Blue Laser Directed Energy Deposition of a CuCrZr Alloy: Effect of Process Parameters on the microstructure

CuCrZr is a commercial high-performance copper alloy valued for its combination of excellent thermal and electrical conductivity, corrosion resistance and working temperature resistance up to 400°C. This makes it suitable for key applications in aerospace, automotive or energy. However, laser-based additive manufacturing of copper alloys remains challenging due to their high reflectivity and thermal conductivity, which may result in poor laser absorption, unstable melt pool behavior as well as difficulties in achieving fully-dense parts and controlling the microstructure. Aiming at overcoming these limitations, this study investigates the optimization of processing windows in blue laser-wire directed energy deposition (LW-DED). Owing to its short wavelength, the blue laser offers about 13 times more absorption in copper than the traditional infrared laser (IR) permitting more stable deposition conditions and enhanced process efficiency. LW-DED permits fabricating near-net shape components of medium up to large sizes as well as the reparation of end-of-life parts for a circular production. Nevertheless, the high thermal conductivity of CuCrZr leads to rapid heat dissipation during deposition which makes challenging its processing. Consequently, lack of fusion as well as anisotropic or coarse microstructures may be obtained. This study focuses on the influence of the blue laser DED strategy on melt pool behavior, porosity and microstructure development in order to optimize the processing window. For this purpose, conventional lab characterization combining microscopy and mechanical characterization is employed together with advanced high-energy synchrotron X-ray diffraction. The latter allows for detailed examination of the phases within the bulk and a time-resolved study of the microstructural evolution during mechanical loading.