12Cr13热碱泵叶轮失效及影响因素研究

Failure Analysis of a 12Cr13 Steel Impeller in Hot Alkali Pump

12Cr13钢热碱泵使用短时间内发生严重变形失效,采用SEM、EDS、XRD等检测技术对失效后叶轮表面腐蚀形貌、腐蚀产物物相及组成进行分析,查找失效原因,采用正交实验对各因素的影响程度进行分析。结果表明:叶轮表面发生严重的冲刷腐蚀,腐蚀产物多孔疏松,分布有少量微裂纹,产物中除了可形成钝化膜的Cr_2O_3也含有Fe,Mg和Zn等的化合物,破坏了Cr2O3钝化膜的连续性和致密性,失去对基材的保护作用;大流速冲刷促进腐蚀产物的剥落,加剧局域性碱腐蚀;冲刷腐蚀造成叶轮明显减薄,降低强度,最终导致变形失效。各因素对12Cr13钢腐蚀速率影响从大到小的顺序为:流速、温度、时间、浓度。

Serious deformation induced failure occurred for a hot alkali pump made of 12Cr13 steel after a short term service. Then the damaged pump parts were analyzed by means of SEM, EDS and XRD etc. in terms of corrosion morphology, phase component and composition of corrosion products.The results revealed that serious erosion-corrosion occurred on impeller surface, and the corrosion product scale with small amount of microcracks was porous and loose,which composed of Cr2O3 as well as other compounds of Fe, Mg and Zn, the later ones destroyed the continuity and the compactness of the Cr2O3 passivation film, and thereby led to losing protectiveness. It is also found that high speed erosion promoted the spalltion of corrosion products and the probability of localized corrosion of the steel. As a result, the impeller gradually became thinner and finally led to deformation failure. The factors affected the corrosion rate of 12Cr13 steel may be ranked in a descending order as follows： flow rate, temperature,time and concentration, successively.