Investigation of the impact of porosity of elements made using DMLS 3D printing technology and various printing angles on the mechanical properties and microstructure of 17-4 PH stainless steel

The research aimed to determine the impact of the degree of surface porosity of elements made using Direct Metal Laser Sintering (DMLS) 3D printing technology on the mechanical properties and structure of the elements by comparing the obtained test results with the standards and properties of elements manufactured using conventional methods. Design/methodology/approach 17-4 PH stainless steel was used to prepare the samples, from which two types of samples were printed. The elements were printed vertically and at an angle of 45° to the printer's working space. The assessment of material properties in a static tensile test was used to determine the state of stress and local strains using Digital Image Correlation. Additionally, hardness and surface roughness were measured. The structure of printed elements was also assessed using a light microscope, a scanning electron microscope and computer tomography with numerical porosity analysis. Findings The research showed a significant impact of porosity in concentrating and transferring stresses into the structure of the material, thus weakening the mechanical properties of the manufactured elements. Research limitations/implications The mechanisms of pore formation during 3D printing require in-depth analysis in various printer settings. Practical implications The mechanisms of pore formation in 3D printed metal materials affect the strength properties and, therefore, affect the applicability of the manufactured elements. Understanding the mechanisms will allow us to make corrections to technological processes. Originality/value The originality of the study lies in the link between the plastic behaviour of the material and the anisotropy of mechanical properties with the anisotropy of pore formation in elements 3D printed using DMLS technology.