Structure and Properties of Corrosion-Resistant Steels Fabricated by Selective Laser Melting

Resumo

The objects of the investigation are the powder of 12Kh18N10T stainless steel of the 20–63 μm powder and experimental samples formed based on it by selective laser melting (SLM). The powder was fabricated by argon atomization at a temperature of 1640°C and pressure of 27 bar. The particle structure is dendritic–cellular, and the cellular structure prevails with a decrease in the particle size (<35 μm), while the dendritic almost disappears. The characteristic particle size is d₅₀ = 37 μm and d₁₀₀ = 67 μm. The differential distribution is close to the Gaussian form, while asymmetry is associated with the satellite character and the presence of innumerous particles smaller than 20 μm in size. The powder fluidity is 3.27 g/s, while the apparent density is 4.41 g/cm³. The density of the samples of the 12Kh18N10T steel samples grown using a Concept Laser M2 installation under a laser power of 180 W and speed of 700 mm/s is 7.89 g/cm³ on average. Since the density of compact steel is 7.95 g/cm³, the material is rather high-density. The microstructure of the 12Kh18N10T sample is continuous, has no pores and cracks, and comprises the austenite solid solution. The average size of coherent scattering regions in the grain bulk is 19 nm. The arc-shaped interfaces of parallel semicircular tracks are formed due to the crystallization heat removal during the SLM. The elongated crystallites in the tracks are oriented inwards from the arc-shaped interface. The microhardness of the samples in the transverse plane of the metallographic section is higher than the microhardness of the planar plane. Herewith, the microhardness of the samples formed by the SLM method is higher than that of the standard compact alloy. The ultimate strength and relative elongation are 651 MPa and 47%, respectively. An increase in strength is apparently due to refining structural parameters after SLM. The fracture surface of the samples is characteristic of the clearly pronounced viscous type.