Influence of Pore Formation and Its Role on the Tensile Properties of 17-4 PH Stainless Steel Fabricated by Laser Powder Bed Fusion

Abstract

Additive manufacturing (AM) is a promising technique due to the scope of producing complex objects from a digital model, where materials are deposited in the successive layers as distinct from the conventional manufacturing approaches. In this study, laser powder bed fusion (LPBF), a class of additive manufacturing (AM), is used to make testing samples with gas atomized 17-4 PH stainless steel (SS) powder at different process parameters in argon (Ar) environment. A thorough study on powder characteristics, such as particle size distribution, powder morphology, phase formation at different atmospheres, as well as the microstructure and tensile properties of the printed parts at various energy densities were carried out. The microstructural analysis discovered the presence of columnar dendrites with complete martensite phases regardless of the process parameters. A detailed X-ray computed tomography (CT) scan analysis on printed samples explored the correlation between the pores and energy density. The sample printed with adequate energy density obtained lower porosity (volume of pores: 2 × 104 to 9 × 104 µm3, compared to 2 × 104 to 130 × 104 µm3) resulting in maximum tensile strength and elongation of 770 MPa and 38%, respectively. Therefore, it is obvious that the quantity, size and shape of pores in the printed parts significantly affect the fracture mode.