As-deposited amorphous or γ phase aluminium oxide coatings on iridium-coated isotropic graphite substrate were transformed into α-Al2O3 coatings after annealing at 2073 K in Ar atmosphere. Annealing also induces very small porosities, growth and coarsening of grain in α-Al2O3 coatings. The reaction between aluminium oxide and iridium coatings resulted in the formation of thin layer of AIIr compound at the interface. The thickness of AIIr interfacial compound increases with time and temperature. Furthermore, annealed specimens exhibited good strain tolerance by not allowing cracking or spalling of the coatings and good adhesion with the substrate remained.
ASJC Scopus subject areas
- Metals and Alloys