Heat treatment on microstructure and tensile strength of 316 stainless steel by selective laser melting

The organization and tensile properties of as-deposited, 400℃/3 h annealing, 900℃/3 h annealing state and hot isostatic pressing (HIP) of 316 stainless steel by selective laser melting are studied. The results show that the deposited organization is mainly composed of columnar crystals grown epitaxially. The organization of the asdeposited sample after 400℃/3 h annealing doesn't change significantly, the transverse and longitudinal strength increase slightly and the longitudinal elongation improves significantly; the coarse columnar crystals after 900℃/3 h annealing split into more slender columnar crystals. In the case of strength reducing, the transverse and longitudinal elongation improve significantly and the tensile strength and elongation attain the forging level; after HIP, the coarse columnar crystals split into small columnar crystals and tend to equiaxial. The lateral and longitudinal strength decrease significantly, while the lateral and longitudinal elongation increase, the tensile strength and elongation attain the forging level. By comparing of the four states, the tensile strength and elongation after 900℃/3 h anneal match the best.