DZ125合金抗热腐蚀性能研究

Hot Corrosion Behavior of DZ125 Alloy in Molten Salt Environment

镍基高温合金的耐热腐蚀性能研究对提高其服役寿命具有重要意义。研究了DZ125合金在900℃下25%K2SO4+75%Na2SO4熔盐及850℃下25%NaCl+75%Na2SO4熔盐(质量分数)中的热腐蚀行为,采用扫描电子显微镜(SEM)、能谱仪(EDS)及X射线衍射仪(XRD)分析了腐蚀产物膜的结构及相组成,并探讨了其腐蚀速率和腐蚀机制。结果表明:DZ125合金在两种熔盐中的腐蚀产物膜结构疏松,容易剥落,对基体没有保护作用。在K2SO4+Na2SO4熔盐中,DZ125合金腐蚀产物膜分为两层,外层主要为Cr2O3,内层主要为Al2O3,Ni3S2和镍基固溶体,内氧化和内硫化是其失效的主要原因;在NaCl+Na2SO4熔盐中,NaCl的加入使氧化膜发生溶解,提高了S,O元素向腐蚀产物膜内部的扩散速率,因此腐蚀是氧化、硫化与氯化协同作用的结果,导致DZ125合金热腐蚀速率显著高于单纯的硫酸盐。

The study of hot corrosion of Ni-based superalloy is very important in increasing its service lifetime.In this paper,hot corrosion behavior of DZ125 alloy in molten salt environment of 25%NaCl+75%Na2 SO4 at 850℃and 25%K2 SO4+75%Na2 SO4(mass fraction)was investigated.The microstructures and phase constitution of the hot corrosion scales were analyzed by virtue of X-ray diffraction(XRD),scanning electron microscope(SEM)and energy dispersive spectrometry(EDS).Hot corrosion rate and mechanical properties were also being discussed.The results showed that the corrosion film was loose and easy to peel off,and thus had little protective effects to the substrate in both molten salts.Two corrosion layers fonned in the DZ125 alloy in K2 SO4+Na2 SO4 salt,including the outer layer consisted of Cr2 O3,inner layer consisted of Al2 O3,Ni3 S2 and Ni-base solid solution,and the DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.NaCl-induced accelerated hot corrosion because the oxide scales could partially dissolve in the melt and resulted from the diffusion of sulfur and oxygen into the corrosion film,that made hot corrosion process include synergistic effect of sulfuration,oxidation and chlorination.The hot corrosion of DZ125 alloy in molten sulfate including NaCl was much more serious and rapid than that in pure molten sulfate.