The thermal spraying material and coating function and application
A: thermal spraying materials
Has been realized in the practical application in industrial production of coating materials such as metals, alloys and ceramics, mainly used in powder, wire and bar state, including spraying powder for spraying materials more than 70% of the total amount. Used as a coating material are:
1, thermal spraying powder
Pure metal powder: W, Mo, Al, Cu, Ni, Ti, Ta, Nb, etc
Alloy powder: Al - Ni, Ni - Cr, Ti, Ni, Co - Cr - Ni - Cr - Al, W, MCrAlY (M = Co, Ni, Fe), Co, Ni, Fe base metal, etc
Oxide ceramic powder: Al2O3, ZrO2, Cr2O3, TiO2, etc
Carbide powder: WC, TiC, Cr3C2, etc
Metal ceramic powder: WC - Co, Cr3C2, NiCr, etc
Plastic powder: nylon, polyethylene, PPS etc
2, thermal spray wires
Al, Cu and zinc, Sn, Al - zinc alloy, babbitt alloy, stainless steel,
Ni - Al wire, etc.
3, thermal spray bar
Al2O3, ZrO2, Cr2O3, etc
B: coating functions and applications
1, antiwear coating
Wear industry equipment damage is one of the main reasons that may lead to abrasion working conditions including micro vibration, sliding, shock, abrasion, erosion, etc. Wear resistance coating should be hard, but also the performance of the heat resistance and resistance to chemical corrosion. Fe, Ni, Co in the metal and WC - Co and Cr3C2 - NiCr metal ceramic, Al2O3 and Cr2O3 ceramic material has these properties. The coating technology improve the surface wear resistance has a very wide range of applications, such as piston ring, the gear synchronous ring spraying Mo coating, textile machinery parts and components such as roller, spinning hook on the spraying and fiber resistance of Al2O3, Al2O3 and TiO2 ceramic coating, pump and valve sealing surface coating Cr2O3, WC - Co wear-resistant coating, high power and large truck crankshaft mill, exhaust fan shaft using Fe base alloy material repair wear and abrasion resistant reinforcement, etc.
2, anticorrosion coating
Long exposure to outdoor atmosphere (Marine, industrial and urban and rural atmosphere) and different medium (water, river water solvent and oil, etc.) in the environment of large steel structures, such as power transmission tower, steel structure bridge, offshore drilling platform, derrick in coal mine, and all kinds of chemical containers such as storage tanks, etc., by different degree of oxidation and erosion environment. With Al, zinc, and Al - zinc alloy and stainless steel protective coating, can obtain long-term protective effect for 20 years. Some components by gas corrosion and chemical corrosion, can according to the specific conditions (such as the medium, concentration, temperature, pressure, etc.) select the appropriate coating materials such as metals, alloys, ceramics and plastic for protection.
3, high temperature oxidation and hot corrosion resistance coating
For some exposure to high temperature corrosion in the gas components, by high temperature, gas corrosion, and the function of air flow scouring, seriously affected the life and safe operation of the equipment. In addition to high temperature oxidation and hot corrosion resistance of materials must be resistant to high temperature oxidation and corrosion, must also have similar to the substrate material coefficient of thermal expansion, the party won't be caused by local overheat temperature cycle and the coating thermal fatigue performance degradation. Used as high temperature oxidation and hot corrosion resistance of coating material has: NiCr, leicester, MCrAl, MCrAlY (M = Co, Ni, Fe) and Hastiloy and Stellite alloy, etc. This kind of coating of four typical applications such as power plant boiler tubes (water wall tube, reheater and economizer, superheater tube) and water wall of high temperature oxidation corrosion has been electric power, papermaking, chemical industry and other industrial boiler users need to solve the problem, after years of research and practice has proved that the electric arc spraying Ni - Cr, Fe - Cr - Al and Ni - Cr - Al, 45 ct coating can achieve a good protective effect, the service life of up to nine years. MCrAlY coating used in aviation turbine engine blade coating as well as turbine engine combustion chamber, such as flame tube with a thermal barrier coating bonding layer.
