Influence of oxide films on primary water stress corrosion cracking initiation of alloy 600

Abstract

In the present study alloy 600 was tested in simulated pressurised water reactor (PWR) primary water, at 360°C, under an hydrogen partial pressure of 30 kPa. These testing conditions correspond to the maximum sensitivity of alloy 600 to crack initiation. The resulting oxidised structures (corrosion scale and underlying metal) were characterised. A chromium rich oxide layer was revealed, the underlying metal being chromium depleted. In addition, analysis of the chemical composition of the metal close to the oxide scale had allowed to detect oxygen under the oxide scale and particularly in a triple grain boundary. Implication of such a finding on the crack initiation of alloy 600 is discussed. Significant diminution of the crack initiation time was observed for sample oxidised before stress corrosion tests. In view of these results, a mechanism for stress corrosion crack initiation of alloy 600 in PWR primary water was proposed.

Evaluation of Primary Water Stress Corrosion Cracking Resistance of Three Heats of Alloy 600 in 400 °C Hydrogenated Steam Condition

“…However, blocky oxides of about 100 nm were found on the surface of 'Rod', while fine platelet oxides were found for 'Tube' and 'Plate'. It has been reported that the blocky oxides are Ni-Fe spinel oxides formed on top of Cr-rich oxide layer [22]. The presence of blocky oxides for 'Rod' could be correlated with the relatively poor protection of underlying Cr-rich oxide layer as they are known to be formed by Ni-Fe diffusion through the oxide layer [23].…”

Corrosion Behavior of Alloy C‐276 in Supercritical Water

“…As a kind of nickel-base alloys, Alloy C-276 has high mechanical strength and superior toughness in high temperature [19][20][21][22]. Besides, it is observed to have an excellent high-temperature corrosion resistance.…”

Influence of dissolved oxygen concentration on the oxide film formed on Alloy 690 in high temperature water

“…The oxidation behavior of nickel-base alloys has been one of the hot topics because the oxide films formed are important to their performance. Up to now, in order to elucidate the oxidation process, some studies have been done to analyze the formed oxide films [2][3][4][5][6][7][8][9]. And the effects of different water chemistry parameters such as dissolved hydrogen (DH) [10][11][12][13][14], pH [15,16], temperature [15,17,18], Li concentration [19] and Zn injection [20,21] on the oxidation behaviors of Ni-base alloys have also been investigated.…”