High-Temperature Corrosion Behaviors of Ti₂AlNb Alloy in Simulated Marine Environment

Abstract

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 Ti2AlNb alloy in simulated marine environments. The phase structure characteristics, microscopic corrosion morphology and corrosion product composition of Ti2AlNb 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 Ti2AlNb alloy was only 0.507 mg/cm2, and a uniform dense oxide layer with approximately 3 μm thickness was generated in situ on the surface. After 400 h of hot salt corrosion at 650 ℃, the weight gain of Ti2AlNb alloy was as high as 4.049 mg/cm2, and the surface oxide layer was brownish yellow with a thickness of up to 150 μm. Meanwhile, the Cl2 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 NaNbO3 and Na2TiO3) 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 Ti2AlNb 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 diffusion of mixed salts and the Cl2 produced by their eutectic reaction reacted with water to form HCl again, and HCl further accelerated the corrosion degradation process of Ti2AlNb, 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 Ti2AlNb alloy.

Keywords

• ti₂alnb alloy; high temperature oxidation; high temperature hot salt corrosion; high temperature hot salt - water vapor synergistic corrosion; corrosion and degradation mechanism