不同水工况下超临界机组水冷壁管材料的腐蚀特性研究

利用OM,SEM/EDS和XRD等测试手段,研究了模拟还原性全挥发处理(AVT(R))和给水加氧处理(OT)工况下Cl-及Cl-/SO42-对超临界机组水冷壁管材料15CrMoG的腐蚀特性的影响。结果表明:在AVT(R)工况下试片表面氧化物颗粒比OT工况更为均一且分布均匀;在含Cl-或Cl-/SO42-模拟OT溶液工况中,试片腐蚀程度随离子浓度增大而增大。在相同离子浓度的OT工况溶液中试片的腐蚀程度比AVT(R)更严重,且在同一工况下相同离子浓度的Cl-/SO42-比Cl-侵蚀性强。由于点蚀的自催化作用,在模拟AVT(R)和OT工况溶液中试片均会发生严重局部腐蚀。EDS结果表明,两种工况不同离子溶液中试片的点蚀坑内均未发现Cl-,但测得S的含量与水冷壁管成分相比显著增高。

Corrosion Characteristics of 15CrMoG Steel a Supercritical Unit Water-wall Tube Material in Waters ofDifferent Water Chemistry

The corrosion characteristics of 15CrMoG steel a supercritical unit water-wall tube material in two kinds of waters were studied by means of metallography, SEM/EDS, and XRD etc. The two waters aim to simulate the boiler water after the all-volatile treatment (reduction) and the oxygenated treatment, i.e. all-volative treatment (reduction) (ATV(R)) water and oxygenated treatment (OT) water respectively. The results showed that a much uniform oxide scale with much uniform particles size distribution grew on the steel surface under the AVT(R) condition rather than that under OT condition. The corrosion degree of the steel increased in the OT water with addition of Cl^- or Cl^-/SO₄^2- with increasing ion concentrations. At the same ion concentration, the corrosion of the steel under the simulated OT condition was more severe than that under AVT(R) condition and the Cl^-/SO₄^2- was more corrosive than Cl^- under the same condition. Due to autocatalytic effect of pitting corrosion, serious local corrosion occurred on the steel in the simulated AVT(R) and OT waters. It is noted that Cl^- was not detected but an obvious S content was detected by EDS in the pits on the steel surface under the two conditions with different ion in waters.