Amorphous phase formation of the pseudo-binary Al2O3-ZrO2 alloy during plasma spray processing

Thick deposits of the Al2O3-ZrO2 with near eutectic compositions were prepared by plasma-spray deposition and subjected to heat treatment to investigate the crystallization and phase transformation behaviors. The structures of as-sprayed deposits are mostly amorphous and a small amount of t-ZrO2 and gamma-Al2O3 particles with a diameter of approximately 20 nm are also present. Simultaneous crystallization of t-ZrO2 and gamma-Al2O3 from the glass occurs at 945 degrees C, followed by delta- and alpha-Al2O3 above 1000 degrees C, and only alpha-Al2O3 are observed above 1200 degrees C. Phase transformation of t-ZrO2 to m-ZrO2 occurs at 1213 degrees C. There is no appreciable difference in amorphous formation and subsequent crystallization and phase transformation behaviors with two different feedstock powder sizes. It is shown that it is feasible to produce the thick amorphous Al2O3-ZrO2 materials with proper control of plasma spraying process parameters. (C) 1999 Kluwer Academic Publishers.