Research on corrosion behavior of 690 alloy in high temperature and high pressure water environment using EBSD technology

Abstract:

Scanning Kelvin probe (SKP) and electron backscatter diffraction（EBSD）testing techniques, combined with high temperature and pressure immersion test were used to investigate the electrochemical corrosion behavior of C-type ring made by 690 alloy with different degrees of deformation. The results show that the corrosion products on the 690 alloy are composed of oxide particles which are rich in Fe、Ni and Cr. EBSD test statistics analysis shows that the proportion of Σ3 grain boundaries in 690 alloy with 25% deformation is 10% more than that of 690 alloy with 50% deformation, and both kinds of 690 alloy have mild but different texture. The SKP measurement results display that Ekp of C-type ring samples after immersion has a significant rise, reaching -3.5mV for 690 alloy with 25% deformation and -29.2mV for 690 alloy with 50% deformation respectively, which also indicates the corrosion products film on 690 alloy with 25% deformation plays a better protective role as it results in a higher Ekp (26mV higher than that of 690 alloy with 50% deformation).

Key words:corrosion; 690 alloy; EBSD; SKP