Inconel 690TT和Incoloy 800MA蒸汽发生器管材在高温高压水中的腐蚀行为研究

CORROSION BEHAVIORS OF INCONEL 690TT AND INCOLOY 800MA STEAM GENERATOR TUBES IN HIGH TEMPERATURE HIGH PRESSURE WATER

利用多种分析手段深入分析了Inconel 690TT和Incoloy 800MA合金蒸汽发生器管材及其在高温高压水环境中的腐蚀行为.结果表明,沿管材厚度方向从内壁至外壁,Inconel 690TT合金管材S3晶界偏离理想晶界的程度逐渐增大,Kernel平均取向差（KAM）也逐渐增大,管材外壁为最薄弱区;Incoloy 800MA合金管材S3晶界偏离理想晶界的程度均匀,且主要集中于0～1°的小偏差范围内,KAM应变的变化也趋于平缓.溶氧的高温纯H2O中,Inconel 690TT合金表面腐蚀产物为双层膜结构,外层为富Fe尖晶石与NiO小颗粒,内层膜为NiO相且疏松多孔,不能对基体起到良好的保护作用,局部区域腐蚀深度可达716 nm;Incoloy 800MA合金表面腐蚀产物为双层膜结构,外层为大颗粒状尖晶石相,内层膜为小颗粒尖晶石相,Cr在内层膜与基体的界面富集,平均腐蚀深度仅约为150 nm.相同条件下,溶氧的高温纯H2O中Incoloy 800MA合金的内层膜厚度显著小于Inconel 690TT合金.因此,在溶氧高温高压纯H2O环境中,Cr发生溶解,Incoloy 800MA合金比Inconel 690TT合金耐蚀性更优.

Inconel 690 TT and Incoloy 800 MA have been widely used as steam generator heat transfer tubes in nuclear power plants（NPPs）. The corrosion behaviors of these two alloys in high temperature high pressure water have to be fully addressed. This work systematically studied the microstructures of the as- received Inconel690 TT and Incoloy 800 MA steam generator tubes（SGTs） and compared the oxide films formed on the tubing materials in high temperature water using several analytical methods including SEM, EBSD, GIXRD, SAED and STEM. The results show that from outer surface to inner surface of Inconel 690 TT SGTs, the deviation degrees from the ideal S3 misorientation and the average value of Kernel average misorientation（KAM） gradually increase. The outer surface of Inconel 690 TT SGTs are weakest. For Incoloy 800 MA SGTs, the deviation degrees from the ideal S3 misorientation are within 0～1°, and the change of KAM average value is small. Exposed to325 ℃ pure water containing 0.75×10^（-6）O2 for 720 h, oxide films of both Inconel 690 TT SGTs and Incoloy 800 MA SGTs have duplex structure. On Inconel 690 TT SGTs, the outer layer is Fe-rich spinel and small Ni O particles; the inner layer mainly is Ni O, porous and less protective with the thickness of 716 nm. On Incoloy 800 MA SGTs, the outer layer is big polyhedral spinel; the inner layer is small polyhedral spinel and protective with the average thickness of 150 nm; Cr is enriched at the interface between inner oxide layer and matrix. In high temperature water with dissolved oxygen, due to the preferential dissolution of Cr, Incoloy 800 MA is more corrosion resistant than Inconel 690 TT.