OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 2 2024 Ta b l e 3 Geometric parameters of a single laser track evaluation criteria Parameter Valid value Shape factor (f) 0.2…0.33 Penetration ratio (d) 0.1…0.4 Track width (L) 1.7…3.0 mm Angle at the base (q) < 90° Fig. 2. Shape of the track formed by a laser power of 1.000 W and laser scanning speed of 1.000 mm/min – melting coefficient d p p h S d S S = + , where Sp and Sh are the areas of the track below and above the substrate surface; – track width L; – angle at the base of the track θ [15, 16–19]. The acceptable values of these characteristics are provided in Table 3. Additionally, the absence of cracks is one of the important criteria. During the formation of monolayers, the distance between adjacent tracks varied in the range from 0.5L to 0.9L, where L is the width of the track determined in the previous step. The requirements for the geometric parameters of the mono-layers were as follows: the height variation of the mono-layer should not exceed 30 % of its maximum height, and the depth of melting should be less than 2/3 of the layer height. For volumetric specimens manufactured under different technological modes, the presence of cracks and large (more than 1–2 µm) pores in longitudinal and transverse sections was monitored. The microstructure of the manufactured specimens was investigated using an inverted metallographic microscope Olympus GX-51. For optical metallography, the specimens were embedded in resin using an automatic press Struers CitoPress-20 and prepared on a grinding-polishing station Struers Tegramin 25. Chemical etching in a aqueous solution of hydrofluoric and nitric acids was used to reveal the structure: 3 ml HF, 15 ml HNO3, 82 ml H2O. The microhardness of the specimens was evaluated using the Vickers method on a microhardness tester Pruftechnik KB50 SR. The indentation load was 1.9 N (200 g), with a measurement error of no more than 10 %.
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