Laser powder bed fusion (LPBF) is a promising technology that requires further work to improve productivity to be adopted more widely. One possible approach is to increase the laser power and scan speed. A customized high-speed and high-power LPBF system has been developed for this purpose. The current study investigated the surface roughness and near-surface porosity as a result of unsupported overhangs at varying inclination angles and orientations during the manufacturing of Ti6Al4V parts with this custom high-speed and high-power LPBF system. It is known that surface roughness and porosity are among the main drawbacks for parts manufactured by LPBF, and that supports are required for overhang regions with low inclination angles relative to the powder bed, typically in commercial LPBF systems requiring supports for regions with inclination angles less than 45°. However, the appropriate inclination angles for this custom system with high power and speed requires investigation. In this article, a simple benchmark test artefact with different inclination angles was manufactured in different orientations on the build platform and characterized by X-ray tomography, touch probe roughness meter, optical microscopy, and scanning electron microscopy. The analysis of surface roughness and near-surface porosity at upskin and downskin regions was performed as a function of inclination angle. The results indicate that the high-speed LPBF process produces relatively high roughness in all cases, with different porosity distributions at upskin and downskin areas. Both roughness and porosity vary as a function of inclination angle. Significant warping was observed, depending on build orientation relative to laser scanning direction. These are the first reported results of the detailed surface roughness and porosity characterization of part quality from such a high-speed, high-power LPBF process.

中文翻译：

---

高速激光粉末床熔融产生的无支撑悬垂物的粗糙度和近表面孔隙率

激光粉末床熔融（LPBF）是一项很有前景的技术，需要进一步努力以提高生产率，才能得到更广泛的采用。一种可能的方法是增加激光功率和扫描速度。为此，我们开发了定制的高速、高功率 LPBF 系统。当前的研究调查了在使用这种定制的高速和高功率 LPBF 系统制造 Ti6Al4V 零件期间，由于不同倾斜角度和方向的无支撑悬伸而导致的表面粗糙度和近表面孔隙率。众所周知，表面粗糙度和孔隙率是 LPBF 制造的零件的主要缺点之一，并且相对于粉末床倾斜角度较低的悬垂区域需要支撑，通常在商用 LPBF 系统中，需要为倾斜角度较小的区域提供支撑。大于45°。然而，这种具有高功率和高速度的定制系统的适当倾斜角度需要研究。在本文中，在构建平台上以不同方向制造了具有不同倾斜角度的简单基准测试制品，并通过 X 射线断层扫描、接触式探针粗糙度计、光学显微镜和扫描电子显微镜进行了表征。上皮和下皮区域的表面粗糙度和近表面孔隙率作为倾斜角的函数进行分析。结果表明，高速 LPBF 工艺在所有情况下都会产生相对较高的粗糙度，并且皮上和皮下区域的孔隙率分布不同。粗糙度和孔隙率都随着倾斜角的变化而变化。根据相对于激光扫描方向的构建方向，观察到明显的翘曲。这是首次报道的通过这种高速、高功率 LPBF 工艺对零件质量进行详细表面粗糙度和孔隙率表征的结果。