Oxidation in Air at 1400 K and Optical Properties of Inconel 625, FeCrAlloy and Kanthal Super ER

Abstract

The materials used for the design of the solar receiver are one of the critical parts of the concentrated solar power (CSP) plants. An increase of the working temperature of the solar receiver could induce an increase of the efficiency of the CSP plants. Historically stainless steels were used for the solar receiver. However one limit of these materials is their poor creep resistance at high temperature. Nowadays Ni-based alloys are used, but they are limited at 1400 K by their oxidation resistance. Thus, to reach higher temperatures other materials have to be used. The alumina formers as FeCrAlloy possess a very good oxidation resistance at high temperature. The Kanthal Super ER also shows an excellent oxidation resistance. Consequently, FeCrAlloy and Kanthal Super ER were oxidized at 1373 K in air up to 48 h and compared to the currently used nickel based alloy Inconel 625. Inconel 625 shows an important mass gain followed by the spallation of its oxide scale. On the contrary, FeCrAlloy and Kanthal Super ER have a low mass gain (less than 0.40 mg cm-2) with an adherent oxide layer up to 48 h. Besides the oxidation resistance, the materials have to possess a high solar absorptivity and a total emissivity as low as possible. Oxidized Inconel 625 shows both high solar absorptivity and total emissivity. The other mentioned materials are more suitable due to their high solar absorptivity (> 0.70 for oxidized FeCrAlloy, > 0.80 for oxidized Kanthal Super ER) and their relatively low total emissivity (< 0.35 for oxidized FeCrAlloy, < 0.45 for oxidized Kanthal Super ER). Due to its high oxidation resistance and high solar absorptivity, the Kanthal Super ER seems to be the best candidate for the solar receiver application.

High-Temperature Air Stability of Electrodeposited Copper Cobalt Oxide and Copper Manganese Oxide Absorber Coatings for Concentrating Solar Power

“…However, for samples heated above 750 °C, apart from the CMO signatures, many other peaks are visible. The main Inconel 625 peaks seen in the as-prepared cases split and became multiple peaks, suggesting that the Inconel substrate degraded to many other phases and oxides of Cr, Ni, Fe, Mo, etc., as seen in the EDS spectra . Therefore, substrate oxidation, particularly above 750 °C, is relevant to these tests.…”

“…The main Inconel 625 peaks seen in the as-prepared cases split and became multiple peaks, suggesting that the Inconel substrate degraded to many other phases and oxides of Cr, Ni, Fe, Mo, etc., as seen in the EDS spectra. 54 Therefore, substrate oxidation, particularly above 750 °C, is relevant to these tests. Many researchers have also reported that above 750 °C, there is significant cation diffusion from the Inconel 625 substrate to the coating, resulting in the formation of nickel and chromium at the interfaces.…”

Oxidation and high-temperature radiative properties of the Kanthal Super ER intermetallic alloy

“…An 18 mm diameter cylinder was cut into several disks whose thicknesses range from 2 to 3 mm. These disks were polished in order to reach a quadratic surface roughness between 0.5 and 0.8 µm, with the procedure previously described [24].…”

“…Oxidation performed at 1770 K in synthetic air has shown the formation of a protective oxide scale after up to 168 h oxidation time [23]. In a previous work [24], the oxidation kinetics and room temperature optical properties of the currently used Inconel 625 have been compared to those of the alternative alloys FeCrAlloy and Kanthal Super ER (KSER) and this latest one supported 48 h oxidation at 1373 K in air inside a muffle furnace with the weakest weight change.…”

Influence of the oxidation on the optical properties of Mo-Si-Ti, Ta-Mo-Cr-Al and Ta-Mo-Cr-Ti-Al alloys

“…The maximum operating temperature of the polycrystalline nickel-based alloys currently used in the design of industrial solar receivers is approximately 800 °C when 100,000 hours of use are considered [3]. In fact, previous investigations have revealed that Inconel 625 cannot withstand more than 36 h of exposure to air at 900 °C before oxide scale spallation occurs [4].…”