Edward Chlebus

Fabrication of microscaffolds from Ti-6Al-7Nb alloy by SLM

Purpose – The purpose of this paper is to present the results of theoretical considerations and experimental tests concerning microscaffold fabrication by selective laser melting (SLM). Also described are manufacturing technologies for regular lattice microstructure with the smallest possible pore sizes and fullest possible order of geometric accuracy retained. Process parameters of SLM greatly affect the properties of the fabricated structures not only in regards to their material characteristics but also in their geometric representation accuracy. Design/methodology/approach – The paper discusses technological relationships between different laser micrometallurgy strategies and the accuracy of the manufactured microstructures. Findings – With technological possibilities evaluated, regular porous structure was created composed of cubic pores with cylindrical struts as their boundaries. Strut diameters are up to 180 μm, and the distance between neighboring strut axes was reduced to 600 μm, which gives a h...

Application of Ti6Al7Nb Alloy for the Manufacture of Biomechanical Functional Structures (BFS) for Custom-Made Bone Implants

Unlike conventional manufacturing techniques, additive manufacturing (AM) can form objects of complex shape and geometry in an almost unrestricted manner. AM’s advantages include higher control of local process parameters and a possibility to use two or more various materials during manufacture. In this work, we applied one of AM technologies, selective laser melting, using Ti6Al7Nb alloy to produce biomedical functional structures (BFS) in the form of bone implants. Five types of BFS structures (A1, A2, A3, B, C) were manufactured for the research. The aim of this study was to investigate such technological aspects as architecture, manufacturing methods, process parameters, surface modification, and to compare them with such functional properties such as accuracy, mechanical, and biological in manufactured implants. Initial in vitro studies were performed using osteoblast cell line hFOB 1.19 (ATCC CRL-11372) (American Type Culture Collection). The results of the presented study confirm high applicative potential of AM to produce bone implants of high accuracy and geometric complexity, displaying desired mechanical properties. The experimental tests, as well as geometrical accuracy analysis, showed that the square shaped (A3) BFS structures were characterized by the lowest deviation range and smallestanisotropy of mechanical properties. Moreover, cell culture experiments performed in this study proved that the designed and obtained implant’s internal porosity (A3) enhances the growth of bone cells (osteoblasts) and can obtain predesigned biomechanical characteristics comparable to those of the bone tissue.

Influence of laser power on the penetration depth and geometry of scanning tracks in selective laser melting

SLM technology allows production of a fully functional objects from metal and ceramic powders, with true density of more than 99,9%. The quality of manufactured items in SLM method affects more than 100 parameters, which can be divided into fixed and variable. Fixed parameters are those whose value before the process should be defined and maintained in an appropriate range during the process, e.g. chemical composition and morphology of the powder, oxygen level in working chamber, heating temperature of the substrate plate. In SLM technology, five parameters are variables that optimal set allows to produce parts without defects (pores, cracks) and with an acceptable speed. These parameters are: laser power, distance between points, time of exposure, distance between lines and layer thickness. To develop optimal parameters thin walls or single track experiments are performed, to select the best sets narrowed to three parameters: laser power, exposure time and distance between points. In this paper, the effect of laser power on the penetration depth and geometry of scanned single track was shown. In this experiment, titanium (grade 2) substrate plate was used and scanned by fibre laser of 1064 nm wavelength. For each track width, height and penetration depth of laser beam was measured.

Logistical Aspects of Transition from Traditional to Additive Manufacturing

The intensive growth and development of additive manufacturing affects all operations across the production chain. This article focuses on aspects of changes in logistics and supply chains during the transition from or replacement of traditional manufacturing with additive manufacturing, in new or existing enterprise. Today, hardware being shipped from far away and stored in a warehouse, that is still far from the end-user destination, generates high costs, but the digital file that just could be sent to one of the operational units closest to the customer could change that. Additive fabrication of an urgently required component located at place could overcome the lead time, shipping cost, inventory requirements and transport vulnerability.

The Effect of Rhenium Addition on Microstructure and Corrosion Resistance of Inconel 718 Processed by Selective Laser Melting

In this study, the effect of rhenium addition (2, 4, and 6xa0wtxa0pct) and building orientation (0 and 90xa0deg) on the microstructure and corrosion resistance of Inconel 718 (IN718) alloy processed by selective laser melting (SLM) was investigated. Microstructure characterization showed that the as-built IN718-Re alloys consist of columnar grains growing parallel to the building direction (Z-axis). Each columnar grain was characterized by a fine columnar/cellular dendritic substructure with Nb- and Mo-rich Laves phases and MC-type carbides embedded in the interdendritic spaces. Rhenium addition segregated to γ phase dendrites which resulted in an increase of the columnar/cellular substructures width with increasing Re content. Due to a strong microstructure anisotropy of SLM-processed IN718-Re alloys, the corrosion properties were examined for mutually perpendicular planes: XY (90xa0deg samples) and XZ (0xa0deg). The presence of rhenium enhanced the corrosion resistance of IN718 alloy in 0.1 M Na2SO4 and NaCl solutions at both exposed planes. The corrosion current density was significantly reduced for IN718-Re alloys and increasing Re content correlated with a more positive shift in corrosion potential. Moreover, the XY plane possessed better corrosion resistance than the XZ plane due to the higher fraction of laser overlapping areas observed for the XZ plane.

Porosity Detection by Computed Tomography

Industrial computed tomography (CT) supports quality inspection of manufactured technical objects and product development thanks to its possibility of non-destructive detection of porosity. Application of computed tomography to porosity detection permits not only qualitative evaluation of internal structure of objects, but also quantitative evaluation of material porosity with representation of three-dimensional shape of pores and their spatial distribution. The paper presents a brief characteristic of the factors influencing effectiveness of porosity detection by CT. A technical example illustrates influence of the applied magnification on the possibility to detect porosity and represent shapes of pores. Next, the results of porosity evaluation obtained by CT and by standard microscopic examinations are compared. It was demonstrated that result of porosity detection is influenced by magnification and resolution of CT measurements.