Process control, environmental control, hydraulic and pneumatic equipment, servo valves and transmission, chemicals and chemical industry and medical instrumentation and many other fields.
Thermal spraying of high temperature resistant ceramic coatings can best reflect the characteristics of thermal spraying technology, the application of the most prominent effect, is the most influential
an application area.
1. Thermal Barrier Coatings (TBCs)
The heated parts of gas turbines, such as blades, nozzles and combustion chambers are in a harsh environment of high temperatures, oxidization, and high-speed gas flow erosion
. For gas turbine components subjected to temperatures as high as 1,100 °C, the temperature limit for the use of nickel-based high-temperature alloys (1,075 °C) has been exceeded. Effective way is to coat the adiabatic good high melting point ceramic coating for high temperature alloy base
body wearing "fire armor", play the role of adiabatic shielding. This is called thermal barrier coating.
The basic requirements of the thermal barrier coating are: (1) high temperature resistance; (2) resistance to high temperature oxidation; (3) combined with the metal substrate is strong;
(4) low thermal conductivity, good insulation; (5) coefficient of thermal expansion and the metal substrate to match the number of heat cycle is high. Practice has shown
that the use of MCrAlY alloy as a bonding substrate, spray Y2O3 partially stabilized ZrO2 adiabatic ceramic coating, the coating is hard
hard, dense, and has excellent resistance to high-temperature gas erosion and thermal shock, and its thermal
stability and chemical stability are very good even when used for a long period of time at high temperatures up to 1,650 ℃. The addition of a small amount of CeO to Y2O3ZrO2 can further improve the coating. A small amount of CeO in Y2O3ZrO2 can further improve the thermal shock resistance of the coating
performance. In the case of a somewhat lower operating temperature, MgO or CaO-stabilized ZrO2 can be used as the thermal barrier ceramic barrier
layer.
Pre-oxidation of the bonding substrate for thermal barrier coatings, aluminizing of the thermal barrier ceramic coatings, laser remelting modification of the surface
ceramic coatings and the development of multilayered or gradient functional coatings are
some of the latest developments in the field of thermal barrier coatings.
The thermal barrier coatings are mainly used in the heated parts of aviation, naval and land-based gas turbines, and are now being popularized in the fields of civil
internal combustion engines, pressurized turbines, and oxygen injection guns for the metallurgical industry.
2 abradable sealing coating
Modern aviation engines use pressurized air to pressurize and heat up, high temperature compressed air into the combustion chamber to make fuel charging
Separate combustion is to improve the power of the engine and one of the main measures to improve thermal efficiency. Thermal spraying technology in the compressor volute
internal surface spraying abradable sealing coating, and the hard coating of the compressor blade tip to form a pair of abradable sealing wear
vice, in the process of operation can form the ideal radial air gap, to obtain the maximum pressure difference, thus significantly increasing the engine
engine power, reduce the consumption of aviation gasoline, and improve the whole engine. A test vehicle pass rate. This is the thermal spray technology
in the field of aviation engine one of the major application results.
With the step-by-step increase in compressed air temperature, the use of abradable seal coatings from 300 ℃ to 1100 ℃,
modern abradable
consumptive seal coatings have reached a maximum temperature of 1,350 ℃. AlSi-polyphenylene grease, nickel/graphite, Ni/diatomaceous earth, NiCrAl/BN,
Y2O3
．ZrO2-BN, ZrO2-BN, ZrO2-BN, and so on. >ZrO2-BN and other composite powder series materials have been successfully applied. Among them, especially high-temperature abrasive sealing coating
layer of the most severe working conditions, to withstand high temperatures of 1,000 ~ 1,350 ℃, subjected to 2 ~ 3 times the speed of sound of the high-temperature gas flow
erosion, subjected to more than 300 m / s linear velocity of the tip of the blade scraping without spalling. Therefore, in addition to must have
high-temperature coating should have high temperature, oxidation, heat shock, chemically inert, combined with strong performance, its most
main feature is the soft (usually coated surface Rockwell hardness of 50 ~ 80 HR15Y), porous (porosity of about 25%
~ 30%).
The thermal spray abradable seal coating technology can be used in civil
industrial applications such as gap control of rotating pressurized gas components in the compressor industry.
