Oxidation of two three-phase Cu–30Ni–Cr alloys at 700–800°C in 1atm of pure oxygen

Oxidation of a quaternary two-phase Cu–40Ni–17.5Cr–2.5Al alloy at 973–1073K in 101kPa O2

“…Thus, a Cr content of 17.5 at.% is likely to produce a selective oxidation of the reactive component Cr over the quaternary two-phase Cu-40Ni-17.5Cr-2.5Al alloy surface. The critical Cr content required to form the selective external oxidation over quaternary two-phase Cu-Ni-Cr-Al alloy surface is rather lower than those over ternary two-phase and three-phase Cu-Ni-Cr alloy, or many binary twophase alloy surface [8][9][10][11][12][16][17][18][19].…”

“…The previous studies of Cu-Ni-Cr alloys showed that a single-phase alloy with about 20 at.% Cr is able to form an external scale of chromia over the alloy surface, while a two-phase alloy with about 20 at.% Cr is unable to form an external scale of chromia, but is able to form a thin and very irregularly continuous layer of chromia at the top of the mixed internal oxidation region with a gradual decrease in the oxidation rate up to very low values [8]. A three-phase alloy with about 20 at.% Cr is unable to form a chromia scale over the alloy surface and at the base of the scale even after an extended period of oxidation [9], while a threephase alloy with about 30 at.% Cr is able to form a very irregular layer of chromia at the top of the mixed internal oxidation region or an external scale of chromia with an internal oxidation of Cr [10,11]. * Corresponding author.…”

“…: +86 24 86593317; fax: +86 24 86592548. Finally, a three-phase alloy with about 40 at.% Cr is only able to form an external scale of chromia [11]. Compared with the corresponding binary two-phase Cu-Cr alloys [12], it is found that adding the third component Ni to Cu-Cr alloys is able to decrease the critical content of the reactive component Cr required to form an exclusive external scale of chromia over alloy surface evidently, but it is still higher than that for binary single-phase alloys such as Ni-Cr alloys, etc.…”

High-Temperature Oxidation Behavior of Cu-20Ni-75Co Alloy

“…Usually, the formation of the oxide scales of the most reactive component such as Cr 2 O 3 , Al 2 O 3 , or SiO 2 on the alloy surface is able to prevent the alloys from being oxidizing at high temperatures [1][2][3]. The alloys are able to form the continuous scales of Cr 2 O 3 , Al 2 O 3 , or SiO 2 only if the content of the most reactive component Cr, Al or Si exceeds a critical content [4][5][6]. The previous studies have proved that the continuous and protective external oxide scales of the more reactive component for binary two-phase alloys is very difficult to form and required a very high critical content of the most reactive component as compared with binary single-phase alloys under the same values of all the parameters involved because of two phases in equilibrium and the very low solubility of two components [7][8][9][10][11].…”