Vickers Microindentation and Statistical Analysis of Microhardness of Detonation Sprayed Nanocomposite Al2O3-TiO2 Coatings

Abstract

The mechanical behaviors of detonation sprayed Al2O3/3 wt%TiO2nanocomposite and conventional microcomposite coatings are evaluated by Vickers microhardness. The distribution of microhardness values of the coatings are analyzed by Weibull statistics. The pores of the nanocomposite coating (NCC) generally appear to be of equal size and show a very homogeneous distribution, while the conventional microcomposite coating (MCC) appears as an inhomogeneous pore distribution. The results also indicate that the NCC has a better chimerism between splat interfaces than the MCC and a more homogeneous melting condition. The Al2O3phase in the NCC is evidently refined. The indentation analysis illustrates anisotropic toughness of the as-sprayed coatings, the cracks are parallel to the substrate. The NCC has a higher fracture toughness than the MCC. The NCC and MCC demonstrate a bimodal distribution. The mean microhardness value (1139.5HV100) of the NCC is higher by 15.3% than that (988.3HV100) of MCC. Less scatters are seen in the characteristic microhardness value in both low values and extremely low value of NCC than those of MCC. The excellent mechanical properties are due to the reinforcing effect of TiO2nanoparticles on the Al2O3matrix particles of NCC.