Numerical, Mechanical, and Metallurgical Investigation of an Innovative Near Net Shape Titanium Selective Laser Melting Engine Component and Comparison with the Conventional Forged One

Abstract

As is well known today, additive manufacturing (AM) is a process of joining materials to make objects from 3D model data as opposed to subtractive manufacturing methodologies which remove material. [1] In general, AM technology allows the manufacturing of parts directly from digital model by depositing the material through a layer-by-layer approach that is digitally controlled. This emerging technology can manufacture metallic components with high precision. Among the main advantages, it can be found freedom of part design, part complexity, lightweighting, part consolidation, and design for specific functions. In light of this, AM technologies could provide an optimal trade-off between the need to increase manufacturing speed for highly customized and complex parts while achieving required mechanical properties with near net shaped components containing fewer defects. All these aspects are of interests in metal AM for aerospace, oil and gas, marine, and transport applications. [2] Among these processes, particularly selective laser melting (SLM) is one of the most used. This is a powder bed fusion process that uses metal powder, mainly for the manufacturing of components belonging to the biomedical and automotive field. [3][4][5] SLM has the great benefit to generate very complex shapes [6] that are often impossible to be produced with the conventional technologies. Thus, near net shape (NNS) parts and undercuts can be now easily created with this new technology. Another SLM benefit could be the creation of internal passages by maintaining a good dimensional control; this could be used, for example, for the integration of cooling channels. A first benefit that can be gathered is the reduction of metalworking operation. In the automotive field, the opportunity to create lightweight components [7][8][9] due to a NNS design is even more important. Indeed, this is one of the most feasible measures to reduce the vehicle emissions [10][11][12] and consequently the traffic-related air pollution. As mentioned earlier, it is clearly the need to modify how engineers think when designing parts; the typical design of traditional subtractive manufacturing processes is very different from the new shapes achievable with AM. [13] Thus, to take full advantage of unique capabilities from AM processes, specific Design for Additive Manufacturing (DfAM) methods are needed. Typical DfAM includes topology optimization and other design methods which can be supported by AM-enabled features. In the automotive domain, SLM is currently limited for the production of prototypes or rare spare parts, while research is moving toward a larger adoption of this technology, [14,15] for example, targeting the production of components for high-end and luxury vehicles.

Wear and Corrosion Characterization of a Ti–6Al–4V Component for Automotive Applications: Forging versus Selective Laser Melting Technologies

“…Further details about the microstructure can be found in previous studies. [ 1,2 ] The volume fraction of β phase calculated from image analysis is slightly higher for the forged samples under investigation (26 ± 4%) than for SLM ones (22 ± 5%).…”

“…Further details about the microstructure can be found in previous studies. [1,2] The volume fraction of β phase calculated from image analysis is slightly higher for the forged samples under investigation (26 AE 4%) than for SLM ones (22 AE 5%). The different microstructures observed between the two processes are well noted [32,33] and are mainly related to the wide dissimilarities and kinetics in the production technologies which influence the phases shape, dimension, and distribution.…”

“…The investigation has proved that both the SLM and forged macrostructures presented equiassic and isotropic behavior, and the mechanical properties were verified to be aligned with the design targets. [ 2 ]…”

“…In brief, the first research [ 1 ] was focalized on the evaluation of the selective laser melting (SLM) introduction for serial application, testing three different types of heat treatments on Ti–6Al–4V as‐received samples; this mechanical and metallurgical study allow to identify a set of heat treatment parameters that guarantee the achievement of the required targets concerning these properties in the automotive field. Progressively the project was focused on the possibility to develop [ 2 ] a Ti–6Al–4V NNS engine component, exactly a connecting rod produced by SLM. This study led to an additional weight reduction (about 15%), thanks to the the substitution of original “H” section of the forging conrod with an multi‐branches structure, achievable only by AM technology.…”

“…The present research article is part of an ongoing project that has the objective to develop an additive manufactured connecting rod in Ti-6Al-4V in substitution of the traditional forged one made of the same alloy. [1][2][3] For the sake of clarity, a connecting rod has to transmit the force of the engine piston to the crankshaft and convert the transverse motion of the former into rotation of the latter; thus, mechanical resistance and lightness are fundamental items. The most common material used for this mechanical element is steel, recently substituted with titanium, forged, or machined from a block, to reduce the weight.…”