Evaluating the Mechanical Properties of Dense Hybrid Aerosol Deposition Alumina Coatings Using the Nanoindentation Method

Hybrid aerosol deposition (HAD) is a new coating method to deposit homogeneous nanostructured ceramic coatings. It requires an accurate evaluation of the fabricated coating properties. Here, alpha-alumina (α-Al₂O₃) fine powder was sprayed using HAD. The obtained coatings were dense and uniform with a nanocrystalline structure. X-ray diffraction measurements revealed that the fabricated HAD Al₂O₃ coatings consisted mainly of α-Al₂O₃ phase. The hardness and Young modulus of the coatings were evaluated using micro-Vickers and nanoindentation methods with the Weibull distribution. The micro-Vickers hardness of HAD Al₂O₃ coatings was approximately 1400 Vickers hardness (approximately 15 GPa). The variation of mechanical properties, which were obtained using the nanoindentation method, of HAD coatings was extremely small and smaller than that of plasma-sprayed coatings. Thus, HAD coatings contained less pores and cracks than plasma-sprayed coatings.