Evaluation of scuffing behavior of single-crystal zirconia ceramic materials

Scuffing, described as sudden catastrophic failure of lubricated sliding surfaces, is usually characterized by a sudden rapid increase in friction, temperature, and noise, and is an important failure mode on sliding surfaces. In metallic materials, scuffing results in severe plastic deformation of surfaces in contact. This study evaluated the scuffing behavior of two variants of zirconia (ZrO2) ceramic. Using a block-on-ring contact configuration and unformulated polyalphaolefin (PAO) lubricant, step-load-increase scuffing tests were conducted with single crystals of cubic ZrO2–9.5% Y2O3 and tetragonal ZrO2–3% Y2O3. Phenomenological “scuffing”, characterized by a sudden rise in friction coefficient and noise, was observed in the cubic material. For this material, “scuffing” occurred by sudden fracture at the end of test. The tetragonal material underwent no sudden failure (scuffing). This lack of scuffing is attributed to the sequential operation of three plastic deformation mechanisms: ferroelastic domain switching, tetragonal-to-monoclinic phase transformation, and dislocation slip as the frictional stress and energy dissipation pathway.