Influence of Feedstock Powder Modification by Heat Treatments on the Properties of APS-Sprayed Al2O3-40% TiO2 Coatings
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The formation and decomposition of aluminum titanate (Al2TiO5, tialite) in feedstock powders and coatings of the binary Al2O3-TiO2 system are so far poorly understood. A commercial fused and crushed Al2O3-40%TiO2 powder was selected as the feedstock for the experimental series presented in this paper, as the composition is close to that of Al2TiO5. Part of that powder was heat-treated in air at 1150 and 1500 °C in order to modify the phase composition, while not influencing the particle size distribution and processability. The powders were analyzed by thermal analysis, XRD and FESEM including EDS of metallographically prepared cross sections. Only a maximum content of about 45 wt.% Al2TiO5 was possible to obtain with the heat treatment at 1500 °C due to inhomogeneous distribution of Al and Ti in the original powder. Coatings were prepared by plasma spraying using a TriplexPro-210 (Oerlikon Metco) with Ar-H2 and Ar-He plasma gas mixtures at plasma power levels of 41 and 48 kW. Coatings were studied by XRD, SEM including EDS linescans of metallographically prepared cross sections, and microhardness HV1. With the exception of the powder heat-treated at 1500 °C an Al2TiO5-Ti3O5 (tialite–anosovite) solid solution Al2−xTi1+xO5 instead of Al2TiO5 existed in the initial powder and the coatings.
KeywordsAl2O3-TiO2 Al2TiO5 aluminum titanate APS feedstock powder microstructure phase composition
Part of this work was funded via AiF (Project 19471 BG) by the German Federal Ministry of Economics and Technology within the framework of the program for promotion of “Industrial Joint Research” (IGF). Colleagues from Fraunhofer IKTS are thanked for execution of feedstock powder preparation by heat treatment of the powders. The support of Karl-Heinz Rauwald (FZ Jülich), who performed the spraying runs, is also gratefully acknowledged.
- 1.B. Freudenberg, Etude de la réaction à l’état solide Al2O3 + TiO2 → Al2TiO5: observation des structures: Thèse École polytechnique fédérale de Lausanne EPFL, no 709 (1987), EPFL, Lausanne, 1988Google Scholar
- 6.I.M. Low and W.K. Pang, In Situ Diffraction Study of Self-Recovery in Vacuum Decomposed Al2TiO5, J. Aust. Ceram. Soc., 2013, 49(1), p 48-52Google Scholar
- 8.R. Trache, L.-M. Berger, and C. Leyens, Comparison of Alumina-Titania Coatings Deposited by Plasma and HVOF Spray Techniques, in: Proc. Int. Thermal Spray Conf., May 21–23, 2014, Barcelona, Spain, DVS-Berichte Vol. 302, DVS Media GmbH, Düsseldorf, 2014, pp. 824-829.Google Scholar
- 10.L.-M. Berger, Tribology of Thermally Sprayed Coatings in the Al2O3-Cr2O3-TiO2 System, in: Thermal Sprayed Coatings and their Tribological Performances, IGI Global, Hershey, PA, 2015, pp. 227-267.Google Scholar
- 11.P.V. Ananthapadmanabhan, T.K. Thiyagarajan, K.P. Sreekumar, R.U. Satpute, N. Venkatramani, and K. Ramachandran, Co-spraying of Alumina-Titania: Correlation of Coating Composition and Properties with Particle Behaviour in the Plasma Jet, Surf. Coat. Technol., 2003, 168(2-3), p 231-240CrossRefGoogle Scholar
- 12.K. Niemi, Abrasion Wear Characteristics of Thermally Sprayed Alumina Based Coatings, Doctoral Thesis, Tampere University of Technology, Tampere, 2009.Google Scholar
- 15.L.-M. Berger, C.C. Stahr, F.-L. Toma, S. Saaro, M. Herrmann, D. Deska, G. Michael, and S. Thiele, Corrosion of Thermally Sprayed Oxide Ceramic Coatings (Korrosion thermisch gespritzter oxidkeramischer Schichten), Therm. Spray Bull., 2009, 2(1), p 40-56Google Scholar
- 25.L.-M. Berger, Titanium Oxide—New Opportunities for an Established Coating Material, in: Thermal Spray Solutions: Advances in Technology and Applications, Proc. Int. Thermal Spray Conf., 2004, May 10–12, Osaka, Japan, ASM International, Materials Park/OH, pp. 934-945, also DVS-Verlag, Düsseldorf, CD-ROMGoogle Scholar
- 28.H.W. Hennicke and W. Lingenberg, Formation and Decomposition of Aluminium Titanate. II. Decomposition Reaction of Aluminium Titanate, Ceram. Forum Int. (CFI), 1986, 63(3), p 100-106Google Scholar
- 29.Bruker AXS, TOPAS V4: General Profile and Structure Analysis Software for Powder Diffraction Data, 2008.Google Scholar
- 31.R. Trache, L.-M. Berger, F.-L. Toma, S. Stahr, R.S. Lima, B.R. Marple, Electrical Resistivity of Thermally Sprayed Cr2O3-TiO2 Coatings, in: Proc. Int. Thermal Spray Conf., September 27–29, 2011, Hamburg, Germany, DVS-Berichte Vol. 276, Düsseldorf, DVS-Verlag GmbH, 2011, pp. 1030-1035.Google Scholar