Application of laser welding in engine overhaul

Laser processing is a high-temperature thermal processing technique that uses a high-radiation intensity laser beam to focus through an optical system (a power density after focusing can reach 10*4~10*11w/cm2). The energy of the laser beam can completely melt the high melting point phase, inclusions, and the like in the alloy. Laser processing can be carried out in the atmosphere or in a vacuum. For some special alloys (such as titanium alloys), it is not necessary to perform laser processing under vacuum, and only a protective gas (ammonia or nitrogen is used for nickel-based alloys and alloys). The melting zone of the matrix material can be limited to a few tens of microns, or even a thinner range. The thickness of the heat affected zone produced by the laser cladding layer is approximately 1/10 (0.10-0.25 mm) of the thickness of the deposited layer, which means that the heat affected zone is narrow. >> Into the colorful world of laser welding  

Advantages of laser cladding and welding technology

Laser cladding is mostly used for resizing of engine components. Compared with other forms of surfacing, the advantages of this technology are concentrated in the following aspects.

(1) Laser cladding processing has high precision and is easy to achieve near net shape and subsequent finishing. If TIG surfacing is used, the width and height of the surfacing are not easy to control, the subsequent finishing allowance is too large, and the heat affected zone is large.

(2) Laser cladding processing is easy to digitize and can process parts with complex geometry. If manual welding is used, the requirements for stability and quality cannot be met.

(3) Using high-efficiency automated laser cladding technology, it can effectively reduce the heat affected zone and reduce the generation of blade cracks. The first pass rate of the product can be stabilized above 95%, while the traditional standard process (TIG surfacing) is used. The difference is very far.

(4) Laser cladding can be carried out under hydrogen protection without the need for a vacuum environment. Compared with electron beam surfacing, the processing efficiency is higher and the equipment maintenance is more convenient.

Foreign application status

Laser cladding technology is mainly used for repairing parts of aero-engine turbine blades, guide vanes and pneumatic seal systems. The following are some of the applications of laser cladding technology by some foreign companies.

(1) British Luo-Ro Company

The application of laser cladding in the manufacture of hot-end components for gas turbines should be the first to be promoted by Luo Yiluo. In 1981, the company used this process to strengthen the drill-base wear-resistant alloy coating of the RB211 engine turbine blade crown damping surface. Under the auspices of Luo Yiluo Company, the University of Nottingham has developed a blade repair system, which has been applied in the Luo-Ro Company overhaul center. The maintenance range includes compressor tip and turbine blade sealing.

(2) US Pratt & Whitney Corporation

Following the development of laser cladding technology, Pratt & Whitney successfully established two automated laser cladding production lines, the first and second grade PWA1455 alloy rotors for JT8D and JT9D engines. A high-quality drill-base wear-resistant alloy layer is prepared on the blade serrated crown damping surface.

Pratt & Whitney has established a turbine blade laser welding machining center under the US Air Force project (IMIP program) to automate laser welding of components required for turbine blades, such as JTgD and Flo's secondary turbine rotor blades and V2500, F100 and PW2037 turbine guide vanes, etc.

(3) General Electric Company of the United States

General Electric (GE) first applied laser cladding technology to the repair of hot end components of gas turbines. It used a 5kW CO2 laser processing equipment in 1990 to repair the tip of the high pressure turbine blade. And claimed that the technology is one of the company's top ten new technologies.

GE successfully completed the laser welding assembly of the jet engine's baffles and guide vanes, effectively solving the laser welding deformation and cracking of the Inconel 600 and 700 series Hastelloy, Ren41 and Waspaloy brand nickel-based alloy small parts.

(4) Honeywell Corporation of the United States

In the field of advanced maintenance, Honeywell focuses on the following three areas: adaptive processing; laser welding, brazing and thermal processing; surface treatment and advanced coating processes. Among them, laser welding repair engine blade technology has been successfully used on the LF507 turbofan jet engine. According to statistics, the cost of refurbishing the blade is only one-fifth of the price of the new blade. For a commercial engine, repairing its low-jade turbine blades can save $180,000 over replacing the blades. The company has repaired 1 million blades of turbine blades and the restored blades have accumulated 20 million flight hours. Honeywell has dozens of patents on laser welding technology, including advanced powder feeding devices; 3-D ​​adaptive laser welding nozzles and gas fairings; and portable laser equipment.

Honeywell's equipment and technology are ISO 9001 certified and FAA/JAA certified for inspection, refurbishment and testing of engine components and accessories.

(5) German MTU Company

The German MTU company and the Hannover Laser Research Center have jointly developed laser surfacing technology for the hard surface coating or recovery geometry of the crown damping surface of the turbine blade.

