This work investigated the tribological properties of M50 steel and TiN coated M50 steel against silver coatings

based on the abnormal wear existing in aerospace engine bearing. The effect of relative sliding speed

contact stress as well as the interaction between the two parameters on friction coefficient with time were analyz. SEM and EDS were used to observe the surface morphology and the compositions of the worn traces. The results show that

friction coefficient increases with sliding time

and exists an abrupt change time. With lower sliding speed and lower contact stress

the friction coefficient keeps on 0.15-0.25. However

with higher sliding speed and higher contract stress

the friction coefficient rises quickly and reaches about 0.5. Within the range of parameters in this test

the change time has an approximate linear relationship with PV value

which is the product of contact stress P and sliding speed V . Sliding with high speed and high contact stress

the scratch will occur on the surface of M50 steel by the large hard particles. TiN coating can obviously postpone the time of the high friction coefficient

and has the advantage to prevent the worn of M50 steel due to impeding the peel off of the large carbides