Product Code: ICA13_2002

Microstructure Control During Laser Deposition of Nickel-Based Superalloy Ds Rene80
Authors:
Heng Zhao, Institute of Laser Engineering, Beijing University of Technology; Beijing Peoples Republic of China
Dongyun Zhang, Beijing University of Technology; BeiJing USA
Zhibo Li, Institute of Laser Engineering, Beijing University of Technology; Beijing Peoples Republic of China
Xuanyang Cao, Institute of Laser Engineering, Beijing University of Technonogy; Beijing Peoples Republic of China
Tiechuan Zuo, Institute of Laser Engineering, Beijing University of Technology; Beijing Peoples Republic of China
Presented at ICALEO 2013

Rene 80 is a nickel-based superalloy strengthened by γ' phase precipitates. It has been widely used in aero-engine, gas turbines and other high temperature applications because of its pronounced combination of good corrosion resistance, fatigue resistance and excellent mechanical properties. A directionally solidified or single crystalline structure is desirable for high temperature application due to the absence of grain boundaries. Laser controlled directionally solidification is always considered to be the better way to manufacture and repair hot-section components.

The paper focused on the dendrite growing morphology control through comprehensive effect of laser deposition parameters and substrate crystallographic orientation. The deposition parameters, which have significant effect on grain morphology and orientation, were laser power, laser beam scanning velocity and powder feed rate. During solidification, substrate or previous deposited layer acts as heat sink, dendrites grow opposite to the heat flow direction, only when substrate crystallographic orientation is identical to the heat flow direction, it grow just along to the substrate crystallographic orientation. With same parameters elaborately selected, vertical walls were built up by familiar laser beam scanning pattern and different substrate crystallographic orientation, parallel and vertical to the building up direction of vertical wall, respectively.

The optical micrographs (OM) and Electron backscatter diffraction (EBSD) investigation were performed mainly on the longitudinal and vertical cross-section of both vertical walls above mentioned. The results showed that the vertical walls, built up by parallel to the substrate crystallographic orientation, have achieved full directionally solidified microstructure with fast identical crystallographic orientation, while vertical walls, built up by vertical to the substrate crystallographic orientation, have achieved 90°change in dendrite growth direction in subsequent layers resulted in zigzag-shaped grains. At the same time the pole figures gave the misorientation angle of the vertical wall with fast identical crystallographic orientation. γ' phase precipitates was investigated both of vertical walls by TEM image. The paper reported a route to produce full directionally solidified microstructure with different substrate crystallographic orientation.