Research On Tribological Properties Of Some Materials In Water Environment

Water lubrication is environmental friendly and has excellent security as well asrelatively lowcost. It has been used in fields of medicine industry and food industry.There are many water-lubricated friction pairs used in underwater operations, oceandevelopment and light-waternuclear reactor. The master’s thesis deals with tribologicalproperties of chromium plating layers on surfaces of some nuclear grade materials andPOM in water environment. Their wear mechanisms and water lubrication effects havebeen simply investigated. The main results of this thesis are as follows:(1) It is important for operational reliability of friction pairsof nuclear gradematerials which run in pure water (deionized water) environment that hard chromiumlayersthick enough are platedon friction pairs’ surfaces. Results showed that under thegiven condition of this thesis in five groups of friction pairs(group III~VII) with hardchromium layersthick enough including an friction pair constituted by a ring of304NGstainless steel with a chromium plating layer0.010~0.014mm thick against a ring of0Cr15Ni70Ti3AlNb Inconel alloy with a chromium plating layer0.010~0.014mm thickthere appeared mild abrasive wear. It is noteworthy that the average amounts of wear ofthe five groups of friction pairs were almost the same. The fact means that they had samewear characteristics which wereindependent from type of base materials of friction pairsand thickness of chromium plating layers when hard chromium layers were thickenough(>0.014mm) on friction pairs’ surfaces.(2) For0Cr17Ni12Mo2/POM friction pair running in deionizedwaterenvironment,water-pressure simulated effects markedly and regularly on the wearextent of POM and the friction coefficient of0Cr17Ni12Mo2/POM pairs. The wear ofPOM and the friction coefficient of0Cr17Ni12Mo2/POM pairs reduced withincreaseofwaterdepthsimulated within0~300m. When0Cr17Ni12Mo2/POM friction pairranin the deionized water environment of water depth simulated within0~300m, thereappearedmicro-cuttingtopography on the friction surface of POM, and its dominant wearmechanism was abrasive wear.(3) The corresponding numerical simulation results showed that when waterpressure within0~3MPa the pressed depth by the stainless steel pin into the POM discreduced with thewaterdepth (environment pressure of water). The result of numericalsimulation could partly explain the test conclusion that the wear extent of POMreduced with increase of water-pressure simulated.(4) Water absorption of POM and UHMWPE tended to decrease with the rise of environmental pressure of water within0-3MPa. Water absorption of POM is far greater than UHMWPE under all kinds of hydraulic pressure.(5) Molecular dynamics model of POM and UHMWPE which contained water has been build. It has been found that water molecule was bonded with UHMWPE molecular chain by means of Van der Waals force, and that water molecule was bonded with POM molecular chain by means of Van der Waals force and hydrogen bonds, and explained the water absorption of POM and UHMWPE.