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Effect of grain boundary characteristics on hot tearing in directional solidification of superalloys

Published online by Cambridge University Press:  03 March 2011

Yizhou Zhou ,
Andreas Volek  and
Robert F. Singer
Yizhou Zhou
Affiliation:
WTM Institute, Department of Materials Science, University of Erlangen–Nürnberg, 91058 Erlangen, Germany
Andreas Volek
Affiliation:
WTM Institute, Department of Materials Science, University of Erlangen–Nürnberg, 91058 Erlangen, Germany
Robert F. Singer*
Affiliation:
WTM Institute, Department of Materials Science, University of Erlangen–Nürnberg, 91058 Erlangen, Germany
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

The effect of grain boundary (GB) misorientation on hot tearing susceptibility of directionally solidified (DS) nickel-based superalloys was explored. We found that the castability of second generation nickel-based superalloy CMSX-4 is inferior to DS superalloy IN792, an alloy well known for bad castability. The castability of CMSX-4 is somewhat improved at a higher solidification rate. The hot tearing tendency increases with increasing GB misorientation angle. As feeding tendency becomes greater with increasing misorientation, this points to the importance of GB cohesion for solidification cracking in the alloy. Microstructure investigation reveals that hot tearing is associated with formation of continuous gamma and gamma prime eutectic films at the GB in CMSX-4. We assume that the gamma and gamma prime eutectic, which reflects the remaining liquid at the end of solidification, prevents the impinging dendrite arms from touching and in this way decreases cohesion.

Keywords

DefectsDirectional solidificationGrain boundaries
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 9 , September 2006 , pp. 2361 - 2370
Copyright
Copyright © Materials Research Society 2006

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