ABSTRACT
Ceramic coatings have been widely used in various engineering systems, for instance, for protecting structural materials in harsh environment, prolonging life of manufacturing tools by improving wear/corrosion resistance, and enhancing ef- ciency in energy storage and/or conversion. However, a low toughness limits the use of ceramic coatings. Most typical example is the sudden failure of machining tools with hard (H > 20 GPa) or superhard coatings (H > 40 GPa) when they are in contact with large foreign impact [1]. To solve this problem, a number of studies have been conducted to understand the origin of cracks in hard or superhard coatings [2-5]. Accordingly, several toughening methods have been developed to obtain coatings of both improved hardness and toughness [6,7]. In this chapter, we reviewed the academic journey targeting hard-yet-tough ceramic coatings in the past decades.
