AVS 49th International Symposium
    Surface Engineering Tuesday Sessions
       Session SE+TF-TuA

Paper SE+TF-TuA8
Nanoindentation of Alumina - Chrome Carbide and Alumina - Ultra Dispersed Diamonds nanoComposites

Tuesday, November 5, 2002, 4:20 pm, Room C-111B

Session: Systems Design of Functional Coatings
Presenter: L.V. Yerakhavets, NAMATEX System Division, Institute of Machine Reliability, Russia
Authors: L.V. Yerakhavets, NAMATEX System Division, Institute of Machine Reliability, Russia
M.V. Kireitseu, NAMATEX System Division, Institute of Machine Reliability, Russia
I.A. Nemerenco, NAMATEX System Division, Institute of Machine Reliability, Russia
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Nanoindentation experiments have been done on alumina-chrome carbide and alumina-ultra dispersed diamonds nanocomposite coating on different substrates like steel, aluminum and corundum. Films with thicknesses between 60 and 300 ?m prepared at various current intensities were indented with spherical indenters with nominal radii of 10, 50, and 150 ?m. The influence of deposition current and drying conditions were investigated using SEM. The suitability of this technique to determine morphology and the use of small spherical-tipped indenters to evaluate the mechanical properties of powder compacts was established. The revealed results may be summarized as follows: (1) The structure, grain size and morphology strongly depend on deposition current although the film density does not. At low current intensity, the grain size is found to be close to the initial particle size, whereas at higher current intensity an apparent coarser grain size occurs that, however, also contains pores and internal voids. (2) it is expected that the higher over potential results in the coarser grain size and formation of pores at higher current intensity that caused the onset of electrolysis of the aqueous medium. The localized electrolysis and oxygen evolution near the anode, resulting in a localized change in pH of the aqueous suspension, produced particle agglomeration as well as bubble formation. (3) Spherical indentation technique is found to be effectively measured contact pressure and effective elastic modulus as a function of penetration depth. The difference in contact pressure and elastic modulus vs. the indenter depth could be adjusted by the modulus vs. the ratio of the contact radius to the film thickness. The errors in the data could be also associated with radial cracks within the contact area. (4) Evidence of residual tensile stresses within the film manifested itself in the form of radial cracks from pores. The thicker films showed a greater influence of the cracks. @FootnoteText@ none