Impact of the Preliminary Surface Processing of Chromium-Coated E110 Alloy in a Hydrogen Atmosphere on Its High-Temperature Oxidation Resistance

Abstract

This study examines the effect of the preliminary plasma processing of E110 zirconium alloy in an argon–hydrogen mixture on its resistance to high-temperature oxidation in air. A high-frequency (13.56 MHz) inductively coupled plasma source is used to etch pre-oxidized E110 alloy samples in an argon–hydrogen mixture with a flow ratio of 1 : 1 for durations of 4, 8, 16, and 32 min. X-ray diffraction analysis of the samples melted in an inert medium identified the conditions for removing surface zirconium oxide without hydrogen saturation of the alloy. Chromium coatings, 5-µm thick, are applied to the plasma-treated surfaces using multicathode magnetron sputtering at a pressure of 0.2 Pa. Another group of samples undergo ion etching in an argon–hydrogen mixture at an accelerating voltage of 3 kV before the application of chromium coatings. The structural characteristics of the chromium coatings on the E110 alloy surface are analyzed using X-ray diffraction and transmission electron microscopy. The samples are oxidized in air at 1100°C with isothermal exposure for 20 and 60 min. The study establishes that etching the surface of the E110 alloy in high-frequency argon–hydrogen plasma increases the average surface roughness from 0.32 to 0.95 µm. Prolonged surface etching before coating application decreases the diffusion path length for oxygen through the coating to the alloy, thereby decreasing its resistance to high-temperature oxidation.