In the present study, Fe-Al 2 O 3 -FeAl 2 O 4 and FeAl coatings were synthesized in situ by reactive plasma spraying of Al-Fe 2 O 3 composite powder under atmosphere and low-pressure conditions. Coating microstructure and phase composition are examined and coating formation mechanisms are discussed. It was found that FeAl 2 O 4 hercynite phase is always synthesized as an intermediate product under low oxygen partial pressure conditions. In the APS process, such a phase can be retained in the final coating by extremely fast cooling. It can also be continuously reduced to FeAl by deoxidation in an oxygen-free H/H 2 atmosphere.

Yttria-stabilized zirconia coatings were deposited onto a Ti-6Al-4V substrate through a microplasma spray technique and incubated in simulated body fluid (SBF) for different periods of time (3, 7, 14, 28 days). The formation of apatite on the surface was investigated to evaluate the bioactivity of the coatings. Surface morphologies and structural changes in the coatings before and after immersion were analyzed by optical microscopy, scanning electron microscopy, and x-ray diffractometry. The calcium (Ca 2+ ) concentration in the solutions was measured directly after the samples were removed, using an inductively coupled plasma atomic emission spectrometer (ICP). The results showed that yttria-stabilized zirconia coatings can be produced by microplasma spraying and, even though the coatings contain few small unmelted particles, apatite can be formed on the coatings that are soaked in SBF solution. These results indicate that the yttria-stabilized zirconia coatings exhibited definite bioactivity.