Two-Step Laser Post-Processing for the Surface Functionalization of Additively Manufactured Ti-6Al-4V Parts

Abstract

Laser powder bed fusion (LPBF) is one of the additive manufacturing methods used to build metallic parts. To achieve the design requirements, the LPBF process chain can become long and complex. This work aimed to use different laser techniques as alternatives to traditional post-processes, in order to add value and new perspectives on applications, while also simplifying the process chain. Laser polishing (LP) with a continuous wave laser was used for improving the surface quality of the parts, and an ultrashort pulse laser was applied to functionalize it. Each technique, individually and combined, was performed following distinct stages of the process chain. In addition to removing asperities, the samples after LP had contact angles within the hydrophilic range. In contrast, all functionalized surfaces presented hydrophobicity. Oxides were predominant on these samples, while prior to the second laser processing step, the presence of TiN and TiC was also observed. The cell growth viability study indicated that any post-process applied did not negatively affect the biocompatibility of the parts. The presented approach was considered a suitable post-process option for achieving different functionalities in localized areas of the parts, for replacing certain steps of the process chain, or a combination of both.

A Novel Process for Manufacturing High-Friction Rings with a Closely Defined Coefficient of Static Friction (Relative Standard Deviation 3.5%) for Application in Ship Engine Components

“…The effects of altering the numbers of laser-scanning passes (5,10,15,20,25 and 30 passes) and pulse energies (0.36, 0.53 and 0.71 mJ) were studied. A plot of crater depth as a function of the number of laser passes for the three different pulse energies is shown in Figure 5, demonstrating an almost linear trend within the parameter space tested.…”

“…As a result, many research groups have focused their efforts on laser surface texturing to achieve different functional surfaces. This includes surface modification for aesthetic purposes [6,7], encryption of information [8], facilitating other processes (e.g., laser welding of dissimilar metals [9,10]), altering water-repellent properties [5,11,12], generating anti-icing [13] and anti-bacterial [14] surfaces, and modifying the tribological properties of surfaces, in particular reducing wear [15,16].…”

Laser polishing of additively manufactured metal parts: a review

“…The combination of the two steps resulted in hydrophobic characteristics for the surface. In the work, it has also been demonstrated that the biocompatibility of the parts isn't negatively affected despite the treatments [57].…”

Laser Additive Manufacturing for the Realization of New Material Concepts

“…However, in case of selective surface texturing or surface modification subtractive methods become more advantageous. Especially the combination of AM and laser ablation provide new opportunities in designing of 3D objects with local functionalities and biocompatibility as required for medical implants [9]. In section "14.4 -Laser Post-Processing of additive manufactured parts" recent progress in this approach will be presented and discussed referring to biomedical surfaces and Ventricular Assist Devices (VAD).…”

“…In addition to material development, additive manufacturing offers great design freedom in component design, which can be used, for example, for the development of load-optimized designs based on the bionic principle [5]. To add up to the versatility of additive manufacturing, laser post-processes can be used to modify the resulting surfaces of parts produced with such technology [6][7][8][9]. The different types of laser sources commercially available assure their suitability in a wide range of applications, with continuous wave (cw) lasers being often used for reduction of surface roughness, while pulsed lasers being applied in the modification of surface functionalities and to enhance the geometry accuracy.…”