Interaction Between Nanocrystallized/N~+-implanted 316L Stainless Steel And ZDDP Lubricant Additives

316L austenitic stainless steel is widely used in mechanical field because of its excellent corrosion resistance,plasticity and toughness.However,the disadvantages such as low hardness and poor wear resistance are the limitation for its wider range of application.To solve this problem,the surface nanocrystallization and nitrogen ion implantation are adopted to improve the mechanical performance of 316 L stainless steel,and the antifriction mechanism under ZDDP lubrication is studied.After the surface nanocrystallization by ultrasonic cold forging technology(UCFT),the austenitic stainless steels were implanted by different doses of N~+.The friction and wear behaviors of the samples lubricated by PAO and PAO~+ZDDP were tested on a TRN ball-on-disk friction and wear tester.The results show that:(1)N~+ implantation can form a modified layer about 100 nm thick on the surface of 316 L stainless steel and improve its mechanical properties.The best mechanical properties are obtained at the dose of 4×1017 N~+/cm2.While surface nanocrystallization has little effect on the surface mechanical properties of stainless steel.(2)Under PAO lubrication,to all the samples,the surface improving the mechanical properties,the abrasive wear and adhesive wear were relieved,the wear rate decreaseswith the increasing dose of N~+.The UCFT treatment gives the samples higher activity,which is beneficial to the adsorption of oil film.Furthermore,the micro pits on the UCFT surface are beneficial to the storage of lubrication,and thus play a significant role in grinding.Thus,the UCFT surfaces have a better abrasion resistance.(3)The addition of ZDDP leads obvious improvement of the surfacefriction and wear properties due to the formation of the anti-wear films.While the excessive ZDDP concentration will lead to the incomplete decomposition,which will lead to theintensification of abrasive.When the ZDDP concentration is 1wt.%,the sample has the best friction and wear properties.(4)Under PAO+1%ZDDP lubrication,the UCFT surface with high activity is conducive to the adsorption and decomposition of ZDDP,as well as the depolymerization of long chain phosphate,which enhanced the anti-wear effect of ZDDP.With the increasing of the implanted dose,the surfaceactivity is improved,which promoted the adsorption of ZDDP and the depolymerization of long chain phosphates.The formation of the nitride accelerates the decomposition rate ofZDDP,which lead to the double layer structure of the phosphate film.The samples treated by UCFT and 8 × 1017 N~+/cm2 implanted has the best friction and wear properties.