Computational and experimental observations of welds in third-generation nickel-based superalloys

Abstract

The purpose of the present study is to introduce the weld quantitative solidification paths in the newly designed third-generation superalloys. The research has been conducted using both computational and experimental approaches. The model used the Scheil solidification relations to correlate the partitioning elements with their effects on the solidification paths. Accordingly, the k values were calculated for all the participating elements in the superalloy welds. The results of model demonstrated that these were very close to unity for austenite former elements, i.e. Ni, Co, Cr and Fe, while the other elements such as Ti, Nb and Mo displayed a significant tendency for segregation. The mathematical equations were calculated for weld solidification paths of superalloys. In all the welds, a remarkable segregation behaviour was observed, especially for Nb and Ti. The solidification path equations predicted type and amount of secondary phases. The solidification paths were compared with eutectic reactions , and , on the basis of the Ni–Ti–C and Ni–Nb–C ternary phase diagrams. Both the experimental measurements and microstructural observations of eutectics exhibited an appropriate accordance with the solidification paths obtained by model calculations.

Keywords:

• Computational
• solidification path
• superalloy
• weld

Acknowledgement

The author appreciates Professor Carlo Mapelli from the Dipartimento di Meccanica, Politecnico di Milano, Milano, Italy, for his facilities.