Abstract: In order to explore the coverage value and its influence after shot peening on the surface of carburized steel samples, this paper analyzes the contact size of single particles from the theoretical calculation of coverage, and verifies the theoretical results through experiments. In order to obtain the effect of surface coverage on residual stress, morphology and roughness, 18CrNiMo7-6 carburized steel samples are shot peened with different coverage on a special pre-mixed jet equipment platform. The results show that when the coverage rate increases from 2 500 % to 25 000 %, the surface roughness fluctuates slightly, but generally shows an upward trend, and the maximum residual stress value of the surface layer gradually increases. The increase of coverage has no obvious effect on the depth of residual stress layer, which only increases slightly under higher energy impact, with a change of 30 μm, but too high coverage will reduce the residual compressive stress on the surface of the sample. Therefore, considering the two factors of surface roughness and residual stress, the surface strengthening of this carburized steel should keep its coverage in the range of 2 500 %-10 000 %.

Key words: pre-mixed jet, carburized steel, coverage, residual stress, roughness