4, thermal barrier coating
ZrO2, Al2O3, ceramic coating, such as high melting point, low thermal conductivity, under the condition of high temperature of substrate metal has good heat insulation protection is called thermal barrier coating. The coating generally consists of two systems, one is by metal bottom, another is make by ceramic surface. Sometimes in order to reduce the difference in thermal expansion between the metal and ceramic and the stress distribution of coating was improved, often in the bonding layer and add a transition layer between ceramic surface, the transition layer or by the underlying metal and surface ceramic materials with different mixing ratio of multilayer coating or grounds of metal and ceramic material composition composition of continuous change of the coating to form the so-called gradient coating (or function). Metal bonding layer as Co and Ni, Cr, Al, Y alloy material, ceramic material had better use by Y2O3 and stable ZrO2, thermal barrier coatings are used for diesel engine piston, turbine engine combustion chamber, valve and flame stabilizer and so on.
5, insulation coating
Ceramic material has not only high hardness and good wear resistance, but also has very good insulation performance, USES the high energy of plasma spraying Al2O3 coating density, high dielectric strength, is the ideal insulation coating. If the use of organic or inorganic epicuticular spray hole sealing layer again, and will get more good insulating effect. The current height of the insulation coating has been used in polymer thin film for corona discharge roller surface activation treatment, the effect is good
6, clearance control coating
With composite powder, spraying soft wear seal coating on substrate in aviation and aerospace industry is rapidly developed high temperature sealing, accused of gap technology, is one of the important application in the field of modern thermal spray coating. In the mating parts contact with can wear coating is made of two kinds of powder mixed powder or reunion, prepared by flame or plasma spraying. In general, can wear coating is composed of ontology metal and non-metallic filler, filler is usually graphite, polyester, boron nitride etc. The function of packing is weakened the integrity of the coating itself and thus enhance coating can wear. Has developed a series of spray can wear coating material, the air on the surface of the coating used in sealing parts, compressor, or between turbine blade and metal surface structure or machine brake, won a good sealing effect. Can wear also can be used in the labyrinth seal coating, the coating used for cooling air channel, reduce the loss of the compressed air engine, and maintain the pressure balance of the rotor shaft.
7, size coating recovery
Thermal spraying is to restore parts size of an economic and effective method. Whether it's because of work wear and tear or caused by processing of the workpiece size don't meet requirement, all can be reinstated using thermal spraying technique. When this method is neither welding deformation problems, also not as expensive as special plating process. At the same time the new surface can be made of wear resistant and corrosion resistant material, can also be the same as the composition of workpiece materials. Repair all kinds of axial plunger and is a typical application, including his shaft, motor shaft, reciprocating plunger, journal, roll, paper dryer and pump impeller blade and the shell of petroleum and chemical industry, etc. Generator faceted field thermal spraying in the cylinder repair is thermal spraying recovery plane a successful application example of workpiece size. Generator cylinder in the long-term use of faceted due to micro vibration, corrosion and erosion of hot gas flow and several different shapes, different area range and depth of damage, leakage and affect the efficiency of generator. Thermal spraying methods respectively to spraying to fill the damage, and then through grinding cylinder plane healing and achieve the required dimensional accuracy. Thermal spraying technology can yet be regarded as the weight of large, complex and expensive cylinder split the security at the site (not happen deformation), simple and efficient method.
8 and biological function of coating
In stainless steel or titanium substrate spraying biological functional ceramic coating, such as hydroxyapatite, can effectively overcome the metal type artificial bones and organism tissue fluid corrosion problems and incompatibility, and can improve the body's tissues and the combination of artificial implants.
9, far red radiation coating
Some oxide with a high rate of thermal radiation, when heated to radiate far red wave, the wave's energy to be macromolecule organic matter (such as paint), water, air and other molecular absorption of the materials to produce resonance and internal heat generation, so as to accelerate the process. Spraying the coating on heating element, its energy-saving efficiency generally in 25 to 40% on average.