Experiment Research On Laser Engineered Net Shaping Of 3D-flow Impeller Blade

3D-flow impeller is the key component of the turbine machinery, such as aero-engine and large scale compressor. As higher performance is required for the turbine machinery, the impeller becomes more complicated, which can be embodied by the thinner and more twisted blade. It is more difficult to manufacture the 3D-flow impeller. Up to date, the 3D-flow impeller is mainly manufactured by multi-axis milling and numerically controlled electrical discharge machining (NC-EDM) and both of them belong to subtractive method, which results in huge material waste and long processing cycle. Laser Engineered Net Shaping (LENS) is a novel rapid additive manufacturing technique, which provides an ideal platform to rapidly produce large three-dimensional parts with any complex geometry directly from the powders of metals, alloys or ceramics layer by layer. Therefore, there is great significance for its low cost, short cycle manufacturing, especially the rapid repair of the damaged impeller to manufacture the 3D-flow impeller by the LENS method.In this paper, one blade of the whole impeller is selected as the forming target and fundamental experiments are conducted to investigate the appropriate processing parameters. Besides, aiming at the large inclination and torsion angel of the blade, a method of preset angel between laser beam and vertical direction is proposed and forming experiments are carried out to investigate the appropriate range of the preset angle. Finally, based on the criteria of preset angle selection, the forming experiment is conducted to fabricate the whole impeller blade and its forming accuracy is analyzed. Main contents of the research are as follows:(1) The orthogonal experiment of single cladding bead is carried out to investigate the influence of the processing parameters on the morphology of the cladding bead and to obtain the appropriate process parameters; A mathematical model of the Z-increment is developed and the thin-walled structures with different Z-increment are prepared to verify the correct of the model, and finally a reasonable Z-increment is obtained.(2) On the condition that the optical axis perpendicular to the substrate, the thin-walled parts are prepared to investigate the limitation of the inclination angle. In addition, a method of preset angel between laser beam and vertical direction is proposed and forming experiments are carried out to investigate the criteria of the preset angle selection. Forming experiments of torsional thin-walled structures are conducted to verify the correct of the preset angle selection criteria.(3) According to the inclination angle, the impeller blade is divided into several parts and each part has an optimized preset angle. Based on the preset angle, the whole impeller blade is fabricated. Besides, the scanning model of the actual blade can be obtained and its forming accuracy can be analyzed by comparing its profile line with that of design model.