Application of Laser Surface Polishing on Additive Manufactured Parts of Inconel 718 Nickel-Based Superalloy

Abstract

This article deals with the influence of laser polishing parameters on the final surface quality of nickel-based superalloy Inconel 718 produced by metal additive manufacturing. The aim is to optimize the laser polishing process parameters to reduce the surface roughness of the sample. The investigated parameters of the laser are scanning speed, frequency, focal length, and pulsed and continuous wave regimes are considered. The samples of Inconel 718 are produced by direct metal laser sintering technology. Depending on the printing orientation, the roughness after AM is Ra 5 -12 µm. The samples were machined to ensure uniformity of the monitored and tested surface. An IFM -G4 3D optical microscope is used for the surface evaluation. The initial roughness of the samples before applying laser polishing was Ra 1 -2 µm. The roughness after laser polishing is significantly reduced to Ra 0.369 µm.

Influence of Overlap on Surface Quality in the Laser Polishing of 3D Printed Inconel 718 under the Effect of Air and Argon

“…A visual inspection, as well as SEM observation, revealed the formation of substantial dot-like oxides on the surface polished with 50% to 80% of overlap in ambient air (a similar phenomenon was previously seen on IN718 by Bures and Zetek [ 32 ], but it is yet to be characterized). From 85% to 90%, the effect of these oxides can be considered to be minor due to the fact they mostly appear on the edges of the polished areas.…”

“…Bures and Zetek conducted CW-LP on 3D printed IN718 and observed the formation of oxides. They also noted that the oxidation layer effects the surface roughness [ 32 ]. Therefore, most of the LP experiments are conducted in an argon atmosphere to prevent oxidation of the surface.…”

Pulsed laser polishing of selective laser melted aluminium alloy parts

“…Likewise, with regard to the AM nickel based superalloys, LP helped reducing average roughness Ra and 5-point average roughness Rz of SLM Inconel 718 samples from 7.5 μm and 31 μm to less than 0.1 μm and 0.6 μm, respectively [21]. A relatively lower percentage reduction (72%) in roughness was observed by Bures and Zetek [22] when employing LP on Inconel 718 surfaces produced via SLM, followed by machining.…”

Laser polishing of additively manufactured metal parts: a review

“…They observed an improvement in the surface roughness when laser frequency increases until 200 kHz while after this value Ra increases. Bures et al [76] investigated the LP performances on DMLSed Inconel 718 samples by considering both pulsed and continuous wave regimes. Concerning the pulsed regime, the best surface roughness was achieved with process parameters of 30 kHz and 500 mm s −1 that allowed to improve the surface by 56% to Ra = 0.5257 µm.…”