Wear of advanced ceramics

The modes of wear of ceramics can be briefly described as mild wear and severe wear. For mild wear, tribochemical reaction forms a relatively soft and thin surface layer which is detached from the surface as thin flakes or dissolves in water. In addition to tribochemical wear, mild wear takes place by mechanically forming fine wear debris. They are smaller than the grain size by one-tenth or less and have the original chemical composition. Wear rate remains below 10^-6 mm³/(Nm) and the maximum surface roughness is in the order of one-tenth of the grain size. For severe wear, wear debris is formed by mechanical cracking of grains or delamination of tribo-films on the scale of the grain size. Wear rate is higher than 10^-6 mm³/(N m) and the maximum surface roughness is in the order of the grain size. The mild and severe wear modes can be distinguished by the ceramic wear map in terms of the mechanical severity of contact Sc.m and the thermal severity of contact S_c.t.