摘要
17 Cr–1 Si–0.5 Nb–1.2 Cu ferritic heat-resistant stainless steel was aged at 750 °C from 10 min to 30 h to simulate time aging and study the microstructural evolution and its effect on corrosion behavior by using optical microscopy, scanning electron microscopy, transmission electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy, and the Mott–Schottky approach. Four types of precipitates were discovered, including ε-Cu, NbC, Fe3 Nb3 C, and Fe2 Nb-type Laves phase. The nano-sized ε-Cu phase forms first, and its fraction follows the parabolic law change and is the largest. Compared to NbC and Fe3 Nb3 C particles, the coarsening of the Laves phase is the most pronounced. The aging process is divided into three parts: early-aged(0–5 h), peak-aged(5 h), and over-aged(5–30 h). However, the corrosion resistance is reduced in the early-aged stage of 0–2 h. Further extending the aging time to 30 h, the corrosion resistance is gradually improved. This change may be related to the competitive relationship between the beneficial effects of the Cu-rich phase and the harmful effects of Nb-containing particles. The dissolved Cu on the surface becomes more effective for the suppression of the anodic dissolution by the formation of ionic compounds of chlorine, thereby reducing the deterioration of corrosion resistance caused by Nb-rich precipitation.
基金
the National Natural Science Foundation of China(Nos.51604034 and 51974032)
the Science and Technology Project of Jilin Education Department in 13th Five-Year(No.JJKH20181008KJ)
the Science and Technology Development Program of Jilin Province(No.20190302003GX)。
