Investigation of Plasma Gradient Coatings with a Top Hafnium-Oxide Layer by Nuclear Backscattering Spectrometry

• Published in: Surface investigation, x-ray, synchrotron and neutron techniques Vol. 13; no. 3; pp. 488 - 492
• Main Authors: Savushkina, S. V., Polyansky, M. N., Tkachenko, N. V., Borisov, A. M., Kamenskih, A. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.05.2019; Springer Nature B.V
• Subjects: Backscattering; Chemistry and Materials Science; Coatings; Hafnium oxide; Low pressure; Materials Science; Porosity; Scanning electron microscopy; Scientific imaging; Sintering (powder metallurgy); Spectrometry; Spectroscopy; Spraying; Surfaces and Interfaces; Thickness; Thin Films; Yttrium oxide; Zirconium dioxide; hafnium oxide; gradient coating; nuclear backscattering spectrometry; zirconium oxide; plasma spraying
• ISSN: 1027-4510; 1819-7094
• DOI: 10.1134/S1027451019030315

Gradient coatings with a thickness up to 160 μm are obtained by the low pressure plasma spraying of NiCoCrAlY, ZrO 2 –Y 2 O 3 (7%), and HfO 2 –Y 2 O 3 (9%) powders and their mixtures. The coatings are studied by scanning electron microscopy and nuclear backscattering spectrometry of protons. According to the spectrometry data, the thickness of the gradient coatings (so-called “mass” thickness) is significantly less than the geometric thickness. It indicates a rather high porosity of the coatings (20–30%) and is explained by the presence of nanostructured areas in them. The difference between the geometric and mass layer thicknesses is less significant in the case of a thicker coating due to sintering of the particles during the spraying of subsequent upper layers. The mass thicknesses of the NiCoCrAlY + ZrO 2 –Y 2 O 3 (7%) and ZrO 2 –Y 2 O 3 (7%) + HfO 2 –Y 2 O 3 (9%) layers are greater than the thicknesses of the main layers due to the formation of additional transition zones of mixed composition at the interfaces. The NiCoCrAlY + ZrO 2 –Y 2 O 3 (7%) layer is thicker than the ZrO 2 –Y 2 O 3 (7%) + HfO 2 –Y 2 O 3 (9%) layer due to the higher porosity of the ceramic layer.