Research Of The Friction And Wear Behaviors Of MoSi₂ And MoSi₂-based Composites At Elevated Temperature

Because of the oxidation resistance and high melting point,MoSi₂ will be expected to use as a new type of wear resistant material under high temperature circumstance,as its higher hardness and elastic modulus.In this paper,MoSi₂ and MoSi₂-based Rare Earth(0.8wt%) composites were prepared by SHS,and vacuum sintered at high temperature.Silicon carbide and silicon nitride were used as friction disc,while MoSi₂ and MoSi₂-based composites as pin.The effects of different temperatures(700～1100℃),loads(10N～50N),sliding velocity(0.084m/s～0.252m/s) and different sliding couples on its high temperature frictional and wear properties were investigated by using XP-5 type High Temperature Friction and Wear Tester. Microphotograph and phase status of worn surface of sliding couples were observed by SEM and X-ray.Then,the wear mechanism was studied.Studies provide reference to its application as high temperature and wear resistant materials The results are shown as follows:1.Results show,the main wear mechanism of MoSi₂/SiC sliding couple is adhesion and abrasion at the range of 700℃～900℃under 30N at 0.126m/s.It has better wear resistance at the range of 1000℃～1100℃.When the loads are between 10N～50N,The wear mechanism of MoSi₂ change from adhesion and abrasion to fatigue fracture and oxidation wear.The friction coefficient and wear rate do not change acute under above 30N.The friction coefficient and wear rate reduce with the increase of the sliding velocity changed from 0.084m/s to 0.252m/s under 30N at 1000℃.Main wear mechanism of MoSi₂ change from abrade,abrasion to fatigue pitting corrosion and oxidation wear.2.The friction coefficient and wear rate of MoSi₂ against Si₃N₄ are inferior to MoSi₂ against SiC under the equal conditions.Wear mechanism of MoSi₂ change from abrasion to oxidation when the temperature are between 700℃～1100℃under 30N at 0.126m/s.The sliding couple has better wear resistance above 1000℃.The friction coefficient of MoSi₂ against Si₃N₄ reduces with load increase which change from 10N to 50N,but the wear rate increases.The main wear mechanism is sequentially adhesion and abrasion.When the sliding velocities are between 0.084m/s～0.252m/s,wear mechanisms of MoSi₂ are abrasion and oxidation wear. 3.After adding rare earth phase(0.8wt%) to MoSi₂,its friction coefficient and wear rate decrease under the same conditions.The wear weight loss of rare earth-MoSi₂ is much smaller compared with pure MoSi₂,as temperature and sliding velocity increase.However,loads have lower impact on its wear resistance.The main wear mechanism is adhesion,and it has abrasion with temperature increase.The main reason of its friction coefficient and wear rate rising is oxidation and adhesion aggravate.