List of Abstracts 2018: SESSION G - ADDITIVE MANUFACTURING

Additive manufacturing has found a broad interest in the manufacturing community as a disruptive technology. Pros and Cons are now well understood in terms of economy and applicability. However the fundamental understanding of the most influencing parameters and the microstructural phenomena involved are not so well-known. Based on an assessment of laser weldability, problems and typical failures using different alloying systems are mentioned, which provides good criteria for material selection. Residual stresses and distortion are critical issues for further development of the SLM technology. New alloys and joining of hybrids are seen as a big challenge for the future.

Additive Manufacturing (AM) in the biomedicine may provides extensive customisation for the individual patient with optimized internal and surface structure. These methods are used for construction of 3D anatomical and physiological models, production of customized surgical implants, patient-specific surgical guides and external aids. However, production of medical devices has many specifications given by rather complex and strict legislative. Patient safety is the primary concern when introducing new manufacturing method or material. The aim of this study is to show particular applications and highlight the problems that limit the application of additive manufacturing in the clinical practice.

The open cell structure is commonly used in the medical device industry and consists of small struts connected to each other. Relatively new additive manufacturing technique “SLS” has been used in this study. This approach allows us to create small enough specimens to represent each strut in a commercially available orthopaedic porous structure. Pure titanium (Grade 2) powder has been used during the experiments because of higher resistance to corrosion and is one of the most biocompatible metal. The mechanical response of each strut affects the general behaviour of the porous system which influences stress shielding and bone attachment. In this research, small strut size effect and building direction of mechanical response have been investigated in order to provide vital data for upcoming rhombic dodecahedron structure FEM study.

As the Additive Manufacturing (AM) industry moves towards series industrial production, the need for standards covering all aspects of the technology becomes ever more prevalent. While standards and specifications for the various aspects of AM process chain continue to evolve, many such standards still need to be matured or are under consideration/development within standards development organizations (SDOs). This presentation will discuss the state of the AM standards including gaps, challenges, opportunities and insight based on a recent initiative to establish global center of excellence to support standard related research and development to be able to close the standardization gaps. Potential collaboration opportunities with the stakeholders and technical considerations in support of ongoing/future standards development will also be discussed.

The variability in mechanical properties in selective laser melted (SLM) maraging steel parts was captured by testing miniature size tensile coupons that were extracted from different locations in the part. Tensile testing provides better mechanical response to defects such as pores and inclusions as compared to hardness testing. The effect of heat treatment on the tensile property variation with different section thickness was also studied. It was observed that tensile property of miniature samples was more sensitive to porosity defects in maraging steel samples. The elongation values in the tensile specimens exhibited more variability as the section thickness of the part was reduced. This was due to the presence of more pore defects in thin wall sections. Heat treatment did not influence the tensile properties with respect to the wall thickness except for an increase in the strength due to hardening.

For wear demanding applications, the coating of WC in nickel based alloy is often used due to its excellent properties. Nevertheless, there are still limits of this coating, mainly deterioration of tungsten carbide due to heat load during laser cladding. The limits should be surpassed by the new type of coating consisting of the (TiW)C1-x in nickel based alloy. The goal of this study is to compare the microstructure and mechanical properties of these two coatings prepared by means of laser cladding.

AlSi9Cu3Fe alloy prepared by 3D printing has not been intensely studied so far. In this contribution, we characterize the microstructure of this alloy yielded by selective laser melting process (SLM); a 3D printing technique based on the localized melting of a powder material by a laser beam in thin successively deposited layers. The layer-wise building-up results in anisotropic and hierarchical microstructures. High cooling rates bring very fine microstructures, which results in high material strengths, but also residual stresses, which are undesirable. To reduce these stresses, various heat treatments are possible. We carried out stress-relief and T6 heat treatments to enhance the plasticity of the AlSi9Cu3Fe alloy prepared by SLM and studied their effect on the microstructure and mechanical properties. T6 heat treatment brought not only increase in plasticity but also in tensile yield strength.