Single crystalline austenitic stainless steels based on 316L have been manufactured in order to improve their resistance against intergranular corrosion and stress corrosion cracking. However, both the 0.2% proof strength and tensile strength of the single crystals were lower than polycrystalline 316L steel. Precipitation hardening methods were used to increase mechanical strength of the single crystals. Addition of niobium followed by solution heat treatments at 1423 K and 1523 K and an aging treatment at 1073 K were required to obtain the proper intermetallic compound precipitations. The precipitates were of Laves phase which were strongly enriched in iron, molybdenum and niobium. They were in the shape of platelets, with an average diameter of 0.3 μm and a planar density of 10 μm−2. The 0.2% proof strength and room temperature tensile strength measured for an ⟨100⟩-oriented specimen with 1.0 mass% niobium were 369 MPa and 714 MPa, respectively.
