Since the beginning of the application of jet engines, people have been constantly striving to improve the performance of the engine. The high performance and environmental adaptability requirements of jet engine thrust and fuel consumption ratio are higher year by year.
In order to meet (accommodate) these high-performance requirements, higher requirements have been placed on the weight of the engine itself, the high temperature of the turbine engine, and the high pressure of the compressor, and a large development in production technology is also required. Production technology determines competitiveness, and surface modification technology is the key to competitiveness.
(1) Surface modification (functional film formation) technology has been developed in the development of new materials, surface modification (functional film formation) technology development, cooling structure design and production technology development in order to adapt to high temperature.
In the aerospace industry, functional film forming technologies on metal parts such as jet engines include CVD, PVD, electroplating, spraying, surfacing, etc. The disadvantages of these technologies are large equipment investment, strong dependence on skills, and some processes. It is necessary to add a pretreatment process such as cleaning and masking, and a post-treatment process such as mask removal and boundary treatment, and some problems such as thermal deformation and peeling of the film body are not suitable for the production of the line.
(2) New functional film forming technology
IHI and Mitsubishi Electric have developed a new forming technology that can be integrated into the machining line to produce various functional films, namely a new technology for coating mold and tool processing surfaces based on the discharge coating technology. With this new coating technology, a cermet film, a thick metal build-up layer, and a mixed layer of cermet and metal can be formed. Since the discharge energy is utilized, it is called an MS coating (micro-arc coating). Based on this technology, functional thin films or surfacing layers suitable for various components have been developed.
MS coating technology
MS coating technology is a high-quality functional thin film technology that uses an electrode containing a component such as a metal or a ceramic to perform a discharge surface treatment to form an excellent durability and wear resistance. Because it does not require skilled operators and pre- and post-processing procedures, it is suitable for automated production lines; and because it does not require expensive evaporation furnaces and other equipment, the manufacturing process is simplified and the cost is greatly reduced.
(1) Principle of MS coating
The electrode made of the coating material powder and the material to be treated are placed in the insulating oil to apply a voltage. At this time, the pulse discharge is started between the electrode and the material to be processed (about 10,000 times per second), and the electrode material gradually migrates to the substrate. Melt bonding to form a thin ceramic coating or a thick metal build-up layer. By selecting different electrodes and processing conditions, a dense or loose or porous coating structure can be formed.
(2) Main advantages of MS coating The main methods of metal surface coating are surfacing, spraying, electroplating, etc. MS coating has the following advantages compared with these methods (see Table 1).
Table 1 Comparative characteristics of MS coating and other technologies: MS coating - electroplating - surfacing - spraying integrated in the production line: easy - difficult - difficult - difficult costs: small - large - medium - large pre-order processing: almost no need - Mask protection - need to finish - mask protection quality: stable - peelable - crack - peeling deformation: no - no - large - coated material: ceramic, metal - metal - metal - ceramic, metal environment: â—‹ -â–³-â–³-â–³
1The base body is extremely deformed and has no cracks.
When the welding is performed, the thermal expansion and contraction of the welded portion is large, and deformation and cracks are easily generated. When the MS coating is produced, a micro-stage micro-pulse discharge is generated, and since the partial fusion is repeated at the local portion, the shrinkage of the substrate is restricted, so that the deformation is small and there is no crack.
2 The coating film does not peel off When the metal is adhered to the surface of the substrate by spraying, plating or the like, there is a possibility of peeling off, and the MS coating is melted and joined without causing peeling.
3 can be processed at the required position, no need for pre-treatment process. Since the MS coating only forms a coating at the discharge of the electrode and the substrate, it does not require pre-treatment processes such as masking and protection for processes such as spraying and plating.
4 Independent of the skills to ensure reliable quality Traditional welding operations, in order to ensure the quality, skilled workers need to work manually, and MS coating equipment, without relying on skilled workers, can ensure reliable quality.
5 The establishment of small-scale production lines has made it possible to form a production line with large scales of spraying, electroplating, etc., while the MS coating equipment is small in scale and can easily form a production line.
Application examples and applicable applications
Some applications of MS coating technology in jet engines are being tested, and some have been verified on the aircraft.
