As a core hot-end component serving in extreme environments characterized by high temperature, high pressure, and high corrosiveness, the profile accuracy and surface integrity of aero-engine turbine blades directly determine the engine’s thrust-to-weight ratio, aerodynamic efficiency, and service safety. IN718 nickel-based superalloy has emerged as the preferred material for turbine blades owing to its excellent high-temperature strength, creep resistance, and corrosion resistance. When fabricating IN718 nickel-based superalloy turbine blades via laser powder bed fusion (LPBF) additive manufacturing, uneven molten pool solidification and interlayer stacking errors tend to induce defects such as excessive surface roughness and airfoil dimensional deviations exceeding allowable tolerances. These defects impair the blade’s aerodynamic precision and high-temperature service reliability, thereby restricting its engineering applications. To address this challenge, this study aims to overcome the accuracy limitations of standalone additive manufacturing and proposes an integrated hybrid process combining LPBF near-net shaping technology with five-axis CNC precision machining. This approach achieves high-precision and high-surface-quality forming of IN718 alloy turbine blades, meeting the service requirements of high-end aero-engine equipment.

Aviation-grade IN718 nickel-based superalloy powder was adopted as the forming material, and a full-process workflow of "additive manufacturing-machining-inspection" was established. First, LPBF process parameters were optimized via orthogonal experiments (laser power: 270 W, scanning speed: 900 mm/s, powder layer thickness: 0.04 mm, scanning spacing: 0.08 mm) to achieve the near-net shaping of turbine blade blanks. Subsequently, five-axis high-speed machining was employed for precision milling: a cutting path was designed specifically for the complex free-form surface of the blade airfoil, and a micro-machining strategy was adopted for key regions (including the pressure side, suction side, leading edge, and trailing edge) with parameters set as follows: cutting speed of 1500 mm/min, feed rate of 0.04 mm/r, and cutting depth of 0.12 mm. This strategy effectively avoided machining deformation and edge chipping. To systematically evaluate the forming quality, a multi-dimensional inspection system was constructed: a 3D laser scanning measuring instrument was used for dimensional deviation analysis, while a 3D optical profilometer was employed to characterize surface roughness and microtopography. Meanwhile, a control group fabricated solely by LPBF was established. By comparing the dimensional accuracy, surface quality, and microstructure of samples from the two groups, the regulatory effect and underlying mechanism of the hybrid process were quantitatively analyzed.

Experimental results verified the superiority of the hybrid process, achieving a breakthrough improvement in turbine blade forming quality. Before machining, the average airfoil dimensional deviation exceeded the allowable tolerance (greater than ±0.1 mm). After machining, all average deviations fell within the allowable range, fully meeting the design accuracy requirement of ±0.1 mm for turbine blades (Fig.9). The surface roughness R_a was reduced from the initial 8.2 μm~11.2 μm to 0.6 μm～0.9 μm, with an improvement rate of over 90% (Fig.14). The surface microtopography exhibited uniform and smooth cutting textures without obvious scratches or machining damage (Fig.15). The key innovation lay in achieving precise matching of process parameters between LPBF near-net shaping and five-axis machining, which addressed the industry-wide problem of machining deformation and precision loss of complex curved parts after additive manufacturing, and provided a new approach for the efficient manufacturing of precision superalloy components.

This study systematically clarifies the regulatory control mechanism of the hybrid process. In the LPBF stage, parameter optimization ensures blank density and basic form-and-position accuracy. In the five-axis machining stage, precise cutting removes surface defects and dimensional deviations, achieving synergistic improvement in forming efficiency and quality. The research results not only verify the feasibility and superiority of the hybrid process in manufacturing IN718 alloy turbine blades but also establish principles for process matching between additive manufacturing and traditional precision machining. This provides a theoretical basis and engineering technical support for the efficient manufacturing of precision and complex components made of difficult-to-machine materials such as superalloys and titanium alloys. Additionally, the hybrid process significantly shortens the blade manufacturing cycle and reduces production costs, which is of great significance for promoting the industrial application of hybrid additive-subtractive manufacturing technology in key components of high-end equipment (e.g., aero-engine blades and combustion chambers). Meanwhile, it provides technical support for the independent and controllable production of core components in China’s aerospace field.