| Solid lubrication can solve the friction and wear problems at high temperature, ac-uum, overloading, corrosive, radioactive and other harsh environments. There are gener-ally three types of solid lubrication:1).The Polymer composite with solid lu-bricant has lower friction and wear, and lower price too, but can’t resistant to hightemperature and heavy load;2).Thin film solid lubricating material can achieve low friction, wear and controllable film thickness, but the limited film thickness shorted service life in extreme-ly harsh environment;3).The metal or inorganic base compo-sites with solid lubricant had the longer life for the whole material, lower friction and wear, high temperature and overloading capable. But it influence greatly on itsperformance that the choice of the base material and lubricant, preparation process etc. Metallurgical self-lubricating bearings had very higher requirements on materialsdue to the high temperature and heavy load, dust and other harsh working conditio-ns. Sliding bearing is commonly used with Fe, Cu, Al matrix composites, the high temperature strength was not enough. Ni, W, Ta, Co ma-trix composites can’t be pr-omoted in the civilian equipment for its high cost. In view of above situations, Nibase superalloy scrap was prepared to alloy powder by water atomi-zation. The Ni-W-Cr matrix high temperature solid self-lubricating bearing materials were prepared to meet high temperature environment.The following studies were done and get relevant results:1.The high temperature Ni-W-Cr matrix powder was made from aircraft enginesup-per alloy scrap by water atomization. The influence on the physical/chemical pr-operties, with adjusting different atomization and reduction process parameters were studied. The results showed that:More fine-grained raw powder obtained with the higher smelting temperature1200℃and higher pressure water15MPa during atomi-zation process,100mesh powder rate can reach92%; The oxygen content of powder can obviously reduce with the nitrogen atmosphere protection, decreased to52%;the Ni-W-Cr raw powders were greatly improved in bulk density and flow propertietoo. Iirregular particles were obtained easily which improved the comprehensive str-ength of composites. Appropriate reduction parameters (reduction temperature, reduc-tion time, material thickness and re-ducing gas flow) have a great influence on the pre-alloy particles together and amount of oxygen reduction.2. Based on the previous work, the high temperature Ni-W-Cr composites withdif-ferent series of lubrication were prepared by powder metallurgy. The mechanical proper-ties, the friction and wear were tested.(1) The Ni-W-Cr matrix composites were prepared with different content of gr-aphite and MoS2adding by cool press (CP) and hot pressing (HP) sintering pro-cess.The sintering process, load and environment temperature were also studied on tri-bo-logical performance. The results showed that:The composite improved its density, mechanical strength obviously by HP technology.1150～1200℃is appropriate sinter-ing temperature, otherwise,the composite appeared burnt if over1250℃. During the sinter-ing,WC hard phase appeared, and dispersed strength effect. Ni, Cu and Fe g-enerated infinite solid solution and improved the composite strength. MoS2was dec-omposited partly,and generated a low shear stress of CrxSx+1, WS2and FeS phases which improved the high temperature tribological properties.The friction coefficientsincreased slowly with the increasing temperatures. The friction coefficient decreased in300℃along with the load increasing, which showed good bearing capacity un-der high temperature. The Ni-W-Cr matrix composite added with4.5wt.%MoS2and2.5wt.%graphite had better coordinating roles. The transfer lubrication film greatly improved the composite in fric-tion properties from RT to600℃.Tt was ma-inly fatigue wear at RT. Abrasive and adhe-sive wear and oxidative wear at high te-mperature.(2) Using Ni-W-Cr alloy as substrate to prepare self-lubricating composite add-ng WS2and PbO. The composite can obtain significantly lower friction coefficient and wear rate than pure substrates. The composite generated new phases PbWO4, CrxSx+1. The composite with5wt.%WS2and4wt.%PbO reached the minimum friction coefficient and wear rate under high temperature. It had better properties at low speed and overload-ing cases, the average friction coefficient was0.16and rel-atively stable under90MPa.(3) The composites were prepared with Ni-W-Cr powder, copper, h-BN and graphite by PM with argon protection.It was found that the density and compressive strength de-creased with h-BN increasing. With the increase of temperature, the friction coefficient decreased, and had widly temperature lubrication performance, But the wear rate in-creased obviously. It was fatigue wear and adhesive wear at high temperature.3.The Ni-W-Cr matrix self-lubricating composite material was prepared and pr-ocessed to joint sliding bearing for high temperature equipment in steel rolling ent-erprise (such as mold foot roller, conveying sticks, etc.). The practical application of assessment shows that:The Ni-W-Cr matrix solid self-lubrication composites bea-ring have excellent anti-wear and low friction properties, high bearing capacity and greatly improves the service life of equipment,which greatly improves the service life of roller equipment, prolongs the maintenance cycle, reduces product cost and improves the eco-nomic benefit. |
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