Oscillating sliding wear of cordierite glass and ceramic in liquid media

Tribological properties of amorphous and crystalline cordierite (magnesium aluminosilicate) were studied under conditions of oscillating sliding contact against Al2O3 in various liquid media. The tests were conducted using a ball-on-block tribometer at air with varied humidity and in distilled water as well as aqueous hydrochloric and caustic soda solutions with varied concentrations. Additional tests were run in air with steel and cemented carbides, respectively, as materials of the counterbody. The results showed that hardness and Young's modulus were reduced in the surface of the cordierite materials owing to reactions with the various liquid media. The influence of the acids and bases was explained by ion exchange processes and network dissolution processes, respectively. As a consequence of formation of reaction layers, the friction coefficient and amount of wear were substantially lower in hydrogen chloride or sodium hydroxide solutions than in air or distilled water. Generally, the friction coefficient tended to be smaller on cordierite polycrystal than on cordierite glass. Depending on the concentration of the acids and bases, a transition from high to low wear intensities occurred with increasing duration of testing. SEM studies showed distinct effects of the various media on features of the worn surfaces. (C) 1997 Elsevier Science S.A.