The aerospace industry started using additive manufacturing technology in the 1980s, and before that, additive manufacturing played only a minor role in the aerospace manufacturing industry to do rapid prototyping. The recent trend is that this technology will take a strategic position throughout the aerospace chain. Boeing, Airbus, Lockheed Martin, Honeywell, and Pratt & Whitney have all made exemplary moves.
The new generation of aircraft continues to high performance, high reliability, long life, low cost direction, more and more use of the overall structure, parts tend to be complex, large-scale, thus promoting the development and application of additive manufacturing technology. Additive manufacturing technology from the parts of the three-dimensional CAD model, without molds, direct manufacturing parts, can greatly reduce costs, shorten the development cycle, is to meet the modern aircraft rapid low-cost development of an important means, but also to meet the aerospace super-specification, complex metal structure manufacturing one of the key technologies.
Electron beam filament deposition molding
Electron beam filament deposition technology is also known as Electron Beam Freeform Fabrication (EBF3). In a vacuum environment, a high energy density electron beam bombards the metal surface to form a molten pool, the metal wire material is fed into the molten pool through the wire feeding device and melted, and at the same time the molten pool moves in accordance with the pre-programmed path, the metal material solidifies and accumulates layer by layer to form a dense metallurgical bond until a metal part or blank is manufactured.
Electron beam wire deposition rapid prototyping technology has some unique advantages, mainly in the following aspects:
(1) high deposition efficiency. E-beam can be easily realized in a number of 10kW high power output, can be in the higher power to achieve a very high deposition rate (15kg / h), for the formation of large metal structures, the e-beam wire deposition forming speed advantage is very obvious.
(2) Vacuum environment is conducive to the protection of parts. E-beam deposition forming in 10-3Pa vacuum bad environment, can effectively avoid the air harmful impurities (oxygen, nitrogen, hydrogen, etc.) in the high temperature state mixed into the metal parts, is very suitable for titanium, aluminum and other active metal processing.
(3) Good internal quality. E-beam is a "body" heat source, the melt pool is relatively deep, can eliminate the phenomenon of interlayer unfused; at the same time, the use of electron beam scanning of the melt pool rotary stirring, can significantly reduce the porosity and other defects. E-beam wire deposition molding of titanium alloy parts, the internal quality of ultrasonic flaw detection can reach AA level.
(4) Multifunctional processing can be realized. Electron beam output power can be adjusted in a wide range, and can be realized through the electromagnetic field of the beam movement mode and focusing flexible control, can realize high-frequency complex scanning movement. The use of surface scanning technology, can realize a large area of preheating and slow cooling, the use of multi-beam beam processing technology, can realize the multi-beam streams work at the same time, in the same equipment, can realize the fusion wire deposition molding, but also can realize the deep fusion welding. The use of electron beam multifunctional processing technology, according to the structural form of the parts as well as the performance requirements of the service, to take a variety of processing technology combinations, to achieve a variety of process synergies to optimize the design and manufacture, in order to achieve the optimization of cost-effectiveness.
The Massachusetts Institute of Technology's V.R. Dave and others first proposed the technology and trial production of Inconel 718 alloy turbine disk. 2002, NASA Langley Research Center's K.M. Taminger and others proposed the EBF3 technology, focusing on micro-gravity conditions under the molding technology research. During the same period, with the support of the Navy, Air Force, Department of Defense and other institutions, the U.S. company Sciaky, Lockheed Martin, Boeing and other companies also cooperated in the same period of time to carry out research, mainly dedicated to the manufacture of large aerospace metal parts. When forming titanium alloys, the maximum forming speed of up to 18kg / h, mechanical properties to meet the requirements of the AMS4999 standard. Lockheed Martin selected F-35 aircraft flap aileron beam ready to use the electron beam deposition molding instead of forging, is expected to reduce the cost of parts by 30% to 60%. According to reports, the F-35 aircraft equipped with electron beam deposition molding titanium alloy parts have been test-flown in early 2013. 2007 U.S. CTC led a comprehensive team for the Navy's unmanned combat aircraft program, the development of the "unmanned combat aircraft metal manufacturing technology to enhance the program" (N-UCASMetallic Manufacturing Technology Transition Program), and the UCASMetallic Manufacturing Technology Transition Program. Manufacturing Technology Transition Program), selected electron beam wire deposition molding technology as the future of large-scale structure cost-effective manufacturing program. The goal is to reduce the weight and cost of UAV metal structures by 35 percent.
Photo: Parts made by Sciaky
The AVIC Beijing Aeronautical Manufacturing Engineering Research Institute began research work on electron beam fused filament deposition molding technology in 2006, and developed electron beam fused filament deposition molding equipment. Developed the largest electron beam forming equipment vacuum chamber 46m3, effective processing range of 1.5m × 0.8m × 3m, 5-axis linkage, dual-channel wire feeding. On this basis, the mechanical properties of titanium alloys such as TC4, TA15, TC11, TC18 and TC21 as well as A100 ultra-high-strength steel have been studied, and a large number of titanium alloy parts and test pieces have been developed.In 2012, titanium alloy parts manufactured by electron beam wire forming were the first to realize the mounting application on the structure of domestic aircraft.
