超级双相不锈钢SAF2507焊接热模拟组织的耐点蚀性

Pitting corrosion behavior of simulated heat affected zone in SAF2507 super duplex stainless steel

采用Gleeble 3800热力模拟机对超级双相不锈钢SAF2507焊接热影响区组织进行模拟,研究了不同热输入条件下焊接热影响区显微组织和合金元素含量的变化,通过电化学循环伏安法评价了该组织的耐蚀性。研究结果表明,热输入由0.807 k J/mm增加至2.552 k J/mm时,模拟热影响区上奥氏体以晶内奥氏体、晶界奥氏体和魏氏奥氏体3种形貌析出,含量由40%增加到52%。各个热输入时奥氏体的PRE值均大于铁素体的PRE值,因此奥氏体含量的增加使热影响区组织的点蚀电位从1030 m V提高至1082 m V。但是继续增加热输入至2.965 k J/mm时,在两相交界处观察到有粒状的χ相析出。虽然该组织上奥氏体含量仍有增加,但是χ相的析出却导致组织的点蚀电位降至1065 m V。

Microstructure evolution of simulated heat affected zone in SAF2507 super duplex stainless steel under different heat input was investigated on a Gleeble3800 thermal-mechanical simulator. Pitting corrosion resistance of HAZ was measured by cyclic potentiodynamic polarization measurements. The results show that austenite content increases from 40% to 52% with the precipitation of intragraular austenite（ IGA）,grain boundary austenite（ GBA） and Widmanstatten austenite（ WA） under heat input varing from 0. 807 k J / mm to2. 552 k J / mm. The PRE value of austenite is larger than that of ferrite at the heat input. Thus,the higher austenite content led to pitting potential increasing from 1030 m V to 1082 m V. However,granular χ phase is observed at the boundary between ferrite and austenite at the heat input of 2. 965 k J / mm reduced the pitting potential to 1065 m V,even though austenite content still increased.