In order to clarify the crack morphology in 180° bend-forming of the TiN film deposited on (011) [100] single crystals of silicon steel, TiN coating by the hollow cathode discharge (HCD) method was done on a polished (011) [100] single crystal sample. The TiN-coated samples were 180° bend-formed and observed by the scanning electron microscope.
In the position (a) just above 180° bend-forming, TiN film showed the straight crack at the interval of 2-4 μm parallel to the direction of [121]
TiN. In contrast, in the position (b) near the transition zone from bend-forming to tensioning, TiN film showed an elliptical morphology 23-30 μm long and 9-12 μm wide.
The point of origin of a small TiN crack can be seen near the center of the ellipse, and the straight crack in the TiN film will propagate from this origin.
It should be noted that the TiN crack morphology differed remarkably depending on the positions of bend-forming.
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