Research on laser engineered net shaping of thick‐wall nickel‐based alloy parts

Abstract

PurposeThe paper seeks to investigate the laser engineered net shaping (LENS) of metal thick‐wall parts from Ni‐based alloy powders.Design/methodology/approachThe composition of Ni‐based alloy powders was determined from phase diagram, which was 84Ni14.4Cu1.6Sn. The powders were prepared by gas atomization. Deoxygenation and screen separation were applied to the powders to improve the sintering ability and narrow the particle size distribution before shaping. Thick‐wall metal parts were built by LENS under different conditions. The microstructures, surface morphologies of the prepared parts were characterized.FindingsThe gas atomized powders were almost uniformly spherical after sieving. Most of oxygen contained in the alloy powders could be removed in H2 atmosphere for heating at 550°C for 2 h. These nickel‐based alloy powders with 150‐200 mesh size were suitable for powder feed system. And these powders were shaped successfully by LENS. Thick‐wall parts with thickness ranged from 20 to 25 mm were fabricated. The thickness of each layer was between 400 and 600 μm by scanning electron microscope. Metallographs revealed that dendritic structures with different characteristics were grown on XY‐, YZ‐ and XZ‐section.Research limitations/implicationsThe present experiments were limited by the atmosphere control during the LENS process. The oxide at the interface between two neighbor layers could decrease the mechanical properties if without good inert gas protection, such as a protective atmosphere chamber.Originality/valueThis paper describes a refined experimental program that is needed to resolve the remaining technical issues in LENS of thick‐wall parts. The nickel‐based alloy powders suitable for the LENS process were studied and prepared. After pretreatment, the self‐made powders have good shaping ability. Microstructure features were first discussed with the variation of the face orientation. The dendrite arm distance obtained by this experiment is between 8 and 20 μm, well conforming to the theory. The thick‐wall parts with dense structures were fabricated successfully to widen the field of application of LENS.