Title: Mechanochemical wear of silicate glass: Beyond the conventional materials removal

Abstract

Understanding the friction and wear of oxide glass is of great importance for its manufacturing and operation processes. Previously, it was indicated that the friction and wear behavior of oxide glass was very sensitive to the presence of water; due to the water induced mechanochemical reactions at glass interfaces can dramatically affect wear behaviors of oxide glass. However, when the wear track is formed by the water-induced mechanochemical process, the glass structure underneath the wear track may be affected by the shear stress along the sliding direction. With various experiments and Reax-FF MD simulations, it is found that when the glass surface is scratched with stainless steel ball in liquid water, the subsurface densification underneath the wear track of glass can occur during the mechanochemical wear process even though the contact load is lower than the indentation damage threshold of the glass. This is supported by that the wear tracks becomes hallower than the pristine wear track after the subsequent sub-Tg annealing, the enhanced nano indentation hardness and modulus, enhanced dissolution in the basic solution, and the change of the subsurface Si-O-Si bond angle and Si-O bond length distributions after friction tests and subsequent annealing treatment revealed by Reax FF-MD simulations. Therefore, not only mechanochemical wear induced material removal, the friction-induced subsurface deformation can also play important roles during the wear process of oxide glass.