Baohua Chang
Baohua Chang, Ph.D
Professor
State Key Laboratory of Tribology, Department of Mechanical Engineering,
Tsinghua University, P. R. China
bhchang@tsinghua.edu.cn
Biography:
Dr. Baohua Chang is currently an associate professor at the Department of Mechanical Engineering, Tsinghua University. He obtained his bachelor’s degree and PhD from Xi’an Jiaotong University, carried out post-doctoral research at University of Waterloo, Canada, and he worked at TWI Ltd, UK as a Marie Curie Fellow (IIF) of European Union. Dr. Chang acts as a committee member for high-energy beams and special welding processes in China Welding Society, and an associate editor of the international journal Transactions on Intelligent Welding Manufacturing. His research focuses mainly on the numerical modeling and quality control of advanced materials processing technologies (mainly welding and additive manufacturing). He has published more than 100 papers, been granted 8 invention patents, and coauthored 2 books.
Abstract:
Influences of cooling conditions in laser metal deposition of a di-rectionally-solidified superalloy
Directionally solidified nickel-based superalloys are widely used in manufacturing turbine blades, which may fail due to cracking and material loss during service. Laser metal deposition has been considered as a promising technology in repairing the dam-aged components thanks to its high temperature gradient that is conducive to the growth of directional microstructure. In this paper, the influences of cooling condi-tions (natural and forced cooling) on the microstructure development and liquation cracks were studied for the laser deposition of a directionally solidified superalloy IC10. Experimental results showed that compared to the natural cooling, the height of columnar crystals in the deposits was significantly increased, and the liquation cracks in base metal were reduced under the forced cooling condition. The effects of cooling conditions on temperature and stress fields were analyzed through a thermo-elastoplastic finite element analysis. It was revealed that the ratio of temperature gra-dient to solidification rate (G/v) in the growth direction of the columnar crystals was notably increased by employing the forced cooling condition. Meanwhile, the maxi-mum tensile stress and high tensile stress region in the substrates were reduced. The numerical findings explained the experimental observation quite well.
Figure 1. Cross sections of laser deposits formed under two cooling conditions
Professor
State Key Laboratory of Tribology, Department of Mechanical Engineering,
Tsinghua University, P. R. China
bhchang@tsinghua.edu.cn
Biography:
Dr. Baohua Chang is currently an associate professor at the Department of Mechanical Engineering, Tsinghua University. He obtained his bachelor’s degree and PhD from Xi’an Jiaotong University, carried out post-doctoral research at University of Waterloo, Canada, and he worked at TWI Ltd, UK as a Marie Curie Fellow (IIF) of European Union. Dr. Chang acts as a committee member for high-energy beams and special welding processes in China Welding Society, and an associate editor of the international journal Transactions on Intelligent Welding Manufacturing. His research focuses mainly on the numerical modeling and quality control of advanced materials processing technologies (mainly welding and additive manufacturing). He has published more than 100 papers, been granted 8 invention patents, and coauthored 2 books.
Abstract:
Influences of cooling conditions in laser metal deposition of a di-rectionally-solidified superalloy
Directionally solidified nickel-based superalloys are widely used in manufacturing turbine blades, which may fail due to cracking and material loss during service. Laser metal deposition has been considered as a promising technology in repairing the dam-aged components thanks to its high temperature gradient that is conducive to the growth of directional microstructure. In this paper, the influences of cooling condi-tions (natural and forced cooling) on the microstructure development and liquation cracks were studied for the laser deposition of a directionally solidified superalloy IC10. Experimental results showed that compared to the natural cooling, the height of columnar crystals in the deposits was significantly increased, and the liquation cracks in base metal were reduced under the forced cooling condition. The effects of cooling conditions on temperature and stress fields were analyzed through a thermo-elastoplastic finite element analysis. It was revealed that the ratio of temperature gra-dient to solidification rate (G/v) in the growth direction of the columnar crystals was notably increased by employing the forced cooling condition. Meanwhile, the maxi-mum tensile stress and high tensile stress region in the substrates were reduced. The numerical findings explained the experimental observation quite well.