High-temperature creep behavior and microstructural evolution of an 18Cr9Ni3CuNbVN austenitic stainless steel

• Creep strength of 18Cr9Ni3CuNbVN was increased by formation of Z, MX and Cu.
• The nanometer sized Z-phase and Cu precipitates were observed after creep.
• The creep-rupture life was improved by Z-phase, Nb(C, N) and Cu precipitates.
• The formation mechanism of Z-phase in austenitic steel was clearly shown

The creep properties of an 18Cr9Ni3CuNbVN austenitic stainless steel have been investigated at temperatures ranging from 923 to 1073 K and stresses from 120 to 250 MPa. The rupture lives ranged from 10 to 20,105 h. The stress dependence of the minimum creep rate obeyed a power law, with stress exponents ranging from 6 to 8.6. The activation energy was determined to be 460 to 485 kJ/mol/K. The microstructural evolution during the creep test was investigated. The V-rich Z-phase and metallic Cu precipitates began to precipitate in the middle of the creep deformation, resulting in an increase of the creep strength, while only Nb-based MX precipitates were present from the beginning of the high-temperature creep test.