Analysis of the Future of Difficult-to-machine Materials in Aviation Manufacturing

It is predicted that titanium alloys are increasingly used in structural parts, landing gear and other hardware equipment. The use of composite materials (mainly CFRP) in aircraft is also becoming more common. They have a high strength-to-weight ratio, good corrosion resistance and low thermal expansion; their properties can be adjusted to suit specific applications. CFRP is widely used in wing main beams, wing and fuselage skins. The composite material consists of fibers taken from a plastic matrix. These fibers can also be used for fabric styling without any substrate. The main structure of the 50% Boeing 787 Dreamliner (including the fuselage and wings) is made of composite materials.

The development of aircraft design goes hand in hand with the development of new materials. As a result, the current aircraft can fly farther and faster and have a higher payload. At the same time, aircraft use less fuel, which means less pollutant emissions and lower costs.

There are three types of hard-to-machine materials that can be used to make hardware such as fuselage, wings, and landing gear and aircraft engines. They are superalloys, titanium alloys and composites. The latter includes new carbon fiber reinforced plastics (CFRP) and newer glass fiber reinforced plastics (GRP). In general, CFRP and GRP have been laminated or their surfaces have been metallized (such as aluminum alloys). All of these monolithic materials and laminates are difficult to process. As the engine temperature increases, the engine efficiency increases accordingly. The temperature of the heating area of ​​the jet engine is higher than ever before, and superalloys (mainly nickel-base and cobalt-base alloys) still maintain excellent mechanical and chemical properties. Compared to steel components, superalloy parts are smaller in size and lighter in weight. Every kilogram reduction in engine weight means that the cost of fuel can be reduced by $150,000 while the engine is in service. Superalloys account for about 50% of the total weight of new engines. Titanium alloys provide extremely high strength to weight ratios and excellent corrosion resistance. Their strength is comparable to that of steel, but their weight is only 40% of that of steel; their strength is twice that of aluminum alloys, but their weight is only 60% higher than that of aluminum. Since the 1950s, the supply of light alloys on the market has clearly failed to meet the increasingly difficult requirements of airframe and engine parts, which has made the importance of titanium alloys increasingly prominent.

Why are these materials so difficult to process? The high temperature strength of superalloys and titanium alloys means that with high hardness and stiffness at the cutting temperature, a greater cutting force is generated on the cutting edge of the tool, resulting in a micro-collapse and deformation of the cutting edge. During bending (during swarf formation) and due to poor thermal conductivity, these metals generate more heat and thus the cutting temperature reaches a very high level. As the material's high temperature strength, toughness, and ductility increase, chip breaking becomes more difficult. Processing heat-treating alloys often produces abrasive grains that wear the cutting edges, and can also cause the workpiece surface to harden, making it difficult to maintain close tolerances. The metallographic integrity of the surface of the part will be damaged during the processing and reduce the fatigue strength. The carbon fiber in the composite material has good toughness, resulting in rapid dulling of the cutting edge. Improper use of the cutting speed can cause exfoliation and micro-disintegration of workpieces and the formation of burrs. Hole machining can cause delamination of high resin content common composites and cracking of high fiber content composites. For laminated (laminated) composites, metal chips that splatter out during the drilling process can damage the surface of such composites.

What will happen in the future? Intense market competition has forced designers to look for lighter, more rugged, heat-resistant and corrosion-resistant materials that will allow aircraft to meet increasingly stringent requirements. Metallurgists, chemists, and plastic engineers are dedicated to developing materials that meet future needs. On the negative side, it is almost certain that materials that have improved their physical and chemical properties are more difficult to process, but this is exactly the challenge Secoo is going to tackle.

Seco offers a range of advanced tool solutions for efficient, high-precision milling, turning, cutting and drilling of aerospace materials.

JabroTM milling cutters with CVD diamond coating reduce wear, specializes in composites such as multilayered carbon fibres and glass fibres, and burr-free (top and bottom) processing of high-performance industrial plastics such as PEEK and honeycombs , side milling, 3D copy milling, milling contouring and milling operations.

For processing Inconel and other high-temperature alloys, SecomaxTM PCBN tools have the same service life as tungsten carbide materials, but their cutting speed is 10 times faster, which leads to increased cutting length. Secomax CBN170 is a new grade of material in which whisker ceramic binders have unequalled cutting edge strength for this application. In order to expand the SecoFeedmaxTM drill bit series used in China's metalworking online copyrighted titanium alloys and high-temperature alloys (T and M groove types, respectively), Seco has introduced a series of new solid carbide drill bits with CVD diamond coating for CFRP. Material for hole machining. Thanks to its specially developed drill tip geometry, high-quality, non-delaminating holes can be drilled, while the diamond coating also extends tool life and productivity. This drill series includes conventional (single diameter) drills and chamfered drills (integrated drills).