The precipitation behavior and mechanical properties of long term serviced HR3C/T92 dissimilar joint

The HR3C/T92 dissimilar joint had already served for 51020 h under 605 °C and 26.25 MPa. The microstructure and mechanical properties of the long term service HR3C/T92 dissimilar joint were tested by XRD, SEM, EPMA, TEM, the impact testing machine and the creep and stress rupture testing machine. The SEM results indicate that the precipitation behavior of long term service HR3C steel is complicated, multiple precipitates had precipitated during the service. Chain-liked M23C6 phase precipitated along the grain boundary cause the chromium depletion zone along the grain boundary. The T92 base metal precipitated lots of carbide particles during the service. The impact fracture of the HR3C base metal is brittle fracture while the impact fracture of the T92 base metal is ductile fracture. Moreover, the impact fracture of the weld is mixed fracture. The impact energy of the HR3C base metal has a drop of 90% compared to the as received HR3C metal. Chain-liked M23C6 phase along the grain boundary lead to the brittleness of the service HR3C steel. The high-temperature creep resistance of the HR3C base metal is better than that of the T92 base metal after service. The resistant to high-temperature creep of the service weld is similar to that of the service T92 base metal. With the increase of temperature, the creep resistance of the T92 base metal declines the most. On the contrary, the creep resistance of the HR3C base metal shows the minimum reduction. © 2019 Trans Tech Publications Ltd, Switzerland.