Physicochemical properties of Mn1.45Co1.45Cu0.1O4 spinel coating deposited on the Crofer 22 H ferritic steel and exposed to high-temperature oxidation under thermal cycling conditions

Łukasz Mazur,Jarosław Dąbek,Michał Pyzalski,Karol Durczak,Tomasz Brylewski,Sebastian Molin

doi:10.1007/s10973-021-10884-2

Abstract

The Crofer 22 H ferritic steel substrate was coated with an Mn1.45Co1.45Cu0.1O4 spinel by means of electrophoresis. After high-temperature oxidation under thermal cycling conditions, the physicochemical properties of the obtained system were evaluated. During 48-h cycles that involved heating the samples up to temperatures of either 750 or 800 °C, the oxidation kinetics of both coated and unmodified steel approximately obeyed the parabolic rate law. The unmodified steel was oxidized at a higher rate than the system consisting of the substrate and the coating. In its bulk form, the spinel consisted entirely of the cubic phase and it exhibited high electrical conductivity. The Mn1.45Co1.45Cu0.1O4 coating, on the other hand, was compact and consisted of two phases—the cubic and the tetragonal one—and it was characterized by good adhesion to the metallic substrate. After cyclic oxidation studies conducted for the two investigated temperatures (750 or 800 °C), the coating was determined to provide a considerable improvement in the electrical properties of the Crofer 22 H ferritic steel, as demonstrated by the area-specific resistance values measured for the steel/coating system. The evaporation rate of chromium measured for these samples likewise indicates that the coating is capable of acting as an effective barrier against the formation of volatile compounds of chromium. The Mn1.45Co1.45Cu0.1O4 spinel can therefore be considered a suitable material for a coating on the Crofer 22 H ferritic steel, with intermediate-temperature solid oxide electrolyzer cells as the target application.

Highlights

Energy storage has become as important to the development of human civilization as energy generation
Measurements of the formation rate of volatile chromium compounds for the Crofer 22 H steel without any modification and after the deposition of one of two coatings—Mn1.5Co1.5O4 or Mn1.45Co1.45Cu0.1O4—in a flowing air/H2O mixture and at temperatures of either 750 or 800 °C demonstrated that these coatings may serve as barriers that effectively prevent the formation of volatile compounds of chromium
Measurements of the area-specific resistance of the layered systems obtained after long-term exposure to cyclic temperature changes revealed that the Crofer 22 H steel modified with the M n1.45Co1.45Cu0.1O4 coating was characterized by low values of this parameter above 600 and 480 °C for cyclic oxidation temperatures of 750 and 800 °C, respectively

Summary

Introduction

Energy storage has become as important to the development of human civilization as energy generation. Energy storage technologies allow surplus electrical energy to be converted into the chemical energy of fuel, which can be utilized whenever required. The principle of operation of a SOEC is the reversal of the reactions that occur in a solid oxide fuel cell (SOFC). The interconnect, which is known as a bipolar plate, is the basic structural component in both types of devices. It has a number of functions: it connects individual fuel or electrolyzer cells in series, gives the entire construction rigidity, and it supplies the gas reagents to the anode and cathode spaces via the channels located on both of its sides [9,10,11,12,13]

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Results

Conclusion