## 1 Introduction
Desirable features for selecting the right material for the application are [22] density and porosity, particle size, conformal chemical composition, and morphological characteristics. Direct Metal Laser Sintering is mostly used for metal powders. Its characteristic feature in the process is the low laser power; the powder does not melt completely [23]. Heat treatment of the Ti6 Al4V alloy is one of the processes that enables the microstructure and mechanical properties to be adapted to the requirements of medical applications. After the 3D printing process, it enables the transformation from the martensitic \(\alpha^{\prime}\) to the more stable \(\alpha+\beta\) phases to be achieved [24]. Ti6 Al4V is a biphasic \(\alpha+\beta\) alloy, meaning that it contains two main crystalline phases: \(\alpha\) and \(\beta\). The combination of these two phases results in rarefied mechanical properties, which has led to its use particularly in the manufacture of orthopedic implants. The \(\alpha\) phase is a hexagonal (A3) closely packed structure (hcp), while the \(\beta\) phase is regularly spatially centered (bcc). Heat treatment increases the inertness of the \(\beta\) phase, resulting in a change in the mechanical properties of the alloy [25; 26]. It should be noted that the interaction of process parameters results in the formation of a regular lamellar structure and martensite decomposition. This has a significant effect on the mechanical and physical properties of the surface, which ensures that the surface of the additively manufactured implant interacts appropriately with the surrounding tissues. An important objective of the research is to verify whether traditional surface modification methods, such as sandblasting or polishing, are equally important in the case of implants manufactured using powder technology, compared to traditional manufacturing methods [4]. Therefore, the aim of this study was to determine the effect of surface modification and heat treatment on the physicochemical properties of samples produced from Ti64 ELI alloy powder using DMLS technology. In particular, the surface topography, wettability, and pitting corrosion resistance were determined to observe whether surface modification improves the physicochemical properties of the material. In addition, metallographic microscopic examinations were carried out to analyze the internal structure of the material. The results obtained will allow for the analysis of the physical and chemical properties of two groups of samples, which will make it possible to determine which surface treatment method is more advantageous. Currently, to manufacture orthopedic implants such as hip endoprostheses, a high-roughness stem is left in place for better osseointegration of the implant with the surrounding bone tissue. On the other hand, the surfaces of friction pairs (implant socket) should be characterized by low roughness in order to maintain appropriate tribological properties, as damage to friction pairs such as metal--polymer or metal-metal can lead to damage to the passive layer of the implant surface, which contributes to corrosion, e.g., pitting corrosion, the products of which, in the form of metal ions, are released into the surrounding tissues. This can lead to inflammation in the human body and even metallosis [4].