Study On Wear Behavior And Mechanism Of Three Typical Bulk Metallic Glasses And Brass

Traditional sliding bearing systems are made of steel-brass friction pairs.With the development of technology,devices will become more miniaturized and more precise in the future.It is difficult for the traditional steel shaft to meet the mechanical requirements such as strength while ensuring the dimensional accuracy.The development of new materials is undoubtedly the key to solve this bottleneck.As a new type of metallic material,Bulk Metallic Glass(BMG)has many property merits,such as high strength,high hardness,small specific gravity,corrosion resistance and good wear resistance.As a result,BMG bearings will become smaller,lighter,and stronger and will be the most competitive candidate for bearing materials in the future.This thesis studied the sliding friction and wear properties of NiB,ZrB,CuB with brass under different lubrication conditions,GCr15 steel is used as the reference material.Research foundings are as follows.Under the dry friction: Similar to the GCr15 steel,the wear mechanism of NiB,ZrB,CuB is mainly abrasive wear,supplemented by adhesive wear.All BMGs exhibit better friction properties under dry friction.And the wear rate of high-strength brass against BMG is only 80-90% of against GCr15 steel.Meanwhile,the friction coefficient of BMG is almost the same as GCr15 steel’s,and it decreases as load or speed increases.Under the grease condition: Similar to GCr15 steel,the wear mechanism of BMG is mainly abrasive wear,supplemented by adhesive wear.The high-strength brass against BMGs has a considerable wear rate with that against GCr15 steel.At low speed,the wear rate of highstrength brass against ZrB and CuB is 4.1%-9.6% lower than that against GCr15 steel.Like GCr15 steel,the friction coefficient of BMG and GCr15 steel increases with speed.Under the same conditions,the wear of H59 brass against BMG is 69.1% higher than that of high-strength brass,and the average coefficient of friction of H59 brass is 0.08 higher than that of highstrength brass.The compatibility of high-strength brass and BMG is better than H59 brass.Compared with the condition of dry friction,the wear of high-strength brass against BMG is 29.5% lower than that under the grease condition.Under oil condition: Compared with GCr15,the main wear mechanism of BMGs is abrasive wear.And BMGs exhibit better friction and wear properties at low and high speeds.At the speed of 1 mm/s and 10 mm/s,the average wear of high-strength brass against BMGs is only 65% and 56.1% of that against GCr15 steel,respectively.The tendency of the friction coefficient of GCr15 steel and BMGs decreases with increasing of load or speed.Comparing to other BMGs,the brass against NiB has the least wear loss,which indicates that NiB is more suitable to work at the oil condition.Compared with dry friction and grease conditions,the wear rate of brass against BMGs is 3% less than that under lubricating oil.The average coefficient of friction is reduced by 0.09.Under solid lubricant condition:The brass exhibits an undetectable wear loss under this circumstance.The friction coefficient of BMG decreases firstly and then increases with the load and sliding velocity.Compared with the same load and sliding velocity,the average friction coefficient of BMG is 36% lower than that under oil condition.BMGs are more suitable for operating at low load of no more than 1 kg(3.12 MPa)or below 5 mm/s.Above all,BMGs have considerable or superior wear behavior than GCr15 steel under dry and grease lubrication condition.At low loads condition,BMGs do not exhibit adhesive wear,which is different from GCr15 steel.Under oil condition,NiB has better performances than other BMGs.At 1 mm/s,the wear rate of high-strength brass against NiB is only 52% of that against GCr15 steel,respectively.Comparing with GCr15 steel,the NiB exhibits more excellent friction and wear merits.