模拟海洋环境Ti_(2)AlNb合金高温腐蚀行为研究

High-Temperature Corrosion Behaviors of Ti_(2)AlNb Alloy in Simulated Marine Environment

通过设计高温氧化试验、高温热盐腐蚀试验、高温热盐-水汽协同腐蚀试验,系统开展模拟海洋环境Ti_(2)AlNb合金的高温腐蚀行为与机理研究。利用XRD、SEM和EDS等微尺度分析表征方法,全面解析Ti_(2)AlNb合金物相结构特征、微观腐蚀形貌及腐蚀产物成分。研究结果表明,经650℃氧化400 h后,Ti_(2)AlNb合金的氧化增重仅为0.507 mg/cm^(2),表面原位生成均匀致密的氧化层,其厚度约3μm。经650℃热盐腐蚀400 h后,Ti_(2)AlNb合金增重高达4.049 mg/cm^(2),表面氧化层呈棕黄色且厚度高达150μm。热盐试验过程中混合盐共晶反应产生的Cl_(2)作为催化载体加速合金腐蚀降解,其诱导形成的气态氯化物及腐蚀产物(如NaNbO_(3)和Na_(2)TiO_(3))最终导致氧化层的严重开裂和剥落,使合金整体严重失效退化。经650℃热盐-水汽协同腐蚀400 h后,Ti_(2)AlNb合金的腐蚀损伤进一步加剧,水汽环境导致其表面氧化层腐蚀降解及HCl形成,而HCl内渗进一步加速了基体合金降解。此外,混合盐的内扩散及其共晶反应所产生的Cl_(2)会与水反应再次形成HCl,而HCl进一步加速Ti_(2)AlNb腐蚀降解进程,并导致大量疏松腐蚀产物堆积和脱落,即高温热盐-水汽强耦合效应严重威胁Ti_(2)AlNb合金的服役寿命。

In this work,high temperature oxidation tests,high temperature hot salt corrosion tests and high temperature hot salt-water vapor synergistic corrosion tests were designed and used to systematically investigate the high temperature corrosion behavior and mechanism of Ti_(2)AlNb alloy in simulated marine environments.The phase structure characteristics,microscopic corrosion morphology and corrosion product composition of Ti_(2)AlNb alloy were comprehensively characterized by XRD,SEM and EDS microscale analysis methods.Results showed that after 400 h of oxidation at 650℃,the oxidation weight gain of Ti_(2)AlNb alloy was only 0.507 mg/cm^(2),and a uniform dense oxide layer with approximately 3μm thickness was generated in situ on the surface.After 400 h of hot salt corrosion at 650℃,the weight gain of Ti_(2)AlNb alloy was as high as 4.049 mg/cm^(2),and the surface oxide layer was brownish yellow with a thickness of up to 150μm.Meanwhile,the Cl_(2) generated by the mixed salt eutectic reaction during the hot salt test served as a catalytic carrier to accelerate the corrosion degradation of the alloy,and the induced formation of gaseous chlorides and corrosion products(such as NaNbO_(3) and Na_(2)TiO_(3))ultimately led to severe cracking and peeling of the oxide layer,resulting in severe overall failure and degradation of the alloy.After 400 h of synergistic corrosion by 650℃hot salt water vapor,the corrosion damage of Ti_(2)AlNb alloy was further intensified.The water vapor environment led to the corrosion degradation of its surface oxide layer and the formation of HCl,and HCl infiltration further accelerated the degradation of the substrate alloy.In addition,the internal dif-fusion of mixed salts and the Cl_(2) produced by their eutectic reaction reacted with water to form HCl again,and HCl further accelerated the cor-rosion degradation process of Ti_(2)AlNb,which further caused the accumulation and detachment of a large number of loose corrosion products.As a result,the strong coupling effect of high-temperature hot salt water vapor seriously threatened the service life of Ti_(2)AlNb alloy.