Dependences of the defect, microstructure and properties of 15-5 PH martensitic stainless steel on the laser powder bed fusion process parameters

15-5 PH martensitic stainless steel is widely utilized in the marine, chemical, and aerospace industries owing to its high strength and corrosion resistance properties. The highly tailored samples can be produced via laser powder bed fusion technology, however it is still unknown how to optimize process parameter windows and conduct mechanism research for 15-5 PH steel forming. The results show that fusion defects are mostly concentrated in the region with low laser power ( P ) of 200 W, and there is no obvious distribution pattern in the pore and porosity defects. Excellent dense samples can be formed mainly at medium P of 260 W and medium scanning speed ( V ) of 1200 mm/s. The proportion of body center cubic structure reaches 91.7 % for the hatch space ( H ) of 0.06 mm, and a heterogeneous layered structure with alternating fine and coarse grain layers is formed. The sample exhibits high strength and excellent plasticity, where the ultimate tensile strength, yield strength, elongation to fracture, impact toughness, and hardness are 1161 MPa, 825 MPa, 17.5 %, 122.5 J/cm 2 , and 34.6 HRC, respectively. The excellent comprehensive property is due to fine-grained strengthening, dislocation strengthening, solid solution strengthening and intrinsic factors/oxide dispersion strengthening.