Towards understanding the scratchability in functional glasses

Abstract The chemical stability and transparency of functional glasses make them a suitable candidate for interactive screen displays, optical grade lenses, etc. Such applications demand glasses with increased scratch resistance to maintain their original optical and mechanical properties. For decades, indentation hardness has been used as a parameter to judge the scratch resistance of glasses. Recent technological advancements in research have shed light on the fundamental difference between the indentation hardness and scratch hardness values. Further, it is also essential to understand the fundamental behavior of glasses under various environments such as abrasive and corrosive conditions. To this extent, this review aims to provide a comprehensive overview of the experimental approaches to quantify and understand the scratch resistance of glasses. Specifically, we introduce the basic differences between indentation and scratch experiments, and various scratch quantification models available in the literature for glasses. We also discuss, in detail, the scratch experiments that have been performed on glasses and the role of various environmental conditions. Overall, through this review article, we outline the understanding on scratch behavior of glasses thus far, thereby, shedding light on the open questions which can enable the design of improved scratch-resistant glasses.