Thermal Efficient High Temperature Resistant Light Weight Metal (γ-TiAl), a Potential Material for Aviation Application.

World’s leading aviation industries predict that due to globalization as well as growth in the per capita income the use of airplanes will increase rapidly in years to come. Advisory Council for Aviation Research and Innovation reported that, the aeronautical industries by year 2050 have to meet the stringent quality standards with respect to (i) high fuel efficiency (ii) controlled emission of CO2, NO2 and (iii) noise pollution as compared to standards of year 2000 [ACARE Aviation in Europe 2014: A vision for 2050 ].
Enhancements in propulsive efficiency or thermal efficiency are the two main criteria that govern the above quality standards. Propulsive efficiency of aircraft can be improved by providing higher by pass ratio with the geared turbo fans. The limitation of small ground clearance needs to be modified in order to enhance the propulsive efficiency effectively. This may not be cost effective owing to redesigning the structure. However, thermal efficiency may be improved by adopting:
  1. Advanced materials i.e. High Temperature Resistant Light Weight Metals (HTRLWM) e.g. single crystal, metal matrix composite (MMC), polymer matrix composite (PMC) and ceramic matrix composite (CMC),
  2.  Efficient cooling holes design (tabulated holes) and
  3.       Methods of thermal envelop.


Light weight metal, Gamma Titanium Aluminide (γ-TiAl) found to be a prominent material for low pressure turbine blade that can replace the twice dense Inconel super alloy and improve the operating thermal efficiency [D. Baehre, A. Ernst, K. Weißhaar, H. Natter, M. Stolpe, R. Busch], Procedia, CIRP 42, 2016, pp.137–142.
Machining of this material using traditional methods is restricted due to high mechanical strength. Also thermal and mechanical stresses induced during machining leads to damage the surface. Advanced manufacturing process such as Electrochemical Machining (ECM) offers a better alternative without any defect and damage [A. V. Kulkarni, D. S. Bilgi, V. K. Jain] ICRIET ISBN-978-93-5346-940-5, 2019, pp. 771-774.
ECM works on the principle of Faradays law of electrolysis where, material is being removed atom by atom. The machining is independent of hardness. It is reported that there is negligible tool wear and stress free machined surface produced.
Need of the present is to establish process capability of anodic dissolution of γ-TiAl using different ECM electrolytes, inter electrode gap dynamics, cathode tool design and mode of  power supply, selection of appropriate hybrid process etc. Investigation towards process capability of high temperature resistant light weight metals and replacing Inconel with γ-TiAl may lead to significant weight reduction (~ 30%) of airplane.

Prof. Dr. D.S.Bilgi
Department of Mechanical Engineering TSSM's Bhivarabai Sawant College of Engineering and Research, 
Narhe, Pune.
Email: dsbilgi@yahoo.com

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