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Materials Frontier No.162

Title: On Solving Weldability Problem of Advanced Nickel-base Superalloys
Speaker: Professor Olanrewaju A. Ojo, Ph.D., P.Eng.
Date/Time: 2015-04-21,10:00
Venue: Room.304, Material Building E
Inviter: Dr. Pulin NIE
Professor Olanrewaju Ojo was born in 1974 in Nigeria. He graduated with a First Class Honors BSc degree from Obafemi Awolowo University, Ile-Ife, Nigeria in 1997. He subsequently obtained his MSc and PhD from the University of Manitoba, Winnipeg, Canada in 2002 and 2005, respectively, with a prestigious award of University of Manitoba Distinguished PhD Dissertation Award for ground-breaking novel academic contributions. He received the highly covetable NSERC post-doctoral research fellowship from the Government of Canada and worked as a post-doctoral research fellow at the University of Manitoba and Ecole Polytechnique in Canada in 2005. In January 2006, he started as a tenure-track Assistant Professor at the University of Manitoba and he received early promotion to Associate Professor, early tenure and early promotion to Full Professor in 2009, 2011 and 2013, respectively.
Professor Ojo is an internationally recognised expert in the field of joining of advanced aerospace materials. He has over 120 international journal publications and international conference papers and presentations. Out of these, more than 85 papers are in refereed international archival journal publications. One of his papers won the Award of the Best Paper out of all the papers published in the Canadian Metallurgical Quarterly in 2007 and one of his research work received the 2009 Microscopical Society of Canada Gerard T. Simon Award for the Best Presentation. Professor Ojo was awarded 2013 Rh Award for outstanding contributions to research and scholarship and he was also nominated by the University of Manitoba for the Canadian prestigious 2014 Steacie Prize award. In 2014, he received the Excellence in Engineering Teaching award. Professor Ojo currently serves as a reviewer of research papers submitted for publication in several top tier refereed international Materials journals and he was nominated as an Executive Editor of the Journal of Aeronautics and Aerospace Engineering. He has supervised more than 36 research students including PhD and postdoctoral research fellows. His expertise is widely sought after by various international aerospace companies including Pratt and Whitney Canada, Standard Aero Ltd, Magellan Aerospace and since 2014 he has been a yearly research visitor to the GKN Aerospace in Sweden, formerly known as Volvo Aerospace.

To meet the ever-increasing demand for higher operating temperatures for improved efficiency of gas turbine engines and lower greenhouse emission, advanced alloy designs have been utilized to produce heat resistant nickel-base superalloys with remarkable high temperature properties. Nevertheless, the development that has occurred in advanced superalloys in the past two decades has not been matched by improvement in joining techniques for these materials. Welding is not only an essential economical and efficient joining technique in the manufacturing of gas turbines including aero-engines, but also vital for the repair and overhaul of service degraded turbine and aero-engine parts. Laser beam welding has become an attractive joining process to rapidly produce deep and narrow low heat input welds with higher reliability and productivity compared to the widely used arc welding process. Unfortunately, the application of welding, including laser welding, to the joining of high strength precipitation hardened nickel-base superalloys is currently severely restricted due to high susceptibility of these materials to cracking during welding and post-weld heat treatment. This becomes even more challenging due to the fact that some of the constituents of superalloys added to improve their properties are ironically promoting their propensity to weld cracking. The weldabilitiy problem, its causes and possible measures to alleviate or prevent its occurrence will be presented and discussed.

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