GH3625合金在75%Na_(2)SO_(4)-25%NaCl环境中热腐蚀行为研究

Study on Thermal Corrosion Behavior of GH3625 Alloy in 75%Na_(2)SO_(4)-25%NaCl Environment

将GH3625合金置于750℃下,75%Na_(2)SO_(4)-25%NaCl熔盐环境中以研究GH3625合金的热腐蚀行为,使用扫描电镜、能谱仪以及X射线衍射仪等设备对腐蚀后合金表面形貌、元素分布以及物相鉴定等进行研究分析。研究结果表明:组织为奥氏体等轴晶的GH3625合金腐蚀增重曲线呈现“两级”增重规律。合金在熔盐中腐蚀后,由腐蚀层最外层到合金基体结构依此为尖晶状NiO和片层状NiCr_(2)O_(4)、存在少许缺陷但相对致密的Cr_(2)O_(3)氧化层、带有孔洞的“蜂窝”状Ni_(2)S_(3)硫化层、基体贫Cr层以及合金基体。GH3625合金在750℃下,75%Na_(2)SO_(4)-25%NaCl熔盐环境中造成氧化膜失效的主要腐蚀反应为Cr_(2)O_(3)与Cl-以及Na_(2)O的反应,反应生成CrO_(2)Cl_(2)和NiCr_(2)O_(4)铬酸盐。

GH3625 alloy was placed in a 75%Na_(2)SO_(4)-25%NaCl molten salt environment at 750°C in order to study its thermal corrosion behavior.The scanning electron microscope,energy disperse spectroscopy,X-ray diffractometer and other equipment were used to study and analyze the surface topography,distribution of the elements and the identification of physical phase of the alloy after corrosion.The results show that the weight increase curve of GH3625 alloy with austenitic equiaxial crystal due to corrosion shows a“two-level”weight increase law.When the alloy was corroded in the molten salt,the structure from the outermost layer of the corroded layer to the alloy matrix is in turn the spinuloid NiO and lamellar NiCr_(2)O_(4),the relatively dense Cr_(2)O_(3) oxidation layer with a few defects,the“honeycomb”Ni_(2)S_(3) sulfide layer with holes,the matrix Cr-poor layer,and the alloy matrix.The main corrosion reaction that GH3625 alloy at 750℃and in 75%Na_(2)SO_(4)-25%NaCl molten salt environment caused the failure of the oxide film is the reaction of Cr_(2)O_(3) and Cl-as well as Na_(2)O,which generates CrO_(2)Cl_(2) and NiCr_(2)O_(4) chromate.