MTU uses the Covered Laser Powder Cladding (CLPC) to repair the wear on the tip of the engine compressor blades. In the process of surfacing welding, the company used plasma arc welding (PAW), common laser cladding (LPC) and cladding welding for comparison test. The results show that in order to obtain a sufficient height of the deposition, the PAW and LPC technologies require 2 to 3 deposition processes, while the CLPC only needs to be performed once; the deposition rate of CLPC is significantly higher than the other two techniques; in the subsequent processing of the cladding PAW and LPC repaired the blade with a large amount of processing, while CLPC basically does not need to be processed. It can be considered that CLPC technology is a near net shape repair technology; the microhardness after repair shows that the hardness of CLPC and LPC processed materials is significantly higher than that of PAW, heat affected zone. Also much smaller than PAW. MTU uses efficient automated laser cladding technology to effectively reduce heat affected zone and reduce blade cracking. The first pass rate of the product can be stabilized above 95%, while the average pass rate of the traditional standard process (TIG surfacing) is less than 75%.

(6) American Wood Group Corporation

American Wood Group Company used laser powder alloy welding technology to repair aero-engine blades, and achieved good results. This repair technique can be used to repair single crystal and DS alloy parts that were previously considered unrepairable. Welds produced using this technology can accurately maintain the original shape and size of the part, reducing post-weld processing and increasing productivity.

(7) Canada Liburdi Group Corporation

The Liburdi Group of Canada has developed a patented blade repair technology that uses a combination of a laser and a solid metal wire. The basic process of this repair method is to let the laser beam melt the base of the workpiece to form a weld pool, then introduce the wire into the weld pool to melt it, and solidify the molten metal into a continuous weld by the relative movement of the base metal and the laser beam. . The advantage of this repair technique is that there is less heat input and therefore no complicated cooling system is required. Moreover, the speed is high and the solder joints can be "near-net" formed. The Liburdi Group has successfully applied the technology to the blade repair of the RB211 high-pressure turbine, medium-pressure turbine and low-pressure turbine of the Rolls-Royce company, and in 2001 was authorized by Luo Yiluo to specialize in RB211 engine blades and other related Laser welding repair of parts. The Liburdi Group also received GE, Siemens Westinghouse's "F"-level parts repair license for the GE7FA series of nozzles and combustion chambers. At the same time, it also undertakes the repair of the 1st, 2nd and 3rd grade blades of the Siemens V84.3A series.

Domestic application status

There are four kinds of wear-resistant treatment techniques for the surface of the aero-engine crown damping surface: one is plasma spraying like WP7; the other is vacuum high-temperature brazing wear-resistant alloy block like AII-31Φ; the third is like CFM56, using hydrogen Arc surfacing; Fourth, like the US JT8D, using laser cladding coating. The turbine blade sawtooth crown laser cladding technology developed by the Institute of Metals and the Shenyang Engine Research Institute (the deposited material is CoCrw with a small amount of rare earth elements) has been successfully used for the hardening of the canopy damping surface of two new aeroengines independently developed in China. On the surface coating strengthening treatment, a very satisfactory effect was obtained. Through a series of tests, including cladding process test, wear resistance test, oxidation and corrosion test, bonding test, hardness measurement and metallographic analysis, it is proved that the quality of laser cladding layer is much better than other traditional spraying processes.

The Institute of Metals of the Chinese Academy of Sciences uses laser calculus micro-welding technology to perform in-situ non-destructive repair of three-dimensional local damage (such as holes, pores, deep pits and cracks) of the workpiece, especially when the substrate is difficult to weld or non-weldable. To be effective. The advantage of laser micro-welding is that it can obtain the three-dimensional repair welding repair area with the smallest internal stress, the best combination of space interface and the least defects. This technology has been successfully applied to repair the casting process hole of the new machine hollow guide vane developed in China, and the loose and shrinkage holes on the blade mounting plate of the low-pressure turbine of the 1st, 2nd-level three-piece body without the amount of precision casting guide vane. Laser repair welding was performed on the defects such as cracks, and the test was carried out by the installed bench.

to sum up

Nowadays, the technology of using laser to repair key parts of the engine has been recognized by many engine manufacturers. Companies such as Luo Yiluo, Pratt & Whitney, and GE have introduced laser welding technology in their engine rebuild manuals. Therefore, it is foreseeable that the position of laser welding technology in engine overhaul will become more and more important.

U Bolt

U-BOLT: one classice fastener, is widely known and used. Main uses: construction installation, mechanical accessories connection, vehicles and ships, bridges, tunnels and railways, etc usually uesd together with nut.washe.

According to clients' demands, material can be Stainless Steel SS304/316/316L, Duplex Steel S32750/32760/2205/NAS660/904L..

The Standard is various, main standard is DIN/ANSI/GB, of course we also can accept JIS/BSW

Raw material should be cut in concrete length and processed by Cold/hot forge.surface finish,then can become various size fasteners.

Our Stainless Steel fasteners have great quality and are widely used in Heavy Industry.Shipping Industry.Construction Industry.Chemical Industry and Marine Industry.

U Bolt is one of our advantage Products. Chinese Manufacture, Qualified Hardware and Fasteners, Different size/Diameter/Tooth pitch, we all can satiafy your demands.

U Bolt,Custom U Bolts,Stainless U Bolts,Stainless Steel U Bolts

Taizhou Risco Stainless Steel Products Co.,Ltd , https://www.riscofastener.com