Photo: E-beam fused-wire deposition molding equipment at AVIC's Beijing Aeronautical Manufacturing Engineering Research
Laser direct deposition additive molding
Laser direct deposition technology is a kind of advanced manufacturing technology developed on the basis of rapid prototyping and laser cladding technology. This technology is based on the principle of discrete/stacking, through the three-dimensional CAD model of the parts of the layered processing, to obtain the two-dimensional contour information of the cross-section of each layer and generate the processing path, in an inert gas-protected environment, the high energy density of the laser as a heat source, according to the predetermined processing path, the simultaneous delivery of powder or wire material layer by layer melting and stacking, so as to achieve the direct manufacturing and repair of metal parts.
The characteristics of laser direct deposition technology are as follows: (1) no need for molds; (2) suitable for difficult-to-machine metal materials preparation; (3) high precision, can achieve complex parts near net forming; (4) internal organization fine and uniform, excellent mechanical properties; (5) can be prepared for the gradient material; (6) can be achieved by rapid repair of the damaged parts; (7) processing flexibility is high, and can be realized in multi-species, variable batch Rapid conversion of parts manufacturing.
In China, the LSF equipment of Xi'an Platinum Lite is a representative of this type of technology. In addition, the typical enterprise and the United States OPTOMEC company, France BeAM company, Germany through the fast as well as CNC machine tool companies specializing in the provision of additive manufacturing package HYBRID company.
Laser direct deposition technology was first developed in the 1990s in the U.S. In 1995, Sandia National Laboratories in the U.S. developed rapid near-net-shaping technology that melts metal powder layer by layer directly from a laser beam to create dense metal parts. Since then, Sandia National Laboratory has carried out a large number of forming process studies using LENS technology for a variety of metal materials such as nickel-based high temperature alloys, titanium alloys, austenitic stainless steels, tool steels, tungsten, etc. In 1997, Optomec Design was licensed to commercialize the LENS technology, and introduced laser direct deposition equipment. 1995, the U.S. Department of Defense Advanced Research Projects Agency and the Naval Institute jointly developed the laser beam to produce dense metal parts. Advanced Research Projects Agency and the Naval Institute jointly funded by the Johns Hopkins University, Pennsylvania State University and MTS Corporation **** with the development of a titanium alloy titanium alloys called "flexible manufacturing technology" project, the goal is to use high-power CO2 lasers to achieve the manufacture of large-size titanium alloy parts. Based on the results of this project, MTS funded the formation of AeroMet in 1997 in collaboration with Johns Hopkins University and Penn State University. In order to improve the deposition efficiency and production of large titanium alloy parts, AeroMet company using 14 ~ 18kW high-power CO2 laser and 3.0m × 3.0m × 1.2m large processing chamber, Ti-6Al-4V alloy deposition rate up to 1 ~ 2kg / h. AeroMet company has obtained the U.S. military and the three major U.S. military aircraft manufacturers Boeing, Lockheed Martin, AeroMet has been funded by the U.S. military and three major U.S. military aircraft manufacturers Boeing, Lockheed Martin, Grumman, to carry out research on laser direct deposition of titanium alloy structural parts of the aircraft fuselage, and has successively completed the laser direct deposition of titanium alloy structural parts of the performance assessment and development of technical standards, and was the first to realize the direct deposition of laser Ti-6Al-4V titanium alloy sub-bearing components in the world in 2002, such as the installation of the application of the aircraft F / A-18.
Since the "Tenth Five-Year Plan", under the financial support of the National Natural Science Foundation of China, the National 863 Program, the National 973 Program, the General Armament Pre-Research Program and other major national scientific and technological research programs, Beijing University of Aeronautics and Astronautics, Northwestern Polytechnical University, the AVIC Beijing Aviation Manufacturing Engineering Research Institute and other domestic research institutions have carried out research on the laser direct deposition process. Laser direct deposition process research, mechanical properties control, complete sets of equipment research and development and engineering applications of key technology research, and has made greater progress.
Titanium alloy upper and lower wing edge strips, which are the key parts in the wing-body assembly of C919, are manufactured by Xi'an Platinum Laser Forming Technology Co., Ltd. by using metal additive manufacturing technology (3D printing), and the left upper edge strip with the maximum size of 3070mm and the maximum weight of 196kg in the upper and lower wing edge strips is completed and delivered within 25 days, which has greatly shortened the development cycle of the key parts of aviation and achieved the goal of realizing the core aeronautics and aviation technology.
This is a new breakthrough in core aviation manufacturing technology.