Abstract Insufficient surface quality is one of the common issues encountered in laser powder bed fusion (LPBF). In order to meet the industrial requirements, it is typically necessary to proceed to expensive and time-consuming post-processing. Improving surface quality during the building process would hence be very beneficial. However, in-situ remelting (laser polishing) is possible only for horizontal up-facing surfaces. The quality of inclined surfaces remains limited to the as-built state, as after building they are covered with loose powder, excluding the possibility for in-situ polishing. This work presents a novel strategy to improve the quality of up-facing inclined surfaces using a dual-laser setup with a continuous wave and a pulsed laser. This approach consists in two steps: after building, the powder is selectively removed from the inclined surfaces using shock waves generated by a nanosecond pulsed laser. These newly exposed surfaces can be subsequently remelted with a continuous wave laser or alternatively treated with a pulsed laser. This paper discusses various scanning strategies for selective powder removal, their efficiency and the surface quality of the treated parts. The initial results are promising and indicate that the surface texture of LPBF parts in maraging steel 300 can be significantly improved for surface inclinations up to 45 ° , provided a sufficient powder removal efficiency is reached. The latter was found to be dependent on the maximal depth and volume of the powder to be removed, but also on part geometry.

中文翻译：

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激光激波与原位激光重熔相结合的LPBF零件上斜面质量改进新策略

摘要 表面质量不足是激光粉末床融合（LPBF）中遇到的常见问题之一。为了满足工业要求，通常需要进行昂贵且耗时的后处理。因此，在建造过程中改善表面质量将是非常有益的。然而，原位重熔（激光抛光）仅适用于水平朝上的表面。斜面的质量仍然仅限于完工状态，因为建成后它们会被松散的粉末覆盖，排除了原位抛光的可能性。这项工作提出了一种使用连续波和脉冲激光的双激光装置来提高向上倾斜表面质量的新策略。这种方法包括两个步骤：在构建之后，使用纳秒脉冲激光产生的冲击波从倾斜表面选择性地去除粉末。这些新暴露的表面随后可以用连续波激光重新熔化，或者用脉冲激光处理。本文讨论了用于选择性除粉的各种扫描策略、它们的效率和处理过的零件的表面质量。初步结果是有希望的，表明如果达到足够的除粉效率，马氏体时效钢 300 中 LPBF 零件的表面纹理可以显着改善，表面倾角高达 45°。发现后者取决于要去除的粉末的最大深度和体积，但也取决于零件的几何形状。这些新暴露的表面随后可以用连续波激光重新熔化，或者用脉冲激光处理。本文讨论了用于选择性除粉的各种扫描策略、它们的效率和处理过的零件的表面质量。初步结果是有希望的，表明如果达到足够的除粉效率，马氏体时效钢 300 中 LPBF 零件的表面纹理可以显着改善，表面倾角高达 45°。发现后者取决于要去除的粉末的最大深度和体积，但也取决于零件的几何形状。这些新暴露的表面随后可以用连续波激光重新熔化，或者用脉冲激光处理。本文讨论了用于选择性除粉的各种扫描策略、它们的效率和处理过的零件的表面质量。初步结果是有希望的，表明如果达到足够的除粉效率，马氏体时效钢 300 中 LPBF 零件的表面纹理可以显着改善，表面倾角高达 45°。发现后者取决于要去除的粉末的最大深度和体积，但也取决于零件的几何形状。它们的效率和处理过的零件的表面质量。初步结果是有希望的，并且表明如果达到足够的除粉效率，马氏体时效钢 300 中 LPBF 零件的表面纹理可以显着改善，表面倾角高达 45°。发现后者取决于要去除的粉末的最大深度和体积，但也取决于零件的几何形状。它们的效率和处理过的零件的表面质量。初步结果是有希望的，并且表明如果达到足够的除粉效率，马氏体时效钢 300 中 LPBF 零件的表面纹理可以显着改善，表面倾角高达 45°。发现后者取决于要去除的粉末的最大深度和体积，但也取决于零件的几何形状。