Effects of Grain Size and Humidity on Fretting Wear in Fine‐Grained Alumina, Al₂O₃/TiC, and Zirconia

Abstract

Friction and wear of sintered alumina with grain sizes between 0.4 and 3 μm were measured in comparison with Al2O3/TiC composites and with tetragonal ZrO2(3 mol% Y2O3). The dependence on the grain boundary toughness and residual microstresses is investigated, and a hierarchical order of influencing parameters is observed. In air, reduced alumina grain sizes improve the micromechanical stability of the grain boundaries and the hardness, and reduced wear is governed by microplastic deformation, with few pullout events. Humidity and water slightly reduce the friction of all of the investigated ceramics. In water, this effect reduces the wear of coarser alumina microstructures. The wear of aluminas and of the Al2O3/TiC composite is similar; it is lower than observed in zirconia, where extended surface cracking occurs at grain sizes as small as 0.3 μm.

Grain growth suppression in alumina via doping and two-step sintering

“…Microstructure refinement in advanced ceramic materials is frequently related to improvement of mechanical properties [1][2][3][4]. Moreover, it often provides additional functionalities, such as transparency in visible and infrared wavelength range [5,6].…”

Processing of alumina-coated tetragonal zirconia materials and their response to sliding wear

“…Conversely, alumina materials offer a unique combination of high hardness (H V ffi 18-20 GPa) [2,7], corrosion resistance, thermal stability and high wear resistance [8]. The limit for the application of alumina materials is their relatively low fracture toughness (ffi3-4 MPa m 1/2 ) with associated low and variable strength [9].…”

Processing, nanoindentation and scratch testing of alumina-coated YTZP

“…Moreover, they present limitations such as environmentally assisted slow crack growth and metastable transformation of the tetragonal phase to the monoclinic phase under wet environments from room temperature up to 400 • C. Transformation results in surface roughening and microcracking, which leads to lower wear resistance [2][3][4][5]. On the other hand, alumina offers a unique combination of high hardness (H V ≈ 18-20 GPa) [2,7], corrosion resistance, thermal stability and high wear resistance [8]. However, it has relatively low fracture toughness (≈2.5-4 MPa m 1/2 ) and low and variable strength [9].…”