Features of the Recovery Process of Austenitic Stainless Steel Obtained by Selective Laser Melting

The microstructure and microhardness of 316L-type austenitic stainless steel obtained by selective laser melting and then annealed at 900–1200°C have been studied. This paper is aimed at clarifying the features of the recovery process in the steel. The experimental samples were developed by selective laser melting using a ProX200 3D system in a nitrogen atmosphere without platform preheating. The laser power of 240 W, the beam speed of 1070 mm/s, the distance between tracks of 80 μm, and the layer thickness of 30 μm were applied. Annealing was carried out at temperatures of 900–1200°C for 1 h and at temperatures of 1000 and 1100°C for 1 to 10 h. It was found that the recovery processes at temperatures of 900–1100°C developed with a very sluggish kinetics. After 1 h annealing at 900–1100°C, the steel microstructure steel was characterized by a grain size of 25 ± 1 µm, and a dislocation density of 8.7 × 10¹³ m^–2. An increase in the annealing duration to 10 h did not lead to significant changes in the microstructure of the steel samples annealed at 1000°C, whereas the samples annealed at 1100°C experienced the developmen of primary recrystallization resulting in twofold decrease in the dislocation density. The development of recovery in the present steel during annealing at temperatures of 900–1100°C could be expressed by Arrhenius-type relationship with a quite low activation energy of about 10 kJ/mol.