## 2 Materials and Methods  
For the study, samples were printed from Ti6 Al4V powder (EOS Titanium Ti64-Table 1) using DMLS additive manufacturing on an EOS M100 printer (EOS GmbH, Krailling Germany)--as shown in Figure 1. The particle size range for the initial powder used was 39 \(\pm\) 3 \(\upmu\)m. Each sample had two contours, 100% fill with the maximum laser beam power being 200 W, with parameters set at Ti64 20 \(\upmu\)m FlexLine 1.x, a volume rate of 1.68 mm\({}^{3}\)/s, and a layer thickness of 20 \(\upmu\)m. Details of the process parameters are proprietary to EOS [17; 18; 19; 20].  
To remove the unmelted metal powder, the samples were sandblasted in a Renfert \"VARIObasic\" cabin sandblaster. Glass beads ranging from 90 \(\upmu\)m to 150 \(\upmu\)m fed through a nozzle at a pressure of 6 bar were used for the process. The samples were sandblasted for  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**O [\%]** & **V [\%]** & **Al [\%]** & **Fe [\%]** & **H [\%]** & **C [\%]** & **N [\%]** & **Y [\%]** & **Ti [\%]** \\ \hline max 0.130 & 3.500–4.500 & 5.500–6.500 & max & 0.250 & max 0.012 & max 0.080 & max 0.050 & max 0.005 & balance \\ \hline \hline \end{tabular}
\end{table}
Table 1: Chemical composition of Ti64 powder-wt.-% [17].  
Figure 1: DMLS-printed samples with a diameter of 14 mm.  
120 s at an angle of 45 degrees. In turn, the heat treatment was then carried out in the high vacuum furnace \"AMAZEMET inFURNER\" with the following process parameters:  
* The furnace was heated to 800 \(\pm\) 10 \({}^{\circ}\)C, held the samples for 2 h, and was then tempered to 500 \({}^{\circ}\)C, followed by slow cooling to room temperature--as shown in Figure 2a;
* The furnace was heated to 910 \(\pm\) 10 \({}^{\circ}\)C, held the samples for 2 h, and the samples were then cooled with the furnace to room temperature--as shown in Figure 2b.
* The furnace was heated to 1020 \(\pm\) 10 \({}^{\circ}\)C, held the samples for 2 h, and the samples were then cooled with the furnace to room temperature--as shown in Figure 2c.  
All the samples were cleaned in a Struers Lavamin ultrasonic cleaner. Some of the samples were subjected to mechanical polishing on a Struers Tegramin-30 automatic grinder-polisher. For this purpose, the specimens were included in an automatic \"Struers CitoPress-30\" press in Struers' polypropylene resin with mineral and wood flour additives \"Purifast\" at a temperature of 150 \({}^{\circ}\)C, for a time of 3 min, and at a pressure of 250 bar. Subsequently, sanding was carried out on abrasive papers with gradations of P320, P800, and P1200 and mechanical polishing was carried out using an automatic sander-polisher Tegramin-30 from Struers with the following surface treatment parameters on a silicon oxide polishing cloth. The samples were divided into groups--as shown in Table 2.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & S & sandblasting—initial state \\ \cline{2-3}  & S\_800 & sandblasting + heat treatment\_800 \({}^{\circ}\)C \\ \cline{2-3}
**Group I** & S\_910 & sandblasting + heat treatment\_910 \({}^{\circ}\)C \\ \cline{2-3}  & S\_1020 & sandblasting + heat treatment\_1020 \({}^{\circ}\)C \\ \hline \hline  & MP & mechanical polishing—initial state \\ \cline{2-3}  & MP\_800 & mechanical polishing + heat treatment\_800 \({}^{\circ}\)C \\ \cline{2-3}
**Group II** & MP\_910 & mechanical polishing + heat treatment\_910 \({}^{\circ}\)C \\ \cline{2-3}  & MP\_1020 & mechanical polishing + heat treatment\_1020 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table}
Table 2: Division of samples for testing.  
The tests were conducted on both the sandblasted and mechanically polished samples, as the type of surface preparation depends on the application of the implant. A highly developed surface is required for implants that require osseointegration, while a polished surface is required for short-term implants or those requiring low friction between components (e.g., knee joint) [2; 27].