Aluminum titanate (Al_2TiO_5) is a congruently melting compound in the binary Al_2O_3-TiO_2 system, which decomposes below 1200℃. Its properties (e.g. thermal conductivity, CTE) differ significantly from those of Al_2O_3 and TiO_2. Thus it is of special interest to study the stability of Al_2TiO_5 in the spray process and its influence on the coating properties. A commercial fused and crushed Al_2O_3-40TiO_2 powder, which was found to be substoichiometric, was selected as the feedstock material for the experimental work, as the composition is close to stoichiometric Al_2TiO_5. Part of that powder was heat-treated in air at 1150° and 1500℃ in order to vary the phase composition, while not influencing the particle size distribution and processability. The powders were analyzed by thermal analysis, XRD and FESEM including metallographically prepared cross sections. A powder having Al_2TiO_5 as the main phase was not possible to be prepared due to inhomogeneous distribution of Al and Ti in the original powder. Plasma spraying was performed with a TriplexPro-210 (Oerlikon Metco) using Ar-H_2 and Ar-He plasma gas mixtures with 41 and 48 kW plasma power. Coatings were studied by XRD, SEM of metallographically prepared cross sections, and microhardness HV1. Moreover, the results show a clear influence of the Al_2TiO_5 content in the feedstock powder on the phase composition of the coatings.
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