Microstructure and mechanical characteristics of laser-alloyed alumina ceramics

Commercially available alumina ceramic A124 containing 5% porosity was alloyed by adding HfO2 or mixtures of HfO2 with 5 or 10 mol% SiO2, CeO2 or cordierite glass using infrared laser radiation. Thickness of the alloyed surfaces ranged between 500 and 800 mum depending on the composition of the alloyed powders and laser parameters used. The resulting micro structures and worn surfaces were analysed by electron microscopy. As a result of the alloying, the tendency of crack formation and grain growth was substantially reduced in the Al2O3 ceramic during laser treatment. The composite layers, showing no open porosity, contained 20-40 vol.% second phases, which were homogeneously distributed at the grain boundaries of the alumina matrix. Due to alloying, average grain size, hardness and Young's modulus of the composite layers were reduced, but resistance to cracking under the mechanical action of a sliding diamond (scratch test) abrasive wearing were substantially enhanced compared with the unmodified dense alumina ceramics A123. (C) 2002 Elsevier Science B.V. All rights reserved.