3 Anti-temperature adhesive wear coatings
Annealing furnace rolls, heat treatment furnace rolls, continuous casting machine tension rolls, support rolls, sintering furnace rolls and other high temperature rolls, more in
800 ~ 1 200 ℃ high temperature operation. At such high temperatures, the steel softens and generates iron oxide scales on the surface, while the furnace
roll's high temperature hardness is also significantly reduced. When the soft state of the high-temperature steel parts, especially the steel strip in the furnace roll movement or even slight sliding
, it will be due to high-temperature adhesion and produce nodules, this nodules in the role of shear force off for abrasive, so that the steel parts (with)
surface to produce scratches, scratches, furrows, depressions and other defects. These defects in the subsequent surface light rolls are often difficult to
eliminate, will ultimately affect the quality of hot rolled steel strip.
The use of high-speed gas flame spraying (HVOF), explosion spraying (DGS) or plasma spraying technology, high-temperature furnace rolls
surface spraying of special ceramics or cermet coatings, with excellent high-temperature resistance, oxidation resistance, anti-adhesion, anti-tumor and
Self-cleaning cleaning purification performance, not only to significantly improve the service life of the rolls, but also the production of surface finish quality Excellent steel,
such as high-quality silicon steel plate, high-quality automotive sheet and hot-dip plating sheet. Hot rolled stainless steel strip annealing furnace rolls, sprayed with BN
metallic ceramic coating, its resistance to high-temperature wear and tear performance can be increased by more than four times.
In Japan, the iron and steel industry, the application of thermal spray technology is the main object of various rolls, thermal spraying of the rolls accounted for all
Thermal spraying of more than 85% of the parts, with extremely significant technical and economic results. Such as annealing furnace guide roller, the past average monthly
downtime maintenance 30 min, after spraying can be maintained for 3 years without maintenance, and greatly improve the quality of steel strip. Japan Steel
Iron Company thermal spray annealing furnace roll rate, from 20% in 1982 rose to 100% in 1989, while the strip due to tuberculosis
and other causes of scrap rate fell from 80% to 0.
4 anti-temperature molten metal or melt erosion coating
A variety of metal smelting furnace lining materials, basically ceramic Refractory materials, this is because it not only has a melting point
high, high temperature chemical stability and other characteristics, but also has a small angle of wetting with the melt, or even non-wetting characteristics. The use of these
These characteristics, used in the melt pool of metal parts such as hot dip plating tank immersion rollers, stabilizer rollers, melt pool agitator,
blow pipe, thermocouple casing, hot die casting molds and other surfaces, spray refractory ceramic or metal ceramic coatings, can be obtained
Excellent performance of the resistance to high temperature molten metal or melt erosion coating. For example, hot dip aluminum plating tank sinking rolls and stabilizing rolls,
Because of the aluminum liquid has a very high chemical activity, and a variety of metal aluminum thermal reaction to form intermetallic compounds, known as
for the metal of the "solvent". Therefore, the metal alloy furnace roll in the aluminizing tank corrosion is very fast, the service life of only 5 ~ 10 days.
The use of thermal spraying special ceramic coating, the Germans believe that the only effective solution, the service life can be increased to 20
~ 30 days.
5 anti-corrosion wear
Petroleum, chemical, pharmaceutical, paper, printing and dyeing, metallurgy, building materials, marine development, environmental protection and other sectors used in many
Many mechanical equipment, due to a variety of chemical media, corrosive gases and seawater, etc., corrosion, corrosion products
become abrasive grains, with foreign particles or dust, or media production process Crystalline crystals together, are able to make the relative movement
between the surfaces of mechanical parts both corrosion and wear. Abrasive metal surface to produce "plow
wrinkle", "scratch" and bare newborn surface to accelerate corrosion, corrosion products become abrasive particles to accelerate wear. Because of the corrosion
and wear and tear at the same time play a destructive role, promote each other, and accelerate the premature failure of such mechanical parts, and even brew
into a major accident.
In the corrosive wear conditions, stainless steel or titanium alloy corrosion resistance is good, but not wear-resistant. Industry widely
used hard chrome plating, but hard chrome plating there are three major shortcomings:
(1) long process, more processes, covers an area of large, low deposition rate, difficult to deposit thick coatings.
Material Protection 990119
(2) Above 260 ℃, the chromium plating layer will be softened, and the abrasion resistance is significantly reduced. Local oil-free critical lubrication or abrasion
Grain scratches will cause the plating layer to appear localized overheating and softening, pulling into grooves;
(3) Environmental pollution. Chromium plating in the production of several environmentally hazardous toxic waste (such as hexavalent chromium, etc.) aggravate the pollution of water, soil
soil and air. Most of the chromium compounds contain strong carcinogens, and their toxicity is four orders of magnitude higher than that of methyl chloride, which has been banned from use in most industries
. Obviously, replacing electroplated hard chrome technology as much as possible has become a pressing task
.
