| Aero-engine gear pump gear shaft with sliding bearing material as a kind of tin bronze,has good casting and machining properties.As a typical bearing material,Cu-15Ni-8Sn alloy is widely used in the field of bearing materials because of its excellent wear resistance and mechanical properties.In this paper,Cu-15Ni-8Sn/graphite self-lubricating composites with different graphite contents were prepared using Cu-15Ni-8Sn as the matrix material and graphite as the solid lubricating phase by using Spark plasma sintering technology and free sintering technology,respectively,and selecting commercial copper powder,nickel powder,tin powder and graphite.The effects of two different preparation methods on the mechanical and tribological properties of the materials were investigated to derive the optimal composition formulation,and also to investigate whether the tribological wear properties of the copper alloy-based self-lubricating composites prepared by different methods under oil lubrication conditions meet the standards of tin bronze.The following conclusions were drawn:(1)When the composites were prepared by Spark plasma sintering technology,the mechanical properties such as densities,hardness and strength were significantly improved compared with those prepared by free sintering technology;the hardness of Cu-15Ni-8Sn/graphite self-lubricating composites prepared by Spark plasma sintering technology showed a first increase and then decrease,and the hardness of the composites was maximum when the graphite was added at 3%;the compressive strength of the composites gradually decreased with the increase of graphite content.(2)Under dry-friction conditions,the frictional wear properties of the composites prepared by the spark plasma sintering technique under dry friction conditions compared with those of the composites prepared by the free sintering technique,and the wear rate of the composites prepared by the spark plasma sintering technique was lower compared with those of the composites prepared by the free sintering technique.Different graphite contents have a small effect on the wear rate of the composites,and when the graphite content is too large(5%),the wear rate of the composites increases significantly.At different loads,the composite with 3% graphite has the best friction performance,and when the load is 3N,the composite wear mechanism is mainly minor abrasive wear,and when the load is 5N and 10 N,the composite wear mechanism is mainly peeling wear of the graphite-rich lubricated layer.In the composites prepared by free sintering technology,the friction performance of composites containing 1% graphite is the best under different loads.When the load is 3N,the wear mechanism of composites is mainly peeling wear;when the load is 5N,the wear mechanism of composites is mainly abrasive wear with plastic deformation;when the load is 10 N,the wear mechanism of composites is mainly slight peeling and fatigue fracture,peeling wear.With the increase of graphite content,the wear rate of composite materials gradually increases.(3)Under dry-friction conditions,the friction coefficient and wear rate of the composites are reduced because the formation of graphitic-rich lubrication layer makes the composites maintain good lubrication performance during the friction process.However,with the increase of graphite content,the lubrication film on the surface of the composites tend to break down.(4)As the whole,the composite materials prepared by SPS meet the performance criteria of tin-bronze solid lubricant material more than those prepared by free sintering technique under aviation lubricant medium,only the composites with graphite content of 1% meet the performance criteria of tin-bronze solid lubricant material. |
