Microstructural evolution of the martensitic cast steel GX12CrMoVNbN9-1 during long-term annealing and creep |
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| Authors: | Dr.-Ing. Stefan Straub Dipl.-Ing. Peter Polcik Wiebke Besigk Professor Dr.-Ing. Wolfgang Blum Dipl.-Ing. Hermann König Dipl.-Ing. Karl Heinz Mayer |
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| Affiliation: | 1. Institut für Werkstoffwissenschaften, Lehrstuhl I, Universität Erlangen-Nürnberg, Erlangen;2. MAN Energie GmbH, TQW, Nürnberg, Germany |
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| Abstract: | The microstructure of four specimens of the martensitic cast steel GX12CrMoVNbN9-1 crept to fracture at 873 K for 220-33027 h was quantified by electron microscopy with regard to large M23C6-particles, small V- and Nb-containing particles, dislocations, pores, and oxidation layers. The laws of time-dependent coarsening of particles and strain-controlled growth of subgrains are consistent with those previously established for X20(22)CrMoV12-1. Using these data the microstructural model of deformation developed for X20(22)CrMoV12-1 can explain the creep behaviour of GX12CrMoVNbN9-1. The minimum in creep rate is related to the coarsening of particles and subgrains. At low stresses (< 140 MPa) the fraction of small slowly coarsening V- and Nb-containing particles leads to improved creep resistance. The material resists against pore formation; fracture occurs by necking. |
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