In-Situ Monitoring and Control During Laser Powder Bed Fusion of Nickel Superalloys

Additive Manufacturing technologies present a pathway to the production of components with uniform properties independent of their geometry. Currently, one of the main barriers to the wider adoption of this family of technologies by industry is the reliability with which components can be printed, particularly with complex alloys that do not lend themselves to processing in this fashion. CM247-LC is an alloy of great interest for its outstanding strength and resistance to deformation at elevated temperatures. This alloy is classed as difficult-to-weld because of its high content of the nickel gamma-prime phase, a key component of its high-strength properties. A series of different experimental methods has been explored in this study to address the predisposition of the alloy to crack on production during the Laser Powder Bed Fusion (LPBF) process. Response-surface methodology has been applied to determine a suitable processing window for the alloy through the altering of laser parameters, using the temperature reading of in-situ sensors to examine the behavior of the material during the process. In addition, the use of a pre-heated build substrate for LPBF has shown a significant improvement in the consistency of the material, demonstrating the effectiveness of controlling the temperature of the powder bed. Automatic control techniques for LPBF have also been explored, utilizing an advanced neural network to make changes to the laser processing parameters in real-time. This automatic control is demonstrated in this work, showing the power of live process control for the consistent property and microstructural control of nickel superalloys. Further development of in-situ monitoring methods and techniques is also presented, with both co-axial and off-axis techniques providing valuable insights into how CM247-LC behaves during the LPBF process and how these monitoring methods may be integrated into an automatic control system.