Internal Surface Quality Enhancement of Selective Laser Melted Inconel 718 by Abrasive Flow Machining

Abstract

Additive manufacturing (AM) technology enables a new way for fabricating components with complex internal surfaces. Selective laser melting (SLM), being one of the most common AM techniques, is able to fabricate complex geometries with superior material properties. However, due to the poor surface quality, the fabricated internal surfaces cannot meet the specifications for some real applications. To achieve the required internal surface condition, post-polishing process is essential. As one of the most prominent processes for finishing inaccessible surfaces with a wide range of materials, abrasive flow machining (AFM) shows great potential to polish AM internal surfaces. Hence, this paper presents an analytical and experimental study on the internal surface quality improvement of SLM Inconel 718 by AFM, aiming to verify the feasibility of AFM on internal surface quality improvement. The surface evolution process was modeled, and the effects of process parameters on surface and subsurface quality were evaluated. The results show that good surface roughness was obtained at the medium conditions of high viscosity, large particle size, low extrusion pressure, and low temperature. The surface morphology was greatly affected by the medium particle size which showed consistency with the surface evolution model that small abrasive particles are unable to overcome the width and depth of the valleys, resulting in the formation of craters. The partially melt layer was effectively removed, and no subsurface damage was induced.

Experimental investigations into abrasive flow machining (AFM) of 3D printed ABS and PLA parts

“…balling effect and powder adhesion can also be removed by AFM (Ferchow et al, 2020;Mohammadian et al, 2018). Guo et al (Guo et al, 2020) also used the AFM process to finish SLM printed Inconel 718 parts. While using the AFM process to finish heat-treated and non-heat treated SLM printed parts, more plastic deformation in the form of pile-ups has been observed for non-heat treated parts (Duval-Chaneac et al, 2018).…”

The Post-Processing of Additive Manufactured Polymeric and Metallic Parts

“…Nano-level surface finishing results were also obtained by Wang et al [110] who studied the AFF process of parts produced by SLM and obtained a resultant roughness (Ra) of 940 nm compared to an initial 14 µm average surface roughness. Guo et al [111] applied abrasive flow machining to improve the surface of Inconel 718. The improved surface finish was achieved using a combination of low pressure, low temperature, high viscosity, and large particle size.…”

“…The tools' path is restricted so they cannot access intricate details of the parts Waste material May induce undesired deformation The material removal rate can be high [95][96][97][98][99][100][101] Abrasive jet finishing Can be applied in a micro and macro scale Can be applied to various shapes, complex surfaces, and geometries Not sensitive to the gap fluctuation between the nozzle and the workpiece The resultant surface roughness and material removal rate are easily controlled Improvement of the surface Slow tool wear without abrupt changes in the process accuracy Abrasives can be recycled More cost-effective compared to polishing, etching, and milling [94] Ultrasonic nanocrystal surface modification [102,103] Ultrasonic cavitation abrasive finishing [37,105] Abrasive flow finishing High initial MRR and decreased MRR with each successive cycle Rounding of the corners might be an issue [106][107][108][109][110][111][112][113] Magnetic-field-assisted finishing Magnetic abrasive finishing Self-sharpening Good flexibility, stability, and controllability Suitable for regular and complex geometries Suitable for a range of wide materials: resin, ceramics, metals, glass, etc. (mostly for hard materials)…”

Research on prediction method of surface roughness in weak magnetorheological shear thickening fluid polishing

“…The common research strategy has so far been to apply the theoretical prediction model and the finite element simulation model (both with experimental verification) to predict the processing quality so as to optimize the process of polishing methods [7]. Guo J et al [8] evaluated the influence of polishing flow viscosity, abrasive particle size, extrusion pressure, low temperature and other parameters on the processed surface and sub-surface quality by modeling the evolution process of Abrasive Flow Machining (AFM) micro-surface topography. Gorana V K et al [9] used the basic parameters of particle size, concentration, density, spacing and interparticle force in AFM to predict the value of post-processing surface roughness under different initial surface topographies.…”