| With the development of industry,the performance requirements of sliding electrical contact materials such as brush are getting higher and higher.As a new type of brush,metal fiber brush has broad application prospects under high current density and non-lubricated conditions due to its special structure.The copper fiber brush and silver fiber brush comprised of many highly oriented and uniformly distributed fibers was prepared by the knitting method with packing fraction of 20%.The effects of current on friction and wear properties and sliding electrical contact properties of Cu-C brush,copper fiber brush and silver fiber brush when sliding against GCr15 steel plate were studied.The worn surfaces of brushes and the steel discs were characterized to reveal the involved wear mechanisms.The details were shown as follows:(1)The effect of current on the friction and wear properties of Cu-C brush was studied.It was found that the friction coefficient of Cu-C brush decreased with the increase of current,and the wear rate increased gradually from 0.350×10-6 mm3/(N·m)at 0 A to 1.722×10-6 mm3/(N·m)at 8 A.The electrical wear rate was proportional to the contact resistance power.The effect of current on the sliding electrical contact performance of Cu-C brush was studied.It was found that the contact resistance and electrical noise of Cu-C brush decreased with the increase of current density,which could be attributed to the softening of Cu-C brush material caused by current thermal effect.The effect of current on the wear mechanism of Cu-C brush was studied.It was found that the main wear mechanism of Cu-C brush without current was adhesive wear.With the increase of current,the main wear mechanism gradually changed into abrasive wear,which was related to the formation of lubricating film on the friction surface and the increase of wear debris and oxidation.The effect of current on the wear mechanism of Cu-C brush was studied.It was found that the main wear mechanism of Cu-C brush without current was adhesive wear.With the increase of current,the main wear mechanism gradually changed into abrasive wear,which was related to the formation of lubricating film on the upper surface of the friction surface,the increase of wear debris and its oxidation.(2)The effect of current on the friction and wear properties of copper fiber brush was studied.It was found that with the increase of current from 0 A to 8 A,the friction coefficient of copper fiber brush increased,and the wear rate increased from 1.22×10-5 mm3/(N·m)to 5.67×10-5 mm3/(N·m),in which the electrical wear rate was proportional to the contact resistance power.The influence of current on the sliding electrical contact performance of copper fiber brush was studied.It was found that with the increase of current from 2 A to 8 A,the contact resistance decreased from 560 mΩ to 130 mΩ,and the electrical noise also showed a similar downward trend,which can be attributed to the micro welding of contact points caused by arc.The effect of current on the wear mechanism of copper fiber brush was studied.It was found that under the condition of no current,the main wear mechanism of copper fiber brush was slight adhesive wear,and under the condition of low current,the main wear mechanism was moderate adhesive wear.Under high current,the electrical wear caused by arc erosion became the main wear mechanism of copper fiber brush,and serious oxidation occurred.(3)The effect of current on the friction and wear properties of silver fiber brush was studied.It was found that the friction coefficient of silver fiber brush increased with the increase of current,and the wear rate increased gradually from 0.67×10-5 mm3/(N·m)at 0 A to 2.85×10-5 mm3/(N·m)at 8 A,which was increased by about 4 times.The electrical wear rate was proportional to the contact resistance power.The effect of electric current on the sliding electrical contact performance of silver fiber brush was studied.It is found that the silver fiber brush can reach a stable contact resistance after initial running-in.The contact resistance decreases from 34.3 mΩ at 2 A to 19.4 mΩ at 8 A,and the electrical noise also shows a similar downward trend,which can be attributed to the micro-welding of contact points and the plastic deformation of fiber tip caused by arc.The effect of current on the wear mechanism of silver fiber brush was studied.It was found that the main wear form of silver fiber brush was adhesive wear under the condition of no current or low current.At high current,the wear mechanism of silver fiber brush was serious adhesive wear and electric wear caused by arc erosion.At this time,the electric wear was more serious than mechanical wear,but no serious oxidation occurred. |
