Precipitation of Laves phase in a 28%Cr–4%Ni–2%Mo–Nb superferritic stainless steel

• Published in: Materials characterization 2008-05, Vol.59 (5), p.503-507
• Main Authors: de Andrade, Thiago Fontoura, Kliauga, Andrea Madeira, Plaut, Ronald Lesley, Padilha, Angelo Fernando
• Format: Article
• Language: English
• Subjects: AUSTENITE; CHEMICAL COMPOSITION; CHROMIUM ALLOYS; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; GRAIN BOUNDARIES; HEXAGONAL LATTICES; Laves phase; LAVES PHASES; MATERIALS SCIENCE; MATRIX MATERIALS; MOLYBDENUM ALLOYS; NICKEL ALLOYS; NIOBIUM ALLOYS; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; PRECIPITATION; Precipitation behavior; Sigma phase; Solidification; STAINLESS STEELS; Superferritic stainless steels; TEMPERATURE RANGE 1000-4000 K
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2007.03.006

The main objective of the present work was to study the precipitation of the Laves phase in the X1 CrNiMoNb 28 4 2 (Werkstoff-Nr. DIN 1.4575) superferritic stainless steel employing several complementary techniques of microstructural analysis. The phase that precipitated in largest quantity in the DIN 1.4575 steel was the sigma ( σ) phase. However, along grain boundaries, after aging at 850 °C, a Laves phase of the MgZn 2 type, with a hexagonal C14 crystal structure and chemical composition (Fe,Cr,Ni) 2(Nb,Mo,Si), was also identified. Growth of the Laves phase is curtailed by exhaustion of niobium of the matrix and by the presence of the sigma phase, which also precipitates in the vicinity of the grain boundaries, however in larger amounts. No chi ( χ) or austenite phases were detected in the temperature range studied.