The Effect of Alloying Elements on the High Temperature Oxidation of Solid-Solution Strengthened Ni-base Superalloys

AbstractThe effect of rare-earth element Y on high-temperature oxidation behavior of Cu-Si alloys at 973 and 1073 K in 0.1 MPa flowing pure O2 has been investigated. Results show at the two temperatures the mass gain of the alloys with different compositions follows the following sequence, Cu-3Si-1.0Y > Cu-3Si-0Y > Cu-3Si-0.5Y alloy. As the Y content increases, the grain size of the alloys decreases, which accelerates the diffusion rate of the alloying elements in the alloys and oxygen under the experimental conditions, increases the ratio of short-path diffusion, and promotes the formation of SiO2 and Y2O3. The three alloys do not form continuous oxide scales of SiO2 or Y2O3, but their rapid formation and dispersed distribution due to the grain-size reduction may also hinder the diffusion of alloying elements and oxygen, which is beneficial to improve the oxidation resistance of the Y-containing alloys. Thereby, the Cu-3Si-0.5Y alloy has good oxidation resistance. The Cu-3Si-1.0Y alloy exhibits largest mass gain among the three alloys, which is due to the fact that in the alloy with higher Y contend and finer grain size, more amount of Y2O3 is more quickly formed, whose mass occupy a more proportion in the whole mass gain of the alloy.

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High-Temperature Oxidation Resistance of Alumina-Forming Austenitic Stainless Steels Optimized by Refractory Metal Alloying

Metals ◽

10.3390/met11020213 ◽

2021 ◽

Vol 11 (2) ◽

pp. 213

Author(s):

Shuqi Zhang ◽

Dandan Dong ◽

Qing Wang ◽

Chuang Dong ◽

Rui Yang

Keyword(s):

High Temperature ◽

Oxidation Resistance ◽

Stainless Steels ◽

High Temperature Oxidation ◽

National Laboratory ◽

Austenitic Stainless Steels ◽

Alloying Elements ◽

Temperature Oxidation ◽

Oak Ridge ◽

Al2o3 Particles

Alumina-forming austenitic stainless steels are known for their superior high-temperature oxidation resistance. Following our previous work that solved the matching of major alloying elements in their specific 16-atom cluster formula, we here focus on the 800 °C air-oxidation resistance of 0.08 wt. % C alloy series satisfying cluster formula [(Al0.89Si0.05NbxTa0.06−x)-(Fe11.7−yNiyMn0.3)]Cr3.0−z(Mo,W)z, x = 0.03 or 0.06, y = 3.0 or 3.2, z = 0.07 or 0.2, to explore the effect of minor alloying elements Mo, Nb, Ta and W. This cluster formula is established particularly based on alloys which were originally developed by Oak Ridge National Laboratory. All samples are graded as complete oxidation resistance level according to Chinese standard HB 5258-2000, as their oxidation rate and oxidation-peeling mass are generally below 0.1 g/m2 × h and 1.0 g/m2, respectively. In alloys without Ta and W, a Cr2O3-type oxide layer is formed on the surface and Al2O3 particles of sizes up to 4 μm are distributed beneath it. In contrast, in Ta/W-containing alloys, a continuous protective Al2O3 layer is formed beneath the outer Cr2O3 layer, which prevents internal oxidation and provides the lowest weight gain. Instead of internal Al2O3 particles, AlN is formed in Ta/W-containing alloys. The W-containing alloy possesses the thinnest internal nitride zone, indicating the good inhibition effect of W on nitrogen diffusion.

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