Failure of Ceramic Coatings on Soft Substrates

A design concept for potentially hard damage-resistant ceramic coatings on relatively soft substrates is proposed. Such coating structures are of direct relevance to biomechanical structures, especially teeth and dental crowns. In this study failure modes in bilayers and trilayers with relatively hard, brittle coating outerlayers on soft, tough substrate underlayers are evaluated. Coating/substrate systems of interest include ceramic/ceramic, ceramic/metal, and ceramic/polymer. A key element of these structures is a well-bonded interface, to prevent delamination during stressing. The objective is to arrest intrusive coating cracks in a tough sublayer, rather than merely to deflect them along a weak interface.