Thermal spraying of ceramic coatings and metal-ceramic coatings not only has a high hardness, excellent corrosion resistance, and friction
number of small, low energy consumption, the sealing filler wear is small, the hardness of the coating and abrasion resistance will not be reduced because of local overheating.
Therefore, it is becoming the strongest competitor and replacement of electroplated hard chrome technology in the field of corrosion and wear resistance. Large reservoirs, water
power stations and marine development with hydraulic cylinders for hydraulic opener large piston rod, the use of plasma spray ceramic coating instead of plating
hard chrome, can achieve high quality, long life, maintenance-free, in Germany has become an advanced manufacturing technology in this field,
has manufactured 16 m long, weighing 10 t or more of the ultra-large ceramic coated piston rods and the corresponding of the hydraulic opener. Hydraulic piston rods for large bulldozers, hydraulic piston rods for steel rolling mills, hydraulic machine piston rods for architectural tile presses, impeller shafts and wear rings for water turbines, armature heads, grinder shafts, fuel pump shafts, anti-seize bushings, piston rings, cam followers, etc., can be coated with ceramic or ceramic in almost all original chrome-plated products in the case of low stress sliding wear and corrosive working conditions. Thermal spraying ceramic
or cermet coating instead.
6 fiber wear-resistant coatings
6.1 Textile fiber wear-resistant ceramic coatings
Modern textile machinery, especially chemical fiber machinery, to high-speed, lightweight, energy-saving direction. Spinning process, all kinds of
guide, spinning parts, in order to reduce the weight, increase speed and reduce energy consumption, more than the use of aluminum alloy manufacturing, its surface
surface suffered a very fine high-speed chemical fiber filament (up to 700 ~ 1,000 m/s) wear and tear and the formation of grooves, replacement not only caused by the loss of shutdown
loss, but also affects the spinning of the quality and grade.
In the chemical fiber spinning machine, the surface of the guide parts, the use of plasma spraying Al2O3-based composite ceramic coatings, after treatment to obtain
Orange peel-like "appearance of the morphology, to achieve Ra about 1.5 μm surface roughness. The outstanding features of this ceramic coating
are:
(1) excellent resistance to high-speed fiber abrasion, service life than the chrome-plated parts increased by 5 times;
(2) moderate friction, can be applied to the fiber with the right amount of "twisting force", so that the fibers to achieve the necessary strength and
toughness;
(3) the fiber is not a good choice for the surface roughness, but it is a good choice for the surface roughness of the fiber, so that the fibers can be used for the surface roughness.
Toughness;
(3) moderate surface roughness, can make the fiber to obtain the necessary "velvet", to achieve good dyeing performance, have
a certain degree of moisture absorption.
Because of these characteristics of the ceramic coating, so that the life of the key basic parts of chemical fiber machinery than the original chrome-plated parts to improve
5 times, the production has reached a new level. The Czech Republic to apply this technology, so that its chemical fiber machinery exports more competitive
competitive.
6.2 Resistant to metal drawing wear coating
Metal drawing industry such as steel wire, steel wire rope and wire and cable production use a large number of wire guide wheel and roll. Metal
Wire in the surface of high-speed sliding and cold hardening, the guide wheel contact surface produces strong friction wear, so that the production
Generated "plow furrow", pits and other defects, resulting in a low life expectancy, replacement of the frequent maintenance and impact on the quality of the drawings and other drawbacks.
Using
supersonic flame spraying or explosion spraying technology, in the metal wire drawing guide wheel surface spraying containing Wc of cemented carbide coatings, with
high hardness and wear-resistant properties, life expectancy increased by 5 to 10 times, and has achieved great success.
6.3 hydrophilic and dielectric coatings
Modern paper and printing machinery, despite the high operating speed, but because of the light load, so they are in a low stress state,
special application of thermal spray coating.
Plasma spray ceramic coating technology, paper and printing presses in foreign rolls have been successfully applied for many years, the application
face is increasingly expanding, this is because the ceramic coating has many features: high abrasion and corrosion resistance; high selective wettability, hydrophilic
water; high electrical insulation and dielectricity; high anti-adhesion; high etchability and clarity of the pattern; to maintain a moderate roughness of the
Paper bite, and so on.
For example, color offset printing machine water roller spray ceramic coating, not only wear-resistant, ink corrosion resistance, and left after etching
ceramic coating part, due to good hydrophilicity, it can be formed on the surface of a thin film of water, to prevent the ink from mixing, no
ceramic coating of the etched roller surface is covered by the ink, and thus obtain a clear image of the color prints, do not string colors. Also
such as plastic film electro-etching with corona processor rollers, need to run at 1 ~ 2 × 104 V. Roller surface spraying high dielectric
Ceramic coating to meet this need.
