The excellent biocompatibility of titanium and its alloys used, for example, for medical devices, is associated with the properties of their surface oxide. For a better understanding of the tissue reaction in contact with the oxide layer, knowledge of the chemical and physical properties of this layer is of increasing interest. In this study, titania films were produced on cp-Ti and Ti6Al4V substrates by thermal oxidation, anodic oxidation, and by the sol-gel process. The thickness and structure of the films produced under different conditions were determined by ellipsometry, infrared spectroscopy, and X-ray diffraction measurements. The corrosion properties of these layers were investigated by current density-potential curves under physiological conditions. The oxide layers produced on cp-Ti and Ti6Al4V by thermal oxidation consist of TiO(2) in the rutile structure. For the anodized samples the structure of TiO(2) is a mixture of amorphous phase and anatase. The structure of the coatings produced by the sol-gel process for a constant annealing time depends on the annealing temperature, and with increasing temperature successively amorphous, anatase, and rutile structure is observed. Compared to the uncoated, polished substrate with a natural oxide layer, the corrosion resistance of cp-Ti and Ti6Al4V is increased for the samples with an oxide layer thickness of about 100 nm, independent of the oxidation procedure.

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A survey on theory, characteristic quantities and the experimental technique of induction thermography is given. Induction thermography is used for surface defect detection in forged parts of ferromagnetic steel at typical frequencies of 100–300 kHz. The sensitivity for crack detection is comparable to magnetic particle inspection. A hidden defect in ferritic steel with a coverage of 140 μm was detected by lowering the induction frequency down to 1500 Hz. Defects of fibres were detected in carbon fibre reinforced polymer (CFRP). Inductive excitation is complementary to flash excitation. By increasing the induction frequency up to 52 MHz, surface heating of CFRP can be realised. Cracks in silicon solar cells were detected. The crack tip is revealed with very high contrast. A new field is crack detection in railway components like rails and wheels. In rails, a larger defect could be detected from a test car moving at a speed of up to 15 km/h. A fully automated wheel testing system was built up as a demonstrator, that can detect defects with comparable sensitivity to magnetic particle testing. Standardisation of thermography has gained progress in the last years and will lead to standards on active thermography, flash excited and induction thermography in the next future