(1) High temperature wear resistance example
A chromium-containing cobalt alloy is deposited on the friction surface of the low pressure turbine moving blade flange. When using the welding process, a large amount of margin must be removed manually. The MS coating can be deposited into the required thickness dimensions without further processing.
From the comparison of the wear conditions of the deposited layer by the conventional welding method and the MS coating method, it can be seen that the MS coating does not have much wear from low temperature to high temperature.
Test conditions: surface pressure: 7 MPa; amplitude: 1 mm; number of rubs: 1 million times.
Parts coated with TiC coatings using MS technology are much more wear resistant than the same parts that are not coated.
(2) Examples of wear resistance
1 A 0.7 mm thick sealed end of the low pressure turbine moving blade flange is coated with cermet. When the coated part is rubbed against the honeycomb sealing part of the stationary part, when the honeycomb sealing has a certain degree of wear, the coating part is not worn, and there is wear when there is no coating, and the metal material is transferred on the honeycomb.
2 The inner surface of the end of the compressor rotor blade is coated with a 15μm thick cermet, and the seal with a thickness of 0.3mm for the air seal is coated with a cermet. When there is friction, only the sealing portion of the stationary part is worn and there is no wear on itself. Since the engine performance is degraded after the end of the blade is worn, periodic inspection and surfacing repair are required. After the MS coating is used, the frequency of the surfacing repair is greatly reduced.
(3) Surfacing repair example
1 The end of the compressor rotor blade made of nickel alloy is welded with a 0.4 mm cobalt alloy. The leading and trailing edges of the blade are only 0.2 mm thick, but they can be welded with a 0.4 mm thick cobalt alloy.
2 0.4mm cobalt alloy was deposited on the front end of the unidirectional solidified nickel alloy material turbine motorized blade. It is very difficult to weld on a unidirectional solidified material. There must be no weld cracks and the concavity of the front end portion is required. Micro-arc surfacing is a feasible process.
3 The low-pressure turbine of the nickel alloy is welded with a 0.4 mm cobalt alloy on the side of the groove at the position of the stationary blade. Even for narrow trenches, micro-arc surfacing and coating can be performed as long as the electrodes are accessible.
4 Use a small electrode on the outer circumference of the nickel alloy workpiece to perform uniform metal surfacing on the rotating workpiece. It is also convenient to repair the finished workpiece that does not allow deformation.
(4) Example of coating of the shaft
Using a small electrode to rotate the workpiece, the cermet can be uniformly coated on the outer circumference of the nickel alloy. After coating, the surface hardness of the workpiece can reach HV2000, the wear resistance is improved, and the metallographic structure is not changed.
IHI is promoting MS technology in the field of jet engines. It is especially suitable for jet-starting parts that are resistant to high temperatures, high pressures and high-speed rotation.
The MS coating technology developed by Mitsubishi Electric and IHI Co., Ltd., in the field of aerospace, where the introduction of European and American technology is dominant, has enabled Japan to have coating technology with independent intellectual property rights. Next, the company plans to expand into areas such as automobiles and generators.
The development, manufacture and sale of MS coating technology is undertaken by Mitsubishi Electric.
A captive bolt pistol (also variously known as a cattle gun, stunbolt gun, bolt gun, or stunner) is a device used for stunning animals prior to slaughter.
The principle behind captive bolt stunning is a forceful strike on the forehead using a bolt to induce unconsciousness. The bolt may or may not destroy part of the brain.
The bolt consists of a heavy rod made of non-rusting alloys, such as stainless steel. It is held in position inside the barrel of the stunner by means of rubber washers. The bolt is usually not visible in a stunner in good condition. The bolt is actuated by a trigger pull and is propelled forward by compressed air or by the discharge of a blank round ignited by a firing pin. After striking a shallow but forceful blow on the forehead of the animal, spring tension causes the bolt to recoil back into the barrel.
The captive bolt pistols are of three types: penetrating, non-penetrating, and free bolt. The use of penetrating captive bolts has, largely, been discontinued in commercial situations in order to minimize the risk of transmission of disease.
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