Mechanochemical Wear of Soda Lime Silica Glass in Humid Environments

Abstract

The mechanochemical wear of multicomponent glasses was studied under controlled humidity conditions using a reciprocating ball-on-flat tribometer. For dry conditions, the surfaces were extensively damaged by scratching for all of the glasses, while for humid conditions the wear behavior varied with the glass composition suggesting a chemical effect on scratch behaviors of glass surfaces. The wear of soda lime silica (also called sodium calcium silicate) glass was suppressed with increasing humidity, while the borosilicate and barium boroaluminosilicate glasses showed an increase in wear volume with increasing humidity. The unique humidity dependence of the observed mechanochemical wear of soda lime silica glass supports the hypothesis that hydronium ion formation in the sodium-leached sites of the soda lime glass enhances its wear resistance.

Effects of humidity and counter-surface on tribochemical wear of soda-lime-silica glass

“…Thus, it was believed the wear of glass in humid environments occurs through a mechanochemical process rather than a purely mechanical one. Besides, the wear resistance of soda-lime glass increased as environmental humidity increased, which was not observed for other glasses such as fused silica, borosilicate, and aluminosilicate glasses [18,19]. These results indicated that the water reactivity inside the wear track of the soda-lime glass substrate being rubbed with silica or borosilicate glass balls is quite different from other glasses.…”

“…A contact load of 0.2 N was used for all data shown in this paper. In our previous study, it was found that the glass surface is damaged at this load condition as long as detrimental tribochemical reactions are prevented by the adsorption of one monolayer of alcohol [18]. For a silicon nitride ball compressing a soda-lime-silica glass surface, the corresponding maximum Hertzian contact pressure was estimated to be 400 MPa.…”

“…Tribochemical or mechanochemical reactions are ubiquitous at sliding interfaces of various materials in humid environment [13,14,18,25]. For glass materials, stress-enhanced hydrolysis has been considered as the major reason, because the tensile stress can facilitate hydrolysis of the Si-O-Si network.…”

“…When water molecules were adsorbed at the glass surface in humid environments, the wear track of glass became smooth with much lower wear width and depth. When a thin layer of adsorbed alcohol molecules was maintained by adsorption from the gas phase, no visual wear of the glass substrates was observed at the same mechanical load and sliding speed conditions [18]. Although it was not directly measured, the adsorbed alcohol layer thickness was expected to be around one monolayer in the friction test condition since the alcohol adsorption behavior on glass would be similar to that on the silica surface [20,21].…”

“…These reports suggest that the chemical reactivity of counter-surfaces play important roles in the mechanochemical wear of sliding interfaces. Previous investigations on environmental effects reported that the friction and wear behaviors of multicomponent silicate glass substrates tested with silica and borosilicate glass balls vary drastically with humidity [17][18][19]. In dry conditions, glass substrates were easily scratched creating a very rough and deep wear track.…”