Laser and Electron Beam Additive Manufacturing Methods of Fabricating Titanium Bone Implants

Abstract

Featured Application: This work is a detailed comparison of the direct laser and electron additive manufacturing methods, which could help scientific research institutes and companies choose the best 3D printer system for the fabrication of titanium implants.Abstract: Additive Manufacturing (AM) methods are generally used to produce an early sample or near net-shape elements based on three-dimensional geometrical modules. To date, publications on AM of metal implants have mainly focused on knee and hip replacements or bone scaffolds for tissue engineering. The direct fabrication of metallic implants can be achieved by methods, such as Selective Laser Melting (SLM) or Electron Beam Melting (EBM). This work compares the SLM and EBM methods used in the fabrication of titanium bone implants by analyzing the microstructure, mechanical properties and cytotoxicity. The SLM process was conducted in an environmental chamber using 0.4-0.6 vol % of oxygen to enhance the mechanical properties of a Ti-6Al-4V alloy. SLM processed material had high anisotropy of mechanical properties and superior UTS (1246-1421 MPa) when compared to the EBM (972-976 MPa) and the wrought material (933-942 MPa). The microstructure and phase composition depended on the used fabrication method. The AM methods caused the formation of long epitaxial grains of the prior β phase. The equilibrium phases (α + β) and non-equilibrium α' martensite was obtained after EBM and SLM, respectively. Although it was found that the heat transfer that occurs during the layer by layer generation of the component caused aluminum content deviations, neither methods generated any cytotoxic effects. Furthermore, in contrast to SLM, the EBM fabricated material met the ASTMF136 standard for surgical implant applications.

Comprehensive Evaluation of the Biological Properties of Surface-Modified Titanium Alloy Implants

“…Analysis of the XPS data confirmed that the surface of the TNT5 coating formed by a layer of titanium oxide, in which the titanium oxidation state is +4 (TiO 2 -100%). Meanwhile, the surface TNT15 layer should be treated as a mixture, which consists of Ti 4+ (TiO 2 -86%) and Ti 3+ (Ti 2 O 3 -14%) oxides (Tables 1 and 2, Figure S1) [43]. However, considering the earlier reports, we can assume that in water solutions, unstable oxides of titanium on the lower oxidation states will be oxidized up to TiO 2 [44], and therefore in all biological experiments TNT15 can also be treated as a TiO 2 layer.…”

Tensile and Creep Properties Improvement of Ti-6Al-4V Alloy Specimens Produced by Electron Beam Powder Bed Fusion Additive Manufacturing

“…Consequently, there are different crystallization conditions for the two methods. In general, the highest cooling rates, reached during the L-PBF process, enhance mechanical strength; however, the highest temperature gradients due to L-PBF, in comparison to EB-PBF, led to internal stress at small scale level [14].…”

Tribocorrosion Behaviour of Ti6Al4V Produced by Selective Laser Melting for Dental Implants

“…The wear rate for the synergism created is higher than the sum of each individual action [7][8][9][10][11][12][13][14]. Additive manufacturing (AM) methods are processes that fuse materials layer by layer, to produce items based on 3D model data [16] and allows rapid prototyping and direct fabrication of metallic implants. A particular example of the above mentioned AM methods is selective laser melting (SLM) that is considered the most popular and commercially-available powder bed fusion AM method [16].…”

“…In SLM, metallic powders are uniformly spread on the building platform by a rake. A focused laser beam, usually CO 2 (10.6-µm wavelength) or Nd:YAG (1.06-µm wavelength) scans the surface according to the prescribed path and selectively melts the powders in this layer, after which a new layer of powders is spread after lowering the building platform to the distance of the layer thickness (in the scale of tens of microns) [16,17].…”