Effects of normal nitriding process with 280 Pa at 560 ℃ for 12 h and cycling plasma nil rich: g process with 170 Pa at 560 °C for 3 h then quick cooling to ambient temperature on structure

hardness

gradient of hardness

and wear resistance of nitride layer of steel 38CrMoAl ( % ： 0. 35 - 0. 42C

1. 35 ~ 1.65 Cr

0. 15 - 0. 25 Mo

0. 70 - 1. 10 Al) have been tested. Results show that the cycling plasma nitriding process is available to decompose ε phase at surface layer

led to favorable nitriding of γ′ phase in steel: in the condition of getting same surface hardness of nitrided layer and gradient of hardness

the nitriding rate by cycle plasma nitriding process is obvious high than that by normal nitriding process

and the wear resistance of nitrided steel is improved.