Article ID Journal Published Year Pages File Type
1659809 Surface and Coatings Technology 2010 7 Pages PDF
Abstract
Severe cracking was found to occur in PVD titanium films on epoxy powder coatings. After all baking treatments, the epoxy coating had smooth, crack-free surfaces and the cracking of both the titanium film and the epoxy only took place as a result of physical vapour deposition. Tensile cracks were observed in the titanium film and not the compressive cracks expected from the conventional two-layered theoretical model. An alternative model has been developed for the prediction of thermal stress in a three-layered film-epoxy-substrate system. The model is consistent with the experimental trials and showed that cracking originated from thermal stresses developed in the titanium-epoxy-aluminum system due to the PVD process. Tensile instability and cracking were initiated where pores intersected the film-coating interface. The results showed that crack formation could be prevented by increasing the baking temperature to 210 °C. This critical temperature activates full crosslinking in the epoxy structure and raises its strength sufficiently to avoid tensile instability due to residual stress. Crack-free and high-gloss sputtered titanium films could therefore be produced on organic coatings. This offers the potential of a combined in-line PVD-powder coating technology as an alternative to electroplating.
Related Topics
Physical Sciences and Engineering Materials Science Nanotechnology
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