OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 2 2024 X-ray diffraction analysis was conducted in the Bruker D8 Advance diffractometer with Bragg-Brentano focusing scheme in Cu Kα radiation in the range of diffraction angles 2θ = 30°–100° with a step of Δ2θ = 0.07° and exposure time of 2 seconds per point. The tube voltage was 40 kV, and the tube current was 35 mA. A semiconductor multichannel detector was used, with a 2 mm slit and Soller slit installed on the tube, and only a Soller slit on the detector. During the data collection, the specimens were rotated at a speed of 60 rpm. The spectrum processing was conducted using Diffrac.Eva and Diffrac.Topas software. For X-ray phase analysis, the specimens were electropolished on a Struers LectroPol-5 in A2 electrolyte (78 mL HClO4, 90 mL distilled water, 730 mL C2H6O, 100 mL C6H14O2) for 15 min at 10 V. Results and discussion According to metallographic analysis, the tracks obtained under all experimental modes (Table 2) are free from cracks, exhibit minimal porosity, and have defect-free boundaries with the substrate material (Fig. 2). A heat affected zone (HAZ) with a width of approximately 0.50 ± 0.05 mm is observed at the track boundary. Analysis the dependence of the track shape coefficient f on power revealed that at a scanning speed of 600 mm/min, the coefficient f exceeds the permissible range (Figure 3). The geometric parameters of the track obtained at scanning speeds of 800 and 1.00 mm/min meet the requirements for the shape coefficient, bead width, and melting coefficient of the track. The angle at the base of the track is less than 90 degrees for almost all experimental laser deposition modes. a b c Fig. 3. Dependences of the track width (a), penetration ratio (b), track shape factor (c) on the laser power (green area – range of accepted values) Microhardness of the tracks manufactured under different modes varies in the range from 386 to 499 HV (Fig. 4). From the graphs, it is evident that increasing the laser power P results in an increase in hardness, while increasing the scanning speed also results in hardness growth, although this effect is minor. It is known that during the LENS process, the material cooling rate is relatively high, which may lead to the formation of a dispersed (α + β) structure and the martensite formation. It can be assumed that the increase in hardness at high laser power is associated with an increase in the temperature gradient. Based on the track analysis, seven LENS modes were selected (Table 4). The structures of the grown monolayers are presented in Figure 5. A compliance assessment of the monolayers with the specified criteria is shown in the graphs in Figure 6. The manufacturing mode with a distance of 0.9L between adjacent tracks is considered impractical as height variation in some modes is close to 90 %. These specimens consisted not of monolithic layers but of a set of individual tracks. Specimens with a track spacing of 0.5L and 0.7L have approximately the same geometry. The height variation in both cases differs slightly and ranges from 10 to 20 %. It should be noted that at a spacing of 0.5L, the layer height was smaller for all LENS modes compared to 0.7L (Fig. 6, b). This is likely due to the
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