The Trends and Challenges of Metal AM in the Aerospace
The aerospace industry has always been strongly motivated to develop and implement innovative manufacturing technologies due to its high value-added product sector. The conventional manufacturing processes have been unable to meet the aviation industry's increasing demands for energy efficiency, pollution reduction, light weight, dependability, and comfort. How to manufacture high-performance with innovative design components is a big challenge in aerospace industry, however, metal additive manufacturing brings news possibilities and vitality to push up the development.
Market Trends of Additive Manufacturing in Aerospace
The rapid development of metal AM offers the possibility to meet these industry needs, as it offers unique advantages and feasibility to overcome limitations in geometry, materials, performance and functionality. It provides unprecedented design freedom for the fabrication of complex, composite and hybrid structures with high precision that is not possible with traditional manufacturing routes. The above-mentioned advantages of additive manufacturing are being applied in a wide range of industrial fields such as aerospace, automotive, electronics, medical, military, construction, etc. The global additive manufacturing market size has grown rapidly from about US$3 billion in 2013 to a market size of US$15.244 billion in 2021. According to Wohler's reports over the years, as the market size of the additive manufacturing industry continues to expand, the proportion of this technology in the aerospace industry is also growing rapidly. In the overall additive manufacturing market, the proportion of additive manufacturing scale in the aerospace industry will be 14.7%, 15.9% and 16.8% respectively in 2019-2021, and by 2021, it will reach 2.56 billion US dollars.
The advantages of additive manufacturing in Aerospace
Due to the following advantages of metal additive manufacturing, the applications in the aerospace industry is the significant segment of the entire market.
Freedom of geometric design
Materials can be transformed into free-form 3D components with complicated external shapes and interior geometry via metal AM. Additionally, it allows for the quick optimization of the production of lightweight components, which can attain equal or even better mechanical qualities through the use of lattice structures.
Customized and low-volume manufacturing
The expenses of high-volume production for metal AM are often greater than for conventional manufacturing procedures. However, the procedure is more cost-effective for low-volume specialized parts frequently encountered in the aerospace industry due to the high investment cost of mold fabrication, equipment, and inventory.
Functional integration and parts integration
Metal AM enables the production of integrated multifunctional parts with tailored material compositions, such as functionally graded materials. A functional multi-material combustor produced by an additive manufacturing process, by depositing a nickel-based superalloy on the surface of a copper alloy, simplifies traditional manufacturing processes while enhancing part functionality. Additionally, metal AM enables part integration, improving reliability and performance alongside functional integration. Complex aerospace components are traditionally assembled from multiple simple parts, which can reduce reliability and geometric accuracy, while increasing maintenance costs, compared to metal AM integrated components. Exzellenc had introduced that LAUNCHER company uses SLM technology to manufacture the world's largest single combustion chamber, providing the lowest propellant consumption and launch cost for small satellite launches. Combining multiple components into one can reduce costs and achieve high-performance regeneration Cooling design. In addition, the AMP laboratory at the University of Birmingham has also investigated the feasibility of using SLM technology to integrate thousands of engine components into several sections.
Shorten the production cycle
The whole product manufacturing cycle can be shortened due to the quicker manufacturing periods for producing components utilizing metal AM. Rolls-Royce reports that using laser additive manufacturing can save 30 percent in production time, while Boeing claims the reduction in the number of parts will reduce overall installation time by 50 percent. Liebherr Aerospace replaced traditional main flight high-pressure hydraulic valve block components with additively manufactured components, reducing weight by 35%, reducing the number of parts by 10 and reducing the required manufacturing time by more than 75%.
Less Materials and high energy efficiency
In terms of material utilization, SLM technology produces roughly 5% of material waste, which is significantly less than traditional subtractive manufacturing, which can produce up to 95% of material waste. Based on SLM technology, GE has created and produced gasoline nozzles that are lighter by 25%, use less fuel, and have a 30% higher cost-effectiveness. GE's laser additive manufacturing of burner and nozzle rings is a typical example of near-net-shape material savings, which would waste most of the material compared to traditional forged ingot machining. Additionally, using laser additive manufacturing to make aircraft components lighter is a particularly effective way to lower fuel usage. Reports state that every kilogram of weight eliminated in commercial aircraft can save around $3,000 in fuel annually and significantly cut carbon emissions.
Application scope and research status in Aerospace
Driven by the aforementioned advantages, the aerospace industry has been exploring the applications of additive manufacturing to produce aircraft parts, including various hinges, brackets, internal components, lightweight airframes, etc., and even engine components such as turbine blades with internal cooling channels, fuel nozzles and compressors, and integrated piping. Aero-engines are the heart of aircraft and the jewel in the crown of modern industry. The technology of metal AM is bound to promote the development of the entire aviation manufacturing industry.
Material distribution in the GE CF6 turbine engine for the Boeing 787 aircraft.
The most widely used high-value materials for aircraft engines mainly include steel, nickel-based superalloys and titanium alloys. Although the three materials have been extensively studied by the additive manufacturing academic community, but no comprehensive reviews of 3D printed high-strength steels, nor reviews of recent advances in titanium alloys and nickel-based superalloys. For example, recent reviews of nickel-based superalloys have focused only on In718, and there are significant research opportunities for newly developed nickel-based superalloys such as WSU 150 and single-crystal superalloys. There have been numerous investigations on Ti6Al4V, but a more thorough overview of the normal microstructure, static mechanical characteristics, and fatigue properties of this substance and other titanium alloys is still absent. Furthermore, some of the most critical issues in metal AM of titanium alloys, including how to achieve high ductility during printing and the formation mechanism of equiaxed β and α structures, are often not considered.
Therefore, a rigorous and dedicated review of the metal additive manufacturing of these specific high-performance alloys is required to summarize its progress and to identify research opportunities and gaps. Carryout more thorough research on the property map of aero-engine materials, including a detailed review of advanced high-strength steels, nickel-based superalloys, and titanium alloys, and draw the processing window, strength-ductility combination, fatigue performance of these three types of aero-engine materials. This will provide researchers with complete and up-to-date information on metal AM of key aero-engine materials, and encourage more inspiring scientific research in this field, which will hugely promote the wide applications of metal additive manufacturing in the aero-engine industry.