Electropolishing of re-melted SLM stainless steel 316L parts using deep eutectic solvents: 3x3 full factorial design

The authors acknowledge the significant support provided by researchers from the Materials Centre, Department of Chemistry, University of Leicester (Dr Harris, Robert C., Dr Juma, Jamil ‎ and particularly Karl S. Ryder, Professor of Physical Chemistry). The affiliation of co-author A.A.Al-Barzinjy at time of submission of the article and duration of the experimental work, was the Materials Centre, Department of Chemistry, University of Leicester. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This three-level three-factor full factorial study describes the effects of electropolishing using deep eutectic solvents on the surface roughness of re-melted 316L stainless steel samples produced by the selective laser melting (SLM) powder bed fusion additive manufacturing method. An improvement in the surface finish of re-melted stainless steel 316L parts was achieved by optimizing the processing parameters for a relatively environmentally friendly electropolishing process using a Choline Chloride ionic electrolyte. The results show that further improvement of the response value-average surface roughness (Ra) can be obtained by electropolishing after re-melting to yield a 75% improvement compared to the as-built Ra. The best Ra value was less than 0.5 lm, obtained with a potential of 4 V, maintained for 30 min at 40 C. Electropolishing has been shown to be effective at removing the residual oxide film formed during the remelting process. The material dissolution during the process is not homogenous and is directed preferentially toward the iron and nickel, leaving the surface rich in chromium with potentially enhanced properties. The re-melted and polished surface of the samples gave an approximately 20% improvement in fatigue life at low stresses (approximately 570 MPa). The results of the study demonstrate that a combination of re-melting and electropolishing provides a flexible method for surface texture improvement which is capable of delivering a significant improvement in surface finish while holding the dimensional accuracy of parts within an acceptable range

Sliding Wear Characteristics and Corrosion Behaviour of Selective Laser Melted 316L Stainless Steel

Stainless steel is one of the most popular materials used for selective laser melting (SLM) processing to produce nearly fully dense components from 3D CAD models. The tribological and corrosion properties of stainless steel components are important in many engineering applications. In this work, the wear behaviour of SLM 316L stainless steel was investigated under dry sliding conditions, and the corrosion properties were measured electrochemically in a chloride containing solution. The results show that as compared to the standard bulk 316L steel, the SLM 316L steel exhibits deteriorated dry sliding wear resistance. The wear rate of SLM steel is dependent on the vol.% porosity in the steel and by obtaining full density it is possible achieve wear resistance similar to that of the standard bulk 316L steel. In the tested chloride containing solution, the general corrosion behaviour of the SLM steel is similar to that of the standard bulk 316L steel, but the SLM steel suffers from a reduced breakdown potential and is more susceptible to pitting corrosion. Efforts have been made to correlate the obtained results with porosity in theSLM steel

Design and Manufacture of Customised Denture Frameworks Using Magics®/Autofab® and SLM

Layer additive manufacturing technologies are progressing from rapid prototyping and rapid tooling. The development of finished parts made of metal powders without post processing is especially suitable for creation of precision part/object from small to mass customized fabrication; hence is the key application of these technologies. Laser based layer manufacturing techniques are mostly preferred in medical industry, particularly in the manufacture of denture frameworks; since these need to good mechanical properties and density. The introduction of new fibre and disc equipped system has significantly improved the accuracy of the processed components. The main objective of this work is to illustrate how this technology can be effectively used in the manufacturing of denture frameworks

On optimization of surface roughness of selective laser melted stainless steel parts: A statistical study

In this work, the effects of re-melting parameters for postprocessing the surface texture of Additively Manufactured parts using a statistical approach are investigated. This paper focuses on improving the final surface texture of stainless steel (316L) parts, built using a Renishaw SLM 125 machine. This machine employs a fiber laser to fuse fine powder on a layer-by-layer basis to generate three-dimensional parts. The samples were produced using varying angles of inclination in order to generate range of surface roughness between 8 and 20 µm. Laser re-melting (LR) as post-processing was performed in order to investigate surface roughness through optimization of parameters. The re-melting process was carried out using a custom-made hybrid laser re-cladding machine, which uses a 200 W fiber laser. Optimized processing parameters were based on statistical analysis within a Design of Experiment framework, from which a model was then constructed. The results indicate that the best obtainable final surface roughness is about 1.4 µm ± 10%. This figure was obtained when laser power of about 180 W was used, to give energy density between 2200 and 2700 J/cm2 for the re-melting process. Overall, the obtained results indicate LR as a post-build process has the capacity to improve surface finishing of SLM components up to 80%, compared with the initial manufactured surface.N/