Mechanics in alumina ceramics modified by ultradispersed diamonds

Abstract

Alumina coating modified by ultra-dispersed diamonds (UDD) have been produced by combination of thermal flame spraying and micro arc oxidizing technologies on sprayed aluminum substrate was. Structures of alumina-based ultra dispersed diamond particles composite coatings were investigated in detail by transmission electron microscopy and SEM imaging. The particles were deposited with alumina layer on aluminum substrates under various conditions and have different levels of strength, hardness and internal stresses. It was revealed that by UDD strengthening the coating is to have high microhardness of 22 - 26 GPa, fine structure and smooth surface. Diamonds was found to be conglomerated in clusters along the interface obtained with high current density, but it disappeared when deposited with lower current regimes of alternating pulse current. On the other hand, the failure of crystal diamonds became smaller with decreasing current density concentrations. From the correspondence between the structures and the hardness of the composite, it was suggested that the effect of ultra dispersed diamonds resulted in the complicated trend of hardness, strength and fine structure with respect to current density and diamonds concentration in the electrolyte. In view of technological setup pulse current regime at high current frequency improve microhardness and roughness of the coatings. Potential application of the coating is sliding bearings, insulators, aerospace units.