A Review of Metal Fabricated with Laser‐ and Powder‐Bed Based Additive Manufacturing Techniques: Process, Nomenclature, Materials, Achievable Properties, and its Utilization in the Medical Sector

Abstract

Additive manufacturing has multiple advantages over conventional fabrication techniques, such as the geometrical freedom and, to a great extent, the omission of tooling equipment. Hence, futuristic designs and non-standard topology-optimized structures can be fabricated without causing noteworthy extra cost, since the geometrical complexity is, exaggeratedly spoken, for free. The manufacturing time and the amount of required raw material are the key criteria, which determine the expenses. What at first glance appears as an engineer's dream, introduces its complexity in the description of the material's characteristics and their volatility to the manufacturing conditions. Within this study, the main properties (i.e., surface hardness, tensile, and compression strength, as well as fracture toughness) and their anisotropic and inhomogeneous nature are addressed. Detailed overviews of the progress to date for aluminum, iron, titanium, cobalt, and nickel based raw materials are provided. Furthermore, an overview about the state-of-the-art in the medical sector is included, comprising the areas of utilization and several trail studies.

Tensile strength performance with determination of the Poisson‘s ratio of additively manufactured AlSi10Mg samples

“…Additive manufacturing is an interesting alternative especially for prototypes, especially for those with a complex geometry for machining, rendering the prototype production in die-casting very costly. The selective laser melting process belongs to the family of layered, powder bed-based additive manufacturing technologies and has emerged from the older selective laser sintering process [1]. The use of additive manufacturing processes allows and realizes an unseen freedom in design, enables undercuts and cavities, which are problematic in conventional fabrication procedures.…”

“…The heated material creates a melt pool and solidifies rapidly. In order to avoid undesired oxidation reactions, the process is performed in an inert gas environment, whereby the residual oxygen content is monitored continuously throughout the process [2]. The layered structure allows a high flexibility in geometry and design on one the hand, but causes directional dependencies reasoned in the layer-wise fabrication on the other hand [3].…”

On the Anisotropic Mechanical Properties of Selective Laser Melted Stainless Steel

“…Both values were exceeded by far, yet the 40% minimum breaking elongation of bulk 1.4404 is a criterion which was only achieved by one out of seven configurations. One other aspect which should be emphasised is the greatly reduced difference between the yield point and the ultimate tensile strength caused by AM [8]. In Table 7, several achieved ratios are compared with the bulk material.…”

“…Since the full melting of the raw metal powder enables the generation of fully dense parts within a single production step, with mechanical properties exceeding the specifications of the conventional material, the fabrication of highly specialized components (like tools, moulds, ultra-lightweight components or medical implants) via AM is on the rise [4][5][6][7]. One of the major challenges is, to date, the characterization and prediction of the properties of additively manufactured structures and their linkage with the selected fabrication settings [8]. The most utilized approach to describe the manufacturing process is via the energy input of the laser beam per unit volume, commonly referred to as the energy density [9].…”

Crystallographic Features of Microstructure in Maraging Steel Fabricated by Selective Laser Melting

“…The tensile ductility of SLM-fabricated alloys (Al, Ni, and Co alloys [31]) depends on the building direction, which is responsible for preferential fracturing along the melt pool boundaries [16,17,32]. However, in the SLM-fabricated maraging steel, the tensile ductility is apparently independent of direction [33] because the retained γ phase that is localized at the melt pool boundaries could suppress the preferential fracture along the melt pool boundaries.…”