Research On Tribological Behavior Of TiN Coating On Bearing Steel Against Electroplating Silver Layer

M50NiL steel is a bearing steel with excellent toughness and anti-fatigue property. But it is easy to produce the abnormal wear phenomenon of “soft grinding hard” when contact with the cage of low hardness during high-speed, overloading, vibration environment, due to the small carbide particles in M50 NiL do not appear to reduce the cutting action of abrasive particles. As the representative of hard coating, the hardness of TiN coating is more higher than the M50 NiL after carburizing, so it will protect the bearing guide surface effectively. This paper studied the deposition parameters of TiN coating by multi-arc ion plating under low temperature in order to get the parameters after optimizated, then the protective capability of TiN coating is analysied by the wear test that carried out in the contact mode of impact sliding and ball on disc.The deposition temperature of traditional TiN is about 500℃, but it will cause the changes of micro-structure and grain of the steel. So it is necessary to make sure the temperature below 300℃. At the end come to conclusions that arc flow had the gteatest influence on the coating hardness; high pressure helps to reduce the number of particles on the surface, although results of low hardness and strength; bias will increase the hardness of the coating duing to improve the energy of ion bombardment within a certain scope, but it does not play an important role in improving the number and size of particles. Fine particles size, high hardness and good adhesion TiN coating was successfully deposited after optimized finally.The wear resistance of TiN coating is discussed with M50 ball, the results showed that TiN coating had excellent abrasion resistance, but it will failure in the form of layered peeling under high load. the wear mechanisms are mainly adhesion wear, abrasive wear, oxidation wear possibly during the process of test.The friction behavior of TiN-Ag was studied under the contact of ball on disc. Along with the load and speed increaing, the friction coefficient increases when no lurication, because the contact area growing dynamically and also may not found the transfer film between the friction pair, but the friction coefficient is lower with low load and speed. However, the TiN coating does not have obvious wear phenomenon compare with M50. When some oil was injected, the minimum friction coefficient reach to 0.1, the TiN coating reflect well abality to reduce friction and wear.Tribological behavior of M50 NiL、M50、TiN-Ag was analyzed under the contact of impact sliding. The abrasion of M50 NiL is more larger than M50 duing to the distribution and size of carbides in the micro-structure. However, the TiN coating provided excellent protection for the steel without obvious wear. When the contact stress reach 43.5MPa, fall off of TiN coating was found in some area on the coating caused by the high temperature and the effect of thermal fatigue during the impact repeatedly.