Effects of tempering and heat strengthening on hardness, indentation fracture resistance, and wear of soda lime float glass

Anecdotal and empirical evidence suggests that heat strengthening treatments compromise the wear and scratch resistance of soda lime silicate (SLS) glass. This can be problematic when trying to clean inorganic debris from the glass surface which can result in scratches degrading the optical clarity of the glass surface. Interestingly, past work using a ball-on-flat tribometer showed that SLS has peculiar wear behaviors as a function of relative humidity (RH). In dry conditions, inorganic counter surfaces abrade SLS. In contrast, in high humidity conditions, SLS substrate exhibits wear resistance for a variety of inorganic counter-surface materials. The focus of this fundamental study is to investigate the hardness, indentation fracture resistance (IFR), and wear resistance of SLS float glass with various thermal treatment histories—as-received (exposed to ambient lab air for about a year), annealed, heat strengthened, and thermally tempered—as a function of humidity using Vickers indentation and ball-on-flat tribometer. Several hypotheses were considered, and it was proposed that Si-O bond parameters, specifically strained bonds, may play an important role in the mechanochemical wear behavior of soda lime glasses at high humidity conditions.