Abstract: This paper researched the microstructrue and nanoindentation mechanical properties of detonation sprayed coatings derived from Al₂O₃/TiO₂ nanocomposite powders. The pores of the
nanocomposite coating (NCC) appeared to be generally equal-sized and showed a very homogeneous distribution, while the conventional microcomposite coating (MCC) appears an inhomogeneous pore
distribution. The results also indicate that NCC has better chimerism between splat interfaces than MCC and more homogeneous melting condition. A mass of grain boundaries, sub-boundaries and
nanosized microcracks in NCC lead the matrix Al₂O₃ to be nanoparticulate, while a mass of unmelted particles can be detected in MCC. Both of Al₂O₃/3wt%TiO₂ nanocompsite and
conventional coatings exihibit apparently anisotropic nanoindentation mechanical behaviors, which are due to the anisotropic microstructure of the as-sprayed coatings. The mean values and distribution
intervals of both nanoindentation hardness and Young’s modulus of NCC are higher than those of corresponding surface and cross section of MCC. Therefore, NCC exhibits better nanoindentation
mechanical properties than MCC, which is due to the reinforcing effect of TiO₂ nanoparticles on the matrix Al₂O₃ particles of NCC.

Key words: nanocomposite coating, detonation spray, microstructure, nanoindentation mechanical properties