Laser Polishing of Additive Manufactured Aluminium Parts by Modulated Laser Power

Abstract

In this study a new approach to laser polishing with periodic modulated laser power in the kilohertz regime is introduced. By varying the modulation frequency and modulation time, different periodic laser power curves with varying minimum, peak and average laser power can be created. The feasibility of the method is shown by polishing of vertical built AlSi10Mg L-PBF parts with an initial roughness of Ra = 12.22 µm. One polishing pass revealed a decreasing surface roughness with increasing energy density on the surface up to Ra = 0.145 µm. An increasing energy density results in a rising remelting depth between 50 and 255 µm and a rising relative porosity of 0.3% to 4.6%. Furthermore, the thermal process stability, analysed by the melt pool length in scanning direction, reveals a steadily increasing melt pool dimension due to component heating. Multiple laser polishing passes offers a further reduced surface roughness, especially at higher modulation frequencies and provides an improved orientation independent roughness homogeneity. The process stability regarding varying initial surface roughness revealed an almost constant relative roughness reduction rate with an achievable roughness variation after two polishing passes between Ra = 0.13–0.26 µm from an initial state of Ra = 8.0–19.2 µm.

Recent Advancements in Post Processing of Additively Manufactured Metals Using Laser Polishing

“…Furthermore, corrosion-resistant austenitic X2CrNiMo17-12-2 steel was investigated [85]. For PW, the optimized result was achieved when the laser diameter was measured at 12 mm and intensity at 1.74 kW/mm 2 .…”

Advances in the design and manufacturing of novel freeform optics

“…Reprinted from [19] © Optical Society of America under the terms of the OSA Open Access Publishing Agreement. Reproduced from [20]. CC BY 4.0.…”

Influence of Laser Polishing on the Material Properties of Aluminium L-PBF Components

“…Laser polishing of additive manufactured metal parts revealed high roughness reduction rates on a broad range of metal alloys such as Cobalt-Chromium alloys (CoCr) [12][13][14], Inconel 718 [15,16], tool steel H13 [17], maraging steel 1.2709 [18], Titanium Ti6Al-4V [19][20][21] and corrosion resistant steel 316 L [22,23]. The laser polishing of L-PBF-aluminium AlSi10Mg parts with different laser operation modes has already been comprehensively investigated with roughness reduction rates above 98% Ra of the initial surface roughness [24][25][26][27][28][29]. Due to low laser beam absorption of Al-Si alloys and, at the same time, high process energy losses due to comparatively high thermal conductivity, high intensities and energy densities are required for laser polishing.…”