Tribological Properties of MoS2 Films on Piston Ring Surface under Dry Friction and Lean Oil Lubrication
Diesel engines with large power,long stroke and high explosive pressure are the main power equipment for the fields of transporta-tion,construction machinery,national defense equipment and nuclear emergency generators.During cole/hot start of the key kinematic pair piston ring-cylinder liner of a diesel engine,the upper and lower dead center positions of the cylinder liner are in a dry friction or lean oil lubrication state,which is prone to local abnormal wear and loss of power performance.In order to suppress the abnormal wear of piston ring-cylinder liner kinematic pair,MoS2 thin films were prepared on the surface of the piston ring by magnetron sputtering technology.The friction and wear performance of the friction pair of the piston ring,with MoS2 thin film added on its surface,and cylinder liner was evaluated using the SRV-Ⅳ micro motion friction and wear tester to simulate frequent cold/hot start conditions of diesel engines.Moreover,scanning electron microscopy(SEM)was used to characterize the microstructure of the MoS2 film and the surface morphology of the friction pair before and after friction.Results showed that compared with the original CKS piston ring and cylinder liner,the friction coefficient of MoS2 film piston ring-cylinder liner under dry friction condition was greatly reduced from 1.07 to 0.11,and the wear rate of cylinder liner was reduced from 8.61 × 10-6 mm3/(N·m)to 3.71 × 10-8mm3/(N·m).Under normal temperature and lean oil condition,the friction coefficient decreased from 0.18 to 0.11,and the wear rate decreased from 1.43×10-7 mm3/(N·m)to 3.22×10-8 mm3/(N·m).Under high temperature and lean oil condition,the friction coefficient declined from 0.12 to 0.08,and the wear rate was reduced from 7.08x10-8 mm3/(N·m)to 1.12×10-8 mm3/(N·m).Besides,the transfer of MoS2 films on the surface of the piston ring during the friction process was the main reason for the improvement of the tribological performance of the friction pair.
piston ring and cylinder linerMoS2 filmsmagnetron sputteringtribological properties
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