Enhancing surface quality of LPBF-manufactured aerospace components through chemical etching and non-destructive evaluation

Abstract

Laser Powder Bed Fusion (LPBF) presents significant technological advantages in the aerospace sector for producing intricate components like turbine blades and combustion chambers. However, challenges arise in achieving uniform surface qualities, particularly in downward-facing areas, where poor thermal conductivity of underlying powder leads to fusion defects and particle adhesions [1]. These problems are exacerbated for internal cavities because of the inability to perform postoperative treatment.

This study focuses on the LPBF manufacturing and surface post-treatments of cooling channels and film cooling holes. Special build strategies depending on the LPBF parameters, build orientations and geometries were developed to achieve a high geometric accuracy and surface quality already in the as-built condition. The channel and hole geometries were adapted specifically to the LPBF manufacturing method along the feature axis. Moreover, this study explores the use of chemical etching techniques with pressurized fluids that were employed to enhance the quality of internal surfaces in LPBF-manufactured components. These techniques necessitate meticulous evaluation through comparative analysis of original and treated surfaces in order to optimize the processes and avoid negative factors such excessive rounding of edges. Non-destructive evaluation, crucial for accurate assessment, involved synchrotron X-ray scanning followed by 3D reconstruction of objects pre- and post-etching. This method enabled qualitative analysis of film cooling holes with varying diameters, inclinations, and configurations for two variations of post-processing methods. From annular to fan-shaped widening or narrowing into a slit, the comparative equivalent diameters and surface curvature distributions facilitated precise diagnostics of posttreatment efficiency in LPBF-derived Inconel 718 internal channels.

This research contributes valuable insights into overcoming challenges associated with LPBF-manufactured aerospace components, offering a pathway to enhance surface quality and overall performance.