Effect of long term aging on Microstructure and precipitates of valve bolts in power plant

Abstract

Abstract 10Cr11Co3W3NiMoVNbNB is used as the materials of Intermediate Pressure Control Valve, High Pressure Control Valve, and Main Stop Valve in some thermal power plant. After 45,000 hours of operation, the mechanical properties of this those materials has have been decreased greatly. By means of scanning electron microscopy, transmission electron microscopy and thermodynamic software simulation analysis, the conclusions can be drawn: under this operation environment, the coarsening of martensite lath and the dissolution-reprecipitation of second phases such as M23C6 carbides and MX phases are the main reasons which result in the decrease both in the room mechanical properties and high temperature mechanical properties of materials.