The surface roughness of the plasma sprayed ceramic coating, spraying about 2 to 5 μm, grinding up to Ra 0.13 to 0.20
μm, fine grinding up to 0.03 to 0.10 μm, which can meet the needs of different grades of paper production.
From the above applications, thermal spraying of high-performance ceramic coatings has a broad market and huge economic
benefits.
In the field of high-tech applications and potential prospects
Thermal spraying of high-performance ceramic coating technology, high-tech fields are emerging, it will drive and promote a series of
The development of high-tech technology and the emergence. High-temperature superconductor parts with high critical resistance temperature of the composite oxide superconducting ceramic material discovery, is the material field in the 80's
major breakthroughs. Yttrium barium copper oxide superconducting ceramic material of zero resistance temperature tc>90 K (higher than the temperature of liquid nitrogen), the magnetic transition temperature tB>
96 K.
Plasma spraying superconducting ceramic coatings have the unique advantages of: high deposition rate, easy to prepare a thick coating and a large area
coating, able to spray superconducting parts with complex shapes, can be directly in the atmosphere, no protective gas is required. Spraying directly in the atmosphere, without protective gas, is
promising process to realize the practical realization of superconducting materials. Plasma spraying yttrium barium copper oxygen (YBaCuO), bismuth strontium calcium copper oxygen
(BiSrCaCuO) superconducting ceramic coatings have been successfully reported. In magnetic shielding, microwave components, various types of sensing
devices, quantum electronic devices, etc., showing good prospects for application.
The use of plasma spraying technology to manufacture targets for sputtering, such as yttrium-barium-copper-oxygen
(YBa2Cu3Ox) targets for physical vapor deposition (PVD), is capable of producing high-performance superconducting thin films, with critical current densities as high as 105 to 106 A/cm2.
6.4 In microelectronics industry
Metal-ceramic composites are an ideal material for substrate materials in the microelectronics industry. By thermally spraying insulating ceramic coatings on metal plates (e.g., Kovacs
gold, copper, aluminum, and steel), the metal, with its high thermal conductivity, is able to dissipate the heat
generated by the strong electric current, while the ceramic coatings provide excellent dielectric insulation properties. Spraying Al2O3 ceramic coating on a copper plate, for example,
the total thermal conductivity than the same thickness of copper sintered alumina layer on the total thermal conductivity of 5 times higher, which is very conducive to the integrated electrical
Road board heat dissipation and improve power. The United States has been able to spray 25 mm × 25 mm dielectric ceramic coated composite circuit boards, and reached
to 5 × 104 pieces of mass production scale.
6.5 Biomedical functional ceramic coatings
The improvement of people's living standards and the average life expectancy of human beings to prolong the need for artificial bones is increasing.
Previously, the use of stainless steel or titanium alloy and other metal skeleton, implanted in the body to replace the damaged bone, but there are
resistant to body fluids corrosive insufficient, and muscle cell tissues do not affinity and produce water retention and other problems.
Modern research has shown that the crystals that make up the hard tissues of living organisms are apatite-based inorganic ceramic materials.
Plasma spraying of biomedical functional ceramic coatings on metal substrates has the following characteristics: (1) non-
toxic to living organisms, suitable for in vivo safe use; (2) good adaptability and affinity for living organisms and cells, will not produce side effects
; (3) corrosion-resistant to human bodily fluids; (4) resistant to wear and tear in the course of long-term use; (5) has the mechanical properties such as strength
degree and toughness necessary for human movement; (6) the porous and rough surface of the sprayed layer is conducive to the growth and affinity of the tissues of living organisms to the surface of the artificial skeleton
surface. Therefore, thermal spraying metal-based bioceramic coating of artificial bone, is more ideal artificial
bones material, has been in the human femur, hip, elbow joints, pelvis, artificial teeth and other aspects of the clinical application of the test success
success, the Americans called "medical biofunctional materials of a revolution."
Thermal spraying of high-performance ceramic coating technology, in foreign countries has been a fairly wide range of applications and outstanding benefits of high
new technology, in our country has just begun. Admittedly, there is no "stone into gold", "clay into gold" magic formula, but the adoption of
Thermal spray ceramic coating technology, with little material consumption to obtain high value-added, to open up a huge potential market, undoubtedly
could achieve twice the result with half the effort!
We can achieve twice the result with half the effort.