The aviation industry is just one of many industries that may benefit from Nageswaran's research. It’s relevant wherever products are manufactured in superalloys such as Alloy 718. In addition to the combustion chambers of aircraft engines, the material is also used in industrial turbines for power generation.
The advantage of superalloys is that they retain their mechanical strength and hardness at extremely high temperatures and pressures. But at the same time, it’s a challenging material. When machining a superalloy, strong heat is generated which wear the tools down rapidly. Although the tool is cooled to minimize wear, it must be replaced often (in some cases every three minutes) – which costs both time and money.
Nageswaran has specifically studied how cooling can be improved when turning Alloy 718 with tools made of tungsten carbide. He has carried out a series of experiments where the turning is done with the aid of coolant applied at high pressures.
- The goal of my studies was to see if and how the tool life can be increased with the help of more efficient cooling and with new texture design on the tool's surfaces, explains Nageswaran.
- Cooling with cutting fluid under high-pressure on two sides of the tool increased the tool life by 12-25 percent. It also showed to be more efficient at low cutting speeds (45 m/min) rather than at high cutting speeds (90 m/min).
A new generation of tools
Nageswaran has also designed three different surface textures on tools manufactured at Sandvik Coromant and tested them in combination with high-pressure cooling.
- I have experimented with different textures on the tool surfaces and compared them to regular tools. All three textures resulted in less tool wear. The structure that gave the best results, Gen II, reduced wear by as much as 20-40 percent.
- Tool design is an interesting area to study further. A new European SMART Eureka research project “CRYOMACH” has started and is about cryogenic (liquid nitrogen) cooling. This project has a work package focused on how surface textures on tools with cryogenic coolant can contribute to an efficient cooling.
Two unexpected findings
During the experiments, Nageswaran made two new findings. The first one, was the existence of the Leidenfrost effect; when the coolant came in contact with the hot tool, an insulating layer was created, prohibiting the cooling effect. The second finding was the existence of “Cavitation”; a wear on the uncoated tungsten carbide tool, in form of pits on the tool surface occurring when using high-pressure cooling.
- It’s important to avoid these two effects in some way. If, for instance, the Leidenfrost effect occurs, you need to increase the coolant pressure or use textured tools to improve the tool life.
Fascinated by aircraft
It was the dream of becoming an astronaut or an airplane pilot that led Nageswaran onto the engineering trajectory.
- I have always been fascinated by aircraft and this profession became my way into the world of aviation. Researching in manufacturing processes for aviation engines is at least as interesting as working as a pilot.
After graduating with a bachelor’s degree in aeronautical engineering at Anna University Chennai in southern India, Nageswaran wanted to continue studying in England. But instead he decided to study at the Technical University of Madrid – a two-year master's degree in Aerospace Engineering.
- During my studies, I worked for a year and a half at the Rolls Royce-owned company ITP Aero in Madrid. But at the same time, the idea grew to go on with a doctoral program. When I saw the ad about University West's doctoral position with connection to the aviation industry, it was a perfect solution for me. I got the position and started at University West 2014.
Appreciating close cooperation with industry
Nageswaran's research project, “PROSAM”, is funded by Region Västra Götaland and has been carried out in close collaboration with GKN Aerospace in Trollhättan and Chalmers University of Technology in Gothenburg.
- A big advantage of researching at University West is that I can work so close to the aviation industry. At GKN Aerospace, I can see how the manufacturing process works in reality. Very few universities in the world have this type of close collaboration with industries.
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