Friction and wear behaviors of nanocrystalline surface layer of chrome–silicon alloy steel

A nanocrystalline surface layer of about 25 μm thickness was fabricated on a quenched and tempered chrome–silicon alloy steel using Supersonic Fine Particles Bombardment (SFPB). The microstructural features in the treated surface layer were characterized using scanning electron microscopy and transmission electron microscopy observations. The grain size is about 16 nm in the top surface layer. Nanoindentation tests indicate the hardness of the top nanocrystalline layer is about 2 times of that of the matrix. The tribological behavior of the nanocrystalline surface layer was investigated under dry conditions. Experimental results show that the friction coefficients and wear volume loss of the surface nanocrystallized samples are lower than those of the untreated samples, and the wear resistance is remarkably improved. After surface nanocrystallization, there occurs a transition of dominant wear mechanics from the combined action of abrasive wear and adhesive wear to the abrasive wear. The advantages realized in the friction and wear properties of the SFPB treated sample may be attributed to the duo enhancement of the hardness and the surface activity caused by the grain refinement, which, in turn, result in the improvements in forming oxide layer and resistance to plastic removal.