Effect of Interlayer Dwell Time on Microstructure and Properties of ER2209 Duplex Stainless Steel Made By Plasma Arc Additive

The microstructure characteristics of different planes of ER2209 surfacing samples manufactured by plasma arc additive under different interlayer dwell times (1 min, 4 min) were studied, and the polarization curves and Nyquist diagrams of the x-z and y-z planes of the surfacing samples under different interlayer dwell times in 3.5wt%NaCl solution were tested. The electrochemical corrosion behavior of the surfacing samples on different planes was investigated. The results show that the microstructure of different regions under different interlayer dwell times is composed of ferrite phase and austenite phase, showing obvious anisotropy and inhomogeneity. Approximately hexagonal grain boundary austenite is observed on the x-y plane, and austenite grains with a certain orientation are observed on the x-z/y-z plane. The polarization curves of the x-z/y-z plane are roughly same under different interlayer dwell times, and the E_corr values of the two planes show great differences. The corrosion rate of the x-z plane is slightly higher than that of the y-z plane. Compared with the x-z plane samples, the y-z plane sample has a relatively low Q_o value and a relatively high R_p value, confirming that the stability and barrier properties of the oxide film formed on the y-z plane are improved. Compared with the interlayer residence time of 4 min, the lower E_corr value, lowerQ_ovalue and higher R_p value under the interlayer residence time of 1 min indicate better corrosion resistance of the surfacing samples.