Friction and Wear Behaviors of Nanocrystalline Surface Layer Prepared on Deposited Layer

A nanocrystalline surface layer was fabricated on a deposited layer by using pre-forceing rolling technology. The microstructural features of the treated surface layer were characterized using scanning electron microscopy and transmission electron microscopy observations. The tribological behavior of the nanocrystalline surface layer was investigated under dry conditions by using CETR-3 tribo-meter. The grain size of the nanocrystalline surface layer of about 10 μm thickness was about 10nm in the top surface layer. Nanoindentation tests indicate the hardness of the top nanocrystalline layer was about 3 times of that of the matrix. Experimental results show that the friction coefficients and wear volume of the surface nanocrystallized samples were lower than those of the untreated samples. The friction coefficient and wear volume were reduced approximately by 10%, 28%. After surface nanocrystallization, the dominant wear mechanism was abrasive wear rather than abrasive wear and adhesive wear. The advantages in the friction and wear properties of the treated sample may be attributed to the enhancement of both the hardness and the surface activity by the grain refinement, which, in turn, result in the improvements in producing oxide layer and resistance to plastic removal.