additive manufacturing technology has been used in aviation industry since 198s. Previously, additive manufacturing only played a small role in rapid prototyping in aviation manufacturing. The recent development trend is that this technology will occupy a strategic position in the entire aerospace industry chain. Including Boeing, Airbus, Lockheed Martin, Honeywell and Pratt & Whitney, all set an example.
The new generation of aircraft is developing in the direction of high performance, high reliability, long life and low cost, and more and more integral structures are adopted, and the parts tend to be complicated and large, thus promoting the development and application of additive manufacturing technology. Additive manufacturing technology starts from the three-dimensional CAD model of parts, and directly manufactures parts without molds, which can greatly reduce the cost and shorten the development cycle. It is an important means to meet the rapid and low-cost development of modern aircraft, and it is also one of the key technologies to meet the requirements of aerospace over-specification and complex metal structure manufacturing.
electron beam fuse deposition forming
electron beam fuse deposition technology is also called electron beam free form manufacturing (EBF3). In a vacuum environment, electron beams with high energy density bombard the metal surface to form a molten pool, and the metal wire is fed into the molten pool through a wire feeding device and melted. At the same time, the molten pool moves according to a pre-planned path, and the metal materials are solidified and accumulated layer by layer to form a dense metallurgical bond until a metal part or blank is manufactured.
The rapid prototyping technology of electron beam fuse deposition has some unique advantages, mainly in the following aspects:
(1) High deposition efficiency. Electron beam can easily achieve a high power output of tens of 1kW, and can achieve a high deposition rate (15kg/h) at a higher power. For the formation of large metal structures, the deposition speed advantage of electron beam fuse is very obvious.
(2) vacuum environment is beneficial to the protection of parts. Electron beam fuse deposition is carried out in 1-3Pa vacuum environment, which can effectively avoid harmful impurities (oxygen, nitrogen, hydrogen, etc.) in the air from mixing with metal parts at high temperature, and is very suitable for processing active metals such as titanium and aluminum.
(3) good internal quality. Electron beam is a "bulk" heat source, and the molten pool is relatively deep, which can eliminate the phenomenon of interlayer unfusion; At the same time, the defects such as blowholes can be obviously reduced by rotating and stirring the molten pool with electron beam scanning. The internal quality of titanium alloy parts formed by electron beam fuse deposition can reach AA level by ultrasonic flaw detection.
(4) multifunctional machining can be realized. The output power of electron beam can be adjusted in a wide range, and the flexible control of beam movement and focusing can be realized through electromagnetic field, which can realize high-frequency complex scanning movement. Using surface scanning technology, large-area preheating and slow cooling can be realized, and using multi-beam splitting processing technology, multiple beams can work at the same time. On the same equipment, both fuse deposition and deep penetration welding can be realized. Using the multifunctional processing technology of electron beam, we can adopt a variety of processing technology combinations according to the structural form of parts and the requirements of service performance, and realize the collaborative optimization design and manufacturing of multiple processes to achieve the optimization of cost-effectiveness.
V.R.Dave of Massachusetts Institute of Technology and others first put forward this technology and trial-produced Inconel 718 alloy turbine disk. In 22, K.M. Taminger of the Langley Research Center of the National Aeronautics and Space Administration (NASA) and others put forward EBF3 technology, focusing on the research of forming technology under microgravity conditions. In the same period, with the support of the navy, air force, Ministry of National Defense and other institutions, Sciaky Company of the United States, Lockheed Martin and Boeing Company also cooperated in the same period to carry out research, mainly devoted to the manufacture of large aviation metal parts. When forming titanium alloy, the maximum forming speed can reach 18kg/h, and the mechanical properties meet the requirements of AMS4999 standard. Lockheed Martin Company has selected the aileron beam of F-35 aircraft to replace forging with electron beam fuse deposition, and it is expected that the cost of parts will be reduced by 3%~6%. It is reported that the F-35 aircraft equipped with titanium alloy parts formed by electron beam fuse deposition was tested in early 213. In 27, CTC Company of the United States led a comprehensive team to formulate the "N-UCAS Metal Manufacturing Technology Transition Program" for the Navy's unmanned combat aircraft plan, and selected the electron beam fuse deposition technology as a low-cost and efficient manufacturing scheme for large-scale structures in the future. The goal is to reduce the weight and cost of UAV metal structure by 35%.
picture: parts manufactured by Sciaky
avic Beijing aviation manufacturing engineering research institute started the research work of electron beam fuse deposition forming technology in 26, and developed the electron beam fuse deposition forming equipment. The largest electron beam forming equipment developed has a vacuum chamber of 46m3, with an effective processing range of 1.5m×.8m×3m, 5-axis linkage and double-channel wire feeding. On this basis, the mechanical properties of TC4, TA15, TC11, TC18, TC21 and A1 ultra-high strength steel were studied, and a large number of titanium alloy parts and test pieces were developed. In 212, titanium alloy parts manufactured by electron beam fuse forming were the first to be installed in domestic aircraft structures.
