Microstructure Evolution of 690 TT Heat Transfer Tube Under Impact Slip Dual-Axis Fretting Corrosion in High Temperature and High Pressure Water Environment
The service water environment of high temperature and high pressure was simulated for the steam generator heat transfer tube of pressurized water reactor.690 TT alloy tube and 405 SS plate were used to form the friction pair for impact slip dual-axis fretting corrosion experiments.The microstructure evolution of 690 TT alloy tube during dual-axis impact slip fretting corrosion was investigated.White light interferometer,scanning electron microscope,transmission electron microscope,and Raman spectrum were used to investigate the microstructure and abrasive products of the abraded surface and near-surface.Results indicate that within 105 cycles,the wear mechanism of 690 TT alloy tube is mainly adhesive wear accompanied by material transfer.With the increase in cycles from 5×105 to 2×106,the wear mechanism of 690 TT alloy tube is mainly crack initiation,propagation,and delamination.In terms of microstructure evolution,mixed layer exists under the three body layer in the cross-section microstructure of samples after 105 cycles.The microstructures of samples after 5×105 and 2×106 cycles show slight difference and present a tribological transfer structure layer with thickness of about 500 nm.Additionally,the microstructure evolution enters the stable stage.
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