In this research, we studied the influence of process parameters on the quality of selective laser melting of 18Ni300 maraging steel. The effects of laser power and scanning speed on the relative density and hardness of 18Ni300 were studied by single-factor experiment and the orthogonal experimental method. The relative optimal process parameters of 18Ni300 were obtained when the layer thickness was 0.03 mm, and the hatch space was 0.1 mm. The microstructures and mechanical properties of the samples formed under different process parameters were characterized. The results showed that the optimal hardness and relative density of the sample were 44.7 HRC and 99.98% when the laser power was 230 W and the scanning speed was 1100 mm/s, respectively; the microstructure of the material was uniform and dense, exhibiting few pores. Some columnar crystals appeared along the boundary of the molten pool due to vertical epitaxial growth. The orientation of fine grains at the boundary of the molten pool was random, and some coarse columnar crystals in the molten pool exhibited a certain orientational preference along the orientation. In the case of optimal process parameters, the SLM-formed 18Ni300 was composed of 99.5% martensite and 0.5% retained austenite; the indentation hardness was distributed in the range of 3.2–5 GPa. The indentation modulus was between 142.8–223.4 GPa, exhibiting stronger fluctuations than the indentation hardness. The sample’s mechanical properties showed obvious anisotropy, while the tensile fracture characteristics exhibited necking. The tensile fracture morphology was ductile, and large equiaxed dimples and holes could be observed in the fiber area, accompanied by tearing characteristics.

The optimal SLM conditions of 304L stainless steel were obtained by single factor and orthogonal tests. Results indicated that the optimal hardness (75 HRB) and Relative Density (RD 99.24%) could be obtained when the laser output power was 190 W, the scanning distance was 0.09 mm and the scanning speed was 800 mm/s. The microstructure of fish scales was uniform and compact with a few pores in the optimal sample. The fine particles were randomly distributed near the edge of the molten pool, and some preferred granular columnar crystal structures were formed. Abundant entanglement dislocations were observed between cell structures, forming dislocation clusters. Spherical nano-precipitates, rich in Si, Mn, and O, were also observed near cell structures. The mechanical properties of the specimens were highly anisotropic, and there were obvious necking and ductility at the tensile fracture.

This study explores the relationship between the microstructure, composition, orientation, and mechanical properties of the nickel-based superalloy Inconel 718. Employing scanning electron microscopy (SEM), electron microprobe (EMP), nano-indentation, and other techniques, the study observes the structure, confirms the composition, determines orientation, and tests mechanical properties in specific micro-zones. Findings reveal a uniform grain distribution in Inconel 718, with a minor δ-phase presence at grain boundaries. There is a notable enrichment of Nb at the grain boundaries, whereas Fe and Cr levels are lower at these boundaries compared to the grain interiors. The indentation hardness and modulus at the grain boundaries are markedly higher than those within the grains. Moreover, grains with different orientations exhibit diverse microscale mechanical properties, such as hardness and elastic modulus. This research establishes a quantitative characterization and mapping relationship between the microstructure, composition, orientation, and mechanical properties of Inconel 718, providing a foundation for future multiscale (micro to macro) mechanical property investigations.

Automotive reinforced inner plate is a typical sheet metal stamping parts, which is characterized by complex shape, the need for multi-channel process to complete. If the parts can be based on the needs and possibilities of a reasonable combination of some processes, not only can improve the quality of the workpiece, but also can save mold costs and improve production efficiency. The finite element analysis software Dy naform is used to develop the finite element model, and the forming process of the automotive reinforced inner plate was simulated and analyzed. The process parameters influencing the forming quality were optimized, and the shape and size of the blank were optimized to obtain the ideal billet state. In the wrinkled surface on the local optimization, a good control of the product forming quality. Finally, the simulation results are compared with those of the actual production. The correctness of the numerical simulation is verified.