High temperature oxidation of Cr-ZrO2-Al2O3 composite fabricated by mechanical alloying and spark plasma sintering

Abstract

The high temperature oxidation resistance of Cr-ZrO2-Al2O3 Composites fabricated by mechanical alloying and spark plasma sintering (SPS) has been evaluated. Composite powders were prepared by ball milling Cr-5vol\%ZrO2-50vol\%Al2O3 powder mixtures. Powders were compacted by SPS in less than 5 min, so that a particular metal-ceramic interpenetrating network is obtained. High temperature oxidation tests (900-1100 degrees C) in air have revealed good oxidation resistance (1.8, 2.6 and 15.3 mg/cm(2) at 900, 1000 and 1100 degrees C, respectively) due to a protective Cr2O3 layer. EDX analysis revealed that Cr diffusion takes place at 1100 degrees C from the bulk towards the composite surface leading to Cr depletion at near-surface zones. Chromium contained in the bulk tends to oxidize through oxygen diffusion apparently occurring along the grain boundaries.