MoS2 and WC/C coatings were utilized to treat bolts made of 45 steel,the self-loosening behaviour of the two coated bolts were studied by lateral vibration test,and were compared with the Zinc coated bolts.The anti-loosening performance of three kind of coated bolts were discussed.The damage of the threads after tests was analyzed using scanning electron microscope (SEM) and energy dispersive X-ray (EDS),and the wear mechanisms between contact threads were revealed.It is found from test results that the main wear mechanisms of the contact surfaces between threads are delamination,abrasive wear and oxidation wear for the bolted joints coated with MoS2 coatings,and those are delamination and abrasive wear for the WC/C and Zinc coated bolts.Under the same preload or equivalent stress at the thread root,the anti-loosening performance for the MoS2 coated bolts is the worst due to the low friction coefficient,and that for the WC/C coated bolts is the best because of the excellent wear resistance.Under the same tightening torque,the anti-loosening performance for the MoS2 coated bolts is the best due to the largest preload,the next is the WC/C coated bolts,and the last is the Zinc coated bolts.