Effect of surface nanocrystallization on friction and wear properties in low carbon steel

A nanocrystalline (nc) surface layer of about 10 μm thick was fabricated on a low carbon steel plate by means of surface mechanical attrition treatment. The grain size is about 15 nm in the top surface layer, and it increases with an increase of depth from the treated surface. Nanoindentation measurements indicated that hardness is enhanced in the nc surface layer relative to the matrix. Experiments show that the friction coefficient decreases and the wear resistance increases with the nc surface layer. The improvement in friction and wear properties may be attributed to the harder nc surface layer which reduces the degree of plowing and micro-cutting under the lower load and the degree of plastic removal and surface fatigue fracture under the higher load, respectively.