Stainless steel 316L prepared by laser melting consisted of hierarchical austenitic microstructure with micron sized (10-25 µm) grains containing fine 1µm subgrains with a cellular structure. At high temperature thermal treatments (≥ 1100 °C), merging and growth of the 1 µm subgrains into bigger subgrains restricted the rapid grain growth and microstructure coarsening. Partial phase transformation of austenite to ferrite at temperatures ≥ 1100 °C in combination with gradual and steady growth of subgrains inside the micron sized grains and nucleation of sigma phase have promoted the tensile strength of stainless steel 316L to 300 MPa at 1100 °C compared to conventionally made 316L counterparts with tensile strength of approximately 40 MPa. The grain growth mechanism of laser melted microstructure can change the application criteria for 316L and expand the application fields for 316L.