Laser powder-directed energy deposition of CuCrZr using increasing LEPF approach: process development and characterization for mechanical and thermal properties

Laser Powder-Directed Energy Deposition (LP-DED) process offers potential scope in the fabrication of large-scale components and in the areas of remanufacturing technology. As the LP-DED process offers higher build volume and better control over the properties compared to other additive manufacturing techniques real-time critical components such as rocket nozzles, turbine blades, etc., can be fabricated. Fabrication of copper alloys using the LP-DED process is challenging due to the material’s poor laser absorptivity and unstable melt-pool dynamics. Hence, the current study focuses on developing a process map for fabricating sound CuCrZr deposits using the LP-DED process. Single-track analysis revealed that continuous and stable single tracks were achieved at low-power settings. Tracks with high power conditions exhibited keyhole porosity as a result of the vaporization of copper elements. However, low power conditions were not sufficient in the fabrication of bulk specimens as a result of variance in the cooling rate near the substrate (SS316L) and after deposition (CuCrZr). As a result, the increasing laser energy per unit feed (LEPF) approach was followed i.e., laser power of 200 W for the first three layers followed by 1000W for further layers. Fabricated samples exhibited superior density (97.5%) with no solute segregation (Cr or Zr). CuCrZr samples revealed long preferentially oriented columnar grains with < 111 > crystallographic texture extending parallel to the build direction. Tensile and thermal property testing revealed anisotropic behavior as a result of varying mean aspect ratios of the grains, dislocation density across planes, and the preferential orientation of the crystals.