Photo: Electron beam fuse deposition forming equipment researched by AVIC Beijing Aviation Manufacturing Engineering
Laser direct deposition additive forming
Laser direct deposition technology is an advanced manufacturing technology developed on the basis of rapid prototyping technology and laser cladding technology. Based on the discrete/stacking principle, this technology obtains the two-dimensional contour information of each layer's cross-section by layering the three-dimensional CAD model of the part, and generates the machining path. In the inert gas protection environment, the laser with high energy density is used as the heat source, and the synchronously fed powder or wire is melted and stacked layer by layer according to the predetermined machining path, so as to realize the direct manufacture and repair of metal parts.
The characteristics of laser direct deposition technology are as follows: (1) No mold is needed; (2) it is suitable for the preparation of difficult-to-machine metal materials; (3) The precision is high, and the near-net forming of complex parts can be realized; (4) Fine and uniform internal structure and excellent mechanical properties; (5) gradient materials can be prepared; (6) The damaged parts can be quickly repaired; (7) The machining flexibility is high, and the rapid conversion of multi-variety and variable batch parts manufacturing can be realized.
In China, LSF equipment of Xi 'an Platinum is the representative of this kind of technology. In addition, typical enterprises include OPTOMEC Company in the United States, BeAM Company in France, Trumpf Company in Germany and HYBRID Company which provides additive manufacturing packages for CNC machine tools companies.
laser direct deposition technology was first developed from America in 199s. In 1995, Sandia National Laboratory of the United States developed a rapid near-net-shape forming technology to manufacture dense metal parts by melting metal powder layer by layer directly by laser beam. Since then, Sandia National Laboratory has carried out a lot of research on the forming process of nickel-based superalloy, titanium alloy, austenitic stainless steel, tool steel, tungsten and other metal materials by using LENS technology. In 1997, Optomec Design Company obtained the commercialization license of LENS technology and introduced a complete set of laser direct deposition equipment. In 1995, the Advanced Research Projects Agency of the US Department of Defense and the Naval Research Institute jointly funded a project called "Flexible Manufacturing Technology of Titanium Alloys", which was jointly developed by Johns Hopkins University, Penn State University and MTS Company. The goal was to manufacture large-size titanium alloy parts by using high-power CO2 laser. Based on the research results of this project, in 1997, MTS Company established AeroMet Company in cooperation with Johns Hopkins University and Penn State University. In order to improve the deposition efficiency and produce large titanium alloy parts, AeroMet Company adopted 14~18kW high-power CO2 laser and 3.m×3.m×1.2m large processing chamber, and the deposition rate of Ti-6Al-4V alloy reached 1 ~ 2kg/h.. AeroMet Company was funded by the US military and Boeing, Lockheed Martin and Grumman, the three major US military aircraft manufacturers, and carried out the research on laser direct deposition technology of titanium alloy structural parts of aircraft fuselage, successively completed the performance assessment and technical standard formulation of laser direct deposition titanium alloy structural parts, and in 22, it took the lead in the world to realize the installation and application of laser direct deposition Ti-6Al-4V titanium alloy secondary bearing components on F/A-18 and other aircraft.
Since the Tenth Five-Year Plan, with the support of the National Natural Science Foundation of China, the National 863 Plan, the National 973 Plan, and the pre-research plan for final assembly, many domestic research institutions, such as Beihang University, Northwestern Polytechnical University, and AVIC Beijing Aviation Manufacturing Engineering Research Institute, have carried out research on laser direct deposition technology, mechanical property control, complete equipment research and development, and key technologies for engineering application, and made great progress.
the upper and lower flange strips of titanium alloy, which are the key components in most sections of p>C919 passenger wing body assembly, were manufactured by Xi 'an Platinum Laser Forming Technology Co., Ltd. by using the metal additive manufacturing technology (3D printing). The left upper flange strip with the largest size of 37mm and the largest weight of 196kg in the upper and lower flange strips was delivered in only 25 days, which greatly shortened the research and development cycle of aviation key components and realized the last manufacturing technology of aviation core.