Effect of Mo on the σ-phase precipitation behavior of super-austenitic stainless steel

The aging precipitation behavior of super-austenitic stainless steels 904L (4.32% molybdenum (Mo)), 254SMo (6.06% molybdenum) and AL-6XN (6.29% molybdenum) with different molybdenum contents at 800–900°C was investigated by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The effect of molybdenum content on the σ-phase precipitation behavior of commonly used super-austenitic stainless steel was investigated. The results show that the super-austenitic stainless steels with different molybdenum contents formed different numbers and shapes of σ phases in the isothermal aging process, and the number of σ phases of 254SMo and AL-6XN is much larger than that of 904L, and the shape of the σ phases mainly shows coarse acicularity and elongation, while the σ phases of 904L show fine granularity.