Peculiarities of the evolution of the microstructure and mechanical properties depending on the correction of the focal length in parts made by laser melting in a powder layer

Abstract. Defects in finished products are a major factor contributing to the failure of parts produced through laser melting in a powder bed. Consequently, numerous studies have focused on controlling the laser melting process to achieve high-density parts without voids. In industrial applications, an optical system, specifically a three-axis dynamic focusing system, is commonly used to increase the printing area. However, this system requires focal length adjustments, which significantly influence the quality of the finished products, particularly in terms of the repeatability of mechanical properties based on the focal length offset from the center. Research has shown that variations in focal length correction result in deviations in the mechanical properties of the parts. Microstructural analysis revealed that focal length shifts lead to distortion of track boundaries, indicating changes in track crystallization due to the altered curvature of the focal spot.