## 1 Introduction  
Modern techniques for the manufacturing process of machine components allow for reducing material consumption [1, 2] which leads to a reduction in waste and toxic compounds emitted into the atmosphere [3, 4]. In addition to the environmental aspect, it is also important to match the final product as closely as possible in terms of both shape and properties [5]. Therefore, the use of additive manufacturing technology (AM) for the production of machine components has recently gained importance [6]. Research on the application of this technology includes the optimization of final products in terms of the amount of material used (losses associated with the supporting structure), strength, durability as well as the reduction of defects [7, 8, 9]. One of the materials manufactured with this technology is Ti6 Al4V [10]. Ti6 Al4V alloy is widely used in the aerospace [11] and medical industries [12] because of the properties of the finished product. The main advantages of this titanium alloy include low weight and high strength, as well as corrosion resistance [13]. Research on titanium alloys is carried out for both material produced by conventional technology and additive manufacturing method (laser bed fusion--LBF). One direction of research is to apply coatings with specific properties or surface treatment to modify the top layer of the alloy [14; 15]. This results in better strength or anti-corrosion properties [16]. On the other hand, the influence of the microstructure of the Ti6 Al4V alloy material on the micro-milling process was also studied. Four different structures (bimodal, fully equiaxed, fully lamellar and mill annealed) were obtained from different heat treatments, and the microhardness of each was tested. The authors concluded that fully lamellar microstructures allow to lower cutting forces and reduce tool wear [17]. Other studies related to the machining of this alloy were connected to machining process parameters such as cutting speeds, depth of cut, and the use of cooling substances [18; 19; 20]. [PERSON] et al. [21] evaluate the influence of surface roughness, defect size and location on fatigue strength for Ti6 Al4V produced by the additive manufacturing method. Based on the study, the surface roughness of the samples has a significant effect on the initiation of surface and subsurface cracks. Similar conclusions were observed in articles [22; 23; 24] in which a correlation between fatigue cracking of Ti6 Al4V material made with additive manufacturing technology and material fracture, surface roughness and residual stresses was shown. [PERSON] et al. [25] investigated the fracture mechanism of Ti6 Al4V alloy fabricated using the laser powder bed fusion method and found that due to the LPBF process and fatigue loading, microvoids are formed, which then merge and accelerate the microcracking process. Another research direction that has not been widely disseminated at present is the evaluation of parts made with additive manufacturing technology using nondestructive testing techniques [26]. [PERSON] et al. [27] investigated the effect of defects and structure in AM 316L steel on the properties of the ultrasonic wave beam, including phase velocity. The authors of this article confirmed that the phase velocity depends on the pore geometry and crystallographic texture. In addition, it was proven that the phase velocity of the ultrasonic wave is sensitive to changes in anisotropic elastic constants. Other studies have evaluated defects in IN 625 alloy [28]. The study used the Phase array technique to detect deep, cylindrical defects in thin-walled components. The results confirmed the ability to detect cylindrical defects less than 1 mm in diameter in components with flat surfaces. It was further found that these techniques are difficult to apply to assess the condition of additively manufactured parts with a curved surface. [PERSON] et al. [29] have proven that ultrasound studies using a laser beam have fewer limitations than studies using standard techniques with a coupling agent.