Wear and friction behaviour of Si3N4 ceramics under diesel and biodiesel lubrication

The wear and friction behaviour of self-mated silicon nitride pairs in lubricated ball-on-flat reciprocating sliding conditions is the subject of the present work, using diesel fuel and soybean biodiesels as lubricants. The results show that the friction coefficient is considerably higher for the diesel fuel than for biodiesels in the stationary regime (about 0.14 and 0.06, respectively). The wear coefficient values are in the range 10−8–10−9 mm3/N·m, denoting a mild wear regime, in agreement with the high lubricity of these fuels assessed by the ASTM D 6079 standard. The observed wear mechanisms were mainly mechanically dominated, consisting of transgranular and intergranular fractures, and the formation of a tribolayer by plastic deformation of the wear debris.