The overall objective of this study is to introduce a wear map of ceramics which shows the regions of dominant wear modes observed in a wide range of materials and operating conditions. Furthermore, from the wear map, common necessary conditions for the application of various ceramics as wear-resistant tribo-materials in a wide range of operating conditions are discussed. For this purpose, friction and wear tests are carried out using three kinds of ceramics sliding against themselves under various contact pressures, sliding velocities and temperatures. Sliding wear phenomena of ceramics observed in all tests can be classified into two types: "mild wear" and "severe wear", based on the ratio of worn surface roughness Ry to the mean grain size Dg. The specific wear amount is always less than 10-6 mm3 (Nm)-1 when the worn surface roughness becomes relatively small (Ry/Dg < 0.2) in the mild wear region. On the other hand, the relatively rough worn surface (Ry/Dg > 0.5) in the severe wear region gives a wear rate larger than 10-6 mm3 (Nm)-1. The mild wear region is believed to be necessary for the application of ceramics as wear-resistant tribo-materials. The critical condition for mild and severe wear is analyzed with an intergranular fracture model from the view points of both mechanical and thermal aspects. A wear map of ceramics, which can define the regimes of mild and severe wear, is introduced using two dimensionless parameters, namely the mechanical severity of contact (Sc,m) and the thermal severity of contact (Sc,t), which are used as vertical and horizontal axes, respectively. The availability of the wear map constructed by this method is proven by the experimental results observed over a wide range of test materials and operating conditions.
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