Corrosion-erosion behaviour and mechanisms of in-situ transformed Cf/Al2O3 Composite

Abstract

The corrosion-erosion behaviour and mechanisms of in-situ transformed carbon fiber reinforced alumina ceramic matrix composite (Cf/Al2O3), homemade alumina (H-Al2O3) and commercial alumina (C-Al2O3) were investigated by a modified MSH tester. The both in-situ Cf/Al2O3 and H-Al2O3 were fabricated by hot-press sintering in vacuum. The corrosion-erosion experiments for the three kinds of specimens were conducted respectively in 20vol% SiC slurry of pH 2, 7 and 12 at speed of 3.67–5.76m/s for 120min. The static and dynamic soaking corrosion experiments at different pH solutions were also carried out.In the static soaking corrosion experiments, the in-situ Cf/Al2O3 exhibited better corrosive resistance than H-Al2O3 and C-Al2O3 in pH 2 acid solution, but in pH 12 alkaline solution the mass loss of three materials was very slight. The corrosion mechanism in pH 2 solution is the dissolution of bonding phase between Al2O3 particles. In corrosion-erosion tests, the corrosion-erosion loss rate of three materials increases with velocity. The corrosion-erosion loss rate of in-situ Cf/Al2O3 is less than that of C-Al2O3 in pH 2 slurry, but slight higher than that of C-Al2O3 in pH 7 and 12 slurries. The corrosion-erosion rate of in-situ Cf/Al2O3 is less than that of H-Al2O3 in all tested pH slurries. Due to the bonding phase dissolution of C-Al2O3 in pH 2 slurry, the bonding strength between Al2O3 particles weakens, which promotes the interaction between corrosion and erosion, therefore the loss rate of C-Al2O3 is higher than that of in-situ Cf/Al2O3. The effects of carbon fibers on the corrosion-erosion are absorbing the impact energy by debonding and bridging toughening mechanism and inhibiting the cracks propagating, as well as the weak interaction of corrosion and erosion, which result in the better wear resistance of the in-situ Cf/Al2O3 at pH 2.