Effect of Er interlayer on microstructure, composition, electrical and mechanical properties of erbium oxide coating on steel

Abstract

The properties of a coating depend on its integrity and the interface properties between the coating and the substrate. Erbium oxide coatings with and without pre-sputtered Er interlayer were reactive sputtered and annealed at 700 °C and 900 °C to investigate the microstructure evolution in a high-temperature environment and the effect of Er interlayer on the composition, topography, microstructure, mechanical and electrical insulation properties of the coatings. X-ray diffraction (XRD) and Raman spectroscopy (Raman) showed that the presence of the Er interlayer effectively reduced the coating stress and promoted the growth of thermally stable cubic Er2O3, which may responsible for the improvement of the mechanical property of Er2O3/Er coating, and 700 °C annealed Er2O3/Er sample has the highest elastic modulus and hardness. Meanwhile, impurity was detected by XRD, Raman and energy dispersive spectroscopy (EDX) in the annealed samples, and their compositions, locations, and formation mechanism were analyzed. The presence of Er interlayer can hinder the formation of low-resistance spinel Fe–containing oxide nanocrystals, therefore, the electrical insulation performance of the composite coating did not deteriorate significantly after annealing, and still meets the requirements of ITER insulating coating.