热处理对硝酸熔盐中347H不锈钢腐蚀行为的影响

Effect of heat treatment on the corrosion behavior of 347H stainless steel in molten nitrate salt

利用静态熔盐浸泡实验,研究了不同晶粒度的347H不锈钢在565℃混合硝酸熔盐(60%NaNO_(3)+40%KNO_(3))中长达120 h的腐蚀行为.通过增重法绘制腐蚀动力学曲线,并研究347H不锈钢的表面腐蚀产物、物相、腐蚀表面微区成分,解释347H不锈钢在硝酸熔盐中的腐蚀机理.结果表明:经过固溶处理调控晶粒度的347H不锈钢在熔盐腐蚀中腐蚀速率有所降低,腐蚀动力学曲线变为线性增长趋势.通过XRD检测得到,347H不锈钢在硝酸熔盐中的腐蚀产物主要是Fe_(2)O_(3)和少量的Fe_(3)O_(4)及NaFeO 2.Fe_(3)O_(4),结构致密,能有效减小硝酸熔盐对钢基体的腐蚀,导致347H不锈钢在腐蚀后期质量损失有所降低.腐蚀产物形貌和横截面厚度分析结果表明,经过1160℃固溶处理1 h后不锈钢晶粒度达到7级时,腐蚀层厚度达到最低为0.661μm,此时347H不锈钢在硝酸熔盐中的耐腐蚀性达到最好.

In this paper,a static molten salt immersion experiment is used to study the corrosion behavior of 347H stainless steel with different grain sizes in mixed nitrate molten salt(60%NaNO_(3)+40%KNO_(3))at 565℃for up to 120 h.The corrosion kinetic curve is drawn by the weight gain method,the surface corrosion products and phases of 347H stainless steel are studied,and the micro-area composition of the corroded surface is analyzed to explain the corrosion mechanism of 347H stainless steel in nitrate molten salt.The results show that the corrosion rate of 347H stainless steel whose grain size is adjusted by solution treatment decreases during molten salt corrosion,and the corrosion kinetics curve becomes a linear growth trend.Through XRD detection,the corrosion products of 347H stainless steel in molten nitrate salt are mainly Fe_(2)O_(3)and a small amount of Fe_(3)O_(4)and NaFeO 2.Fe_(3)O_(4)has a compact structure,which can effectively reduce the corrosion of nitrate molten salt to the steel matrix,resulting in a decrease in the quality loss of 347H stainless steel in the later stage of corrosion.The results of corrosion product morphology and cross section thickness analysis show that the corrosion layer thickness of 347H stainless steel reaches the minimum of 0.661μm when the grain size of the stainless steel reaches 7 after solution treatment at 1160℃-1 h,and the corrosion resistance of 347H stainless steel in molten nitrate salt reaches the best.