A material degradation study of novel FeCrAl alloys, stainless steels and nickel base alloy in fluidized bed heat exchangers of a waste-fired CFB boiler
Journal article, 2023

This study aimed to evaluate the material degradation resistance of two newly developed FeCrAl alloys exposed within the loop seal region of an 85 MWth waste-fired CFB boiler in Sweden. In addition to the FeCrAl alloys, two commercial austenitic stainless steel and one nickel base (Ni-base) alloy were also studied. The samples were exposed for 6 and 12 months by clamping half-moon rings onto tubes of the installed superheater bundle, achieving a material temperature of 500–520 °C. The material degradation of the samples was assessed by evaluating material loss using an ultrasonic thickness gauge in combination with a scanning electron microscope (SEM). Microstructural analysis was carried out using SEM coupled with Energy-dispersive X-ray spectroscopy (EDX). Both FeCrAl alloys showed promising results achieving material losses in the same range as the investigated austenitic stainless steels and the Ni-base alloy. A thin inward-growing Cr/Al-rich and thick outward-growing Fe-rich oxide were present for the FeCrAl alloys, and an internal nitridation zone was formed in the material matrix close to the metal/oxide interphase. The material loss and extent of the corrosion attack for the austenitic stainless steels varied depending on the alloy composition. However, the corrosion attack remained similar, as all the austenitic steels suffered from internal and intergranular corrosion. For the Ni-base alloy, the attack was defined by an internal Cr-rich oxide formation with no intergranular corrosion. This study suggests that the novel FeCrAl alloys provide satisfying resistance towards corrosion and erosion of the fluidized bed heat exchangers in the loop seal region of a waste-fired boiler. In addition, the stainless steel SX and the Ni-base alloy Sanicro® 69 performed well. Furthermore, the results revealed that corrosion rather than erosion was the dominating degradation process of the investigated samples, as deposit formation was observed on most of the samples as well as corrosion product layers. Thus, the erosive aspect of the attack was expected to be minor.

FeCrAl alloys

Loop seal

Austenitic alloys

Ni-base alloy

Waste-fired boiler

High-temperature corrosion


Hampus Lindmark

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Julien Phother Simon

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Maria Dolores Paz Olausson

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Johanna Nockert

Kanthal AB

Fredrik Lind

Eon SE

Anna Jonasson

Eon SE

Vesna Barisic´

Sumitomo SHI FW

Kyösti Vänskä

Sumitomo SHI FW

Laura Rioja-Monllor

Alleima AB

Jesper Liske

Chalmers, Chemistry and Chemical Engineering, Energy and Material


0016-2361 (ISSN)

Vol. 338 127299

Subject Categories

Manufacturing, Surface and Joining Technology

Metallurgy and Metallic Materials

Corrosion Engineering



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