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2934 |
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Thursday, September 29, 2011, Saal B2.2 2:50 PM Characterization & Testing 4 |
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Evaluation of young's modulus and porosity in thermally sprayed ceramic and hard metal coatings by laser acoustic surface waves (LAWave®) method |
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Maria Manuel Barbosa* / Fraunhofer Institut für Werkstoff- und Strahltechnik (IWS)
Abt. Thermische Beschichtungsverfahren, Deutschland Dieter Schneider / Fraunhofer Institute IWS, Germany Roberto Puschmann/ Fraunhofer Institute IWS, Germany Filofteia-Laura Toma/ Fraunhofer Institute IWS, Germany Lutz-Michael Berger/ Fraunhofer Institute IWS, Germany |
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Youngs modulus is not only an important parameter for the mechanical properties of thermally-sprayed coatings but also a sensitive indicator of the coatings porosity. Ceramic coatings based on Al2O3, TiO2, Al2O3-TiO2, Cr2O3, and Al2O3-MgO, were produced by APS (atmospheric plasma spraying), HVOF (High Velocity Oxy Fuel spraying) or suspension-HVOF spraying. On the other hand, WC-17Co, WC-10Co4Cr, WC-20Cr3C2-7Ni and Cr3C2-25NiCr coatings were obtained by HVOF. The Elastic Modulus was systematically studied through laser acoustic surface waves using the LAWave® device. The values were then compared with those derived from the Oliver-Pharr method using Vickers microindentations. The obtained results distinctly vary depending on the material and spraying technology. When considering an effective modulus theory it is possible to conclude that the Young modulus depends more on the morphology of the pores than on their volume fraction in the microstructure. Whereas for dense materials the results of laser-acoustic test and instrumented indentation test agree well, for most investigated ceramic coatings, the indentation test yielded values higher than those measured with laser-acoustics. Additionally to laser-acoustic laboratory tester LAWave®, a laser-acoustic hand-held probe has been applied. The measured modulus values are in agreement with the LAWave® tester. |