Corrosion behaviour of nanocrystallines alloy 690 at high-temperature and high-pressure in simulated PWR secondary environment

Abstract

The influence of ultrasonic surface rolling treatment (USRT) on the corrosion behaviour of nanocrystallines (NC) alloy 690 at high temperature and high pressure in simulated PWR secondary environment was performed by using Raman spectrometer, X-ray photoelectron spectrometer (XPS) and scanning electron microscopy (SEM). After USRT, the average size and the thickness of NC surface layer could reach 55 nm and 1 μm, respectively. Electrochemical measurements showed that the oxide film on the surface of NC alloy 690 was denser and more complete compared with coarse grained (CG) samples. The corrosion tests in ethanolamine (ETA) solution illustrated that the fine oxide particles were evenly distributed on the oxide film of NC alloy 690. The corrosion potential increased from −364 mV to −229 mV, while the corrosion current density dropped from 18.07 × 10−8 mm2 A cm−2 to 8.842 × 10−8 mm2 A cm−2 after USRT. By analysis, the inner layer of oxide film consisted of Cr2O3, NiFe2O4, and FeCr2O4, while Ni hydroxides formed the major part of the outermost layer of film. A growth model of oxide films on alloy 690 at high-temperature and high-pressure in stimulated PWR secondary environments was proposed and discussed.

Effect of alloying elements on aqueous corrosion of nickel‐based alloys at high temperatures: A review

“…According to the mechanism proposed by Li et al [ 33 ] for Alloy 690 oxide formation, it is Cr(OH) 3 that initially nucleates, then grows and converts to Cr 2 O 3. Chromium oxide islands then combine to form a continues Cr 2 O 3 layer which impedes further transport of Cr from the metal surface.…”

“…This observation is consistent with the earlier introduced [12,22,23] mechanism of oxide formation according to the contribution of alloying elements. Li et al [33] studied the effect of metal grain size on the oxide film formation of Alloy 690, and proposed a growth model of oxide film in simulated PWR environment. Coarse grain (CG, avg.…”

“…According to the mechanism proposed by Li et al [33] for Alloy 690 oxide formation, it is Cr(OH) 3 that initially nucleates, then grows and converts to Cr [34] studied the influence of temperature (in a range of 25-300°C) on the formation of passive films on Alloy 690 in alkaline environments. They [34] suggested oxide growth occurs via the formation of a double layer passive oxide via the same mechanism proposed by Machet et al for Alloy 690 in PWR primary coolant conditions for 325°C.…”

A study on the stress corrosion mechanism of microstructures in a heat-affected zone of high-strength steel weldment in artificial seawater

“…The potentiodynamic polarization test was used to evaluate the corrosion resistance to materials [20,21] figure 3 shows the polarization curve (a) and potentiostatic current density (b) of the simulated weld zones after heat treatment in artificial seawater. The results of the potential dynamic polarization indicate that the polarization curves of different microstructures are similar but the corrosion current densities of the samples are considerably different.…”

Effects of ultrasonic surface rolling and plasma nitriding on microstructure and properties of 690TT alloy

“…However, there are few literatures about complex surface treatment of 690TT alloy. USRT [9] is a way to achieve GNS, compared to other surface treatments such as severe shot peening (SSP) [10], laser shock shot peening (LSSP) [11,12] ultrasonic shot peening (USSP) [13], surface mechanical attrition treatment (SMAT) [14,15], and supersonic fine particles bombarding (SFPB) [16], it can significantly reduce the surface roughness while achieving better surface hardness and corrosion resistance. A schematic diagram was shown in figure 1.…”