion between the parts, causing the mechanical parts to collide with each other. Various components are also affected by the spray material. Different working environments will use different spraying materials and spraying processes to meet the design requirements of the engine. 

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