Assessing the structural and morphological effect on the tribological characteristics of boehmite and alumina sub-microparticles

Materials based on aluminium oxide can be obtained in different crystalline structures, making them suitable for several industrial applications. Chemical stability and high wear resistance are interesting peculiarities when materials undergo severe mechanical and thermal solicitations, like in breaking events, where aluminium oxides are indeed widely employed like abrasives. Controlled particles size and morphology can affect materials intrinsic properties, then representing a chance when fine adjustments in terms of specific features are required. With this in mind, we obtained boehmite and alumina sub-microparticles with different structural and morphological features by changing the synthesis parameters. The tribological properties where then investigated, using steel as counterface in pin on disc configuration. Both families can be classified as abrasive materials, but friction behaviour appears significantly different. Bohemite samples display high and stable friction coefficient, arising from a stable tribolayer formation, apart when gibbsite presence is observed, since iron hydroxide formed on the steel counterface dramatically reduces the friction stability. The behaviour of alumina family appears strongly driven by structural features, although particles shape change during the sliding tests also affects the COF value and stability.