The artificial joint acetabular material ultrahigh molecular weight polyethylene (UHMWPE) was reinforced with carbon fibers (CF) indifferent contents. The effects of CF content on hardness and tribological properties of the materials were studied. The morphologies of wearsurfaces were examined with a Scanning Electron Microscope (SEM). The results show that the hardness and wear resistance of CFreinforcedUHMWPE composites increased with CF content; the friction coefficients under distilled water lubrication were decreased greatlyby the addition of CF; that adherence, plowing, plastic deformation and fatigue wear are dominant for the UHMWPE under dry sliding, andthat abrasive wear and drawing out of CF from the wear surface of the composites are dominant for the CF-UHMWPE composites under bothdry and distilled water lubrication conditions.

The MoS2 powders were coated with Al2O3 (5 wt.%) through controlling hydrolysis of Al (NO3)3•9H2O. MoS2 powder coated with Al2O3 waswritten as MoS2/Al2O3 hereinafter. MoS2/Al2O3 powders were put into Ni plating electrolyte bath. Cetyltrimethylammonium bromide (CTAB)—the surfactant was also put into the bath. The experiment proves that MoS2/Al2O3 particles were absorbed onto the Ni plate. The amount of MoS2/Al2O3 deposited on Ni plate rises with the increasing concentration of MoS2/Al2O3 in the bath. The microhardness, micro-surface, phase and thetribological property of the MoS2/Al2O3 multi-plating coating were measured and analyzed. The performances of microhardness and wearresistance of the Ni-MoS2/Al2O3 composite are better than those of Ni-MoS2 composite.

In this study, a new two-step plasma immersion ion implantation technique was developed and applied for the modification of Ti6Al4V alloy; firstly ion implanting with nitrogen at high temperature and followed with oxygen in high dose. A graded titanium oxide-titanium nitride film wasobtained on the surface of the Ti6Al4V alloy. The contact angle and the microhardness of the modified alloys were measured. The friction andwear properties of UHMWPE rubbing against the modified alloys under lubrication of distilled water were investigated using a pin-on-disctribometer. The wettability and the microhardness of the alloy surfaces were found to be increased significantly after ion implantation. The frictioncoefficient decreased by nearly 5 times and the wear resistance of UHMWPE increased by about 40 times against the ion implanted Ti6Al4V alloy.Many deep furrows were found on the surface of the un-implanted alloy and were absent in the ion implanted surfaces of the alloy.

Many biomaterials are being developed to repair or replace articular cartilage. One of these materials, poly(vinyl alcohol) (PVA) hydrogelprepared from aqueous solution of the polymer by freezing and thawing method may exhibit the mechanical properties required to withstand theharsh environment of diarthrodial joints. To better understand how PVA hydrogel friction is affected by different variable factors, a three-factor,three-level designed orthogonal experimentwas developed. Factors include lubricant, sliding speed, and normal load. Friction coefficient of the PVAhydrogel was found to depend significantly on load and sliding speed. Lubricant had little effects on the friction coefficient. Friction coefficient ofthe PVA hydrogel decreased with the increase of sliding speed and the friction coefficient approximately increased linearly with the increasing load.Average friction coefficient decreased from 0.0447 to 0.0379 while the sliding speed increased from 0.06 to 0.22m/s. Average friction coefficientincreased from 0.0276 to 0.0546, almost increasing one time, while the load increased from 5 to 15 N.

Laser surface texturing technology has some advantages in reducing friction and wear ofmechanical parts in industry. In this paper, a Nd:YAG laser was used to generate microporeson T8 steel surface and the structure and morphology features of surface micropores wereobserved. Tribological experimentswere conducted with a ring-on-disc tester under variousloads and speeds. It is shown that the maximum PV value of face seal can be increased byhydrodynamic effect of micropores.

Friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against Al2O3 ceramic under dry sliding,and lubrication of fresh plasma, distilled water and physiological saline were investigated with a self-made pin-on-disk apparatus at37±1℃. The worn surfaces were examined with a scanning electron microscope (SEM). The results show that the friction behavior ofUHMWPE is very sensitive to its water absorption state. The wear rate of UHMWPE under dry sliding is the highest and under plasmalubrication is the lowest. The wear mechanisms are different under dry friction and various lubricating conditions.

Nanohydroxyapatite reinforced poly(vinylalcohol) gel (nano-HA/PVA gel) composites has beenproposed as an articular cartilage repair biomaterial. In thispaper, nano-HA/PVA gel composites were prepared byin situ synthesis nano-HA particles in PVA solution andaccompanied with freeze/thaw method. The influence ofnano-HA content, PVA concentration, test frequency andfreeze/thaw cycle times on the viscoelastic behavior ofnano-HA/PVA gel composites were evaluated usingdynamic mechanical thermal analysis (DMTA). The resultsshowed that both storage modulus and loss modulus firstlyincreased and then presented decreasing trend with the riseof nano-HA content. Their maximum values were obtainedwhile nano-HA content was 6%. Furthermore, the G0 andG@ of the composites improve with the increase of PVAconcentrations and freeze/thaw cycle times. This effect wasmore distinct at low freeze/thaw cycles. The phase angle(tan d) of the pure PVA gel is larger than that of the nano-HA/PVA composites at the test frequency spectra, but allthe phase angle values of the tested composites were closeto that of nature bone.

Wear is the primary cause of failure of joint replacement prostheses. In this paper, the ultrahigh molecular weight polyethylene(UHMWPE) was implanted with Oq and Cq ions at different energies and doses. Its friction and wear behaviors were studiedunder dry friction, lubrication of distilled water and blood plasma using a pin-on-disk tribometer with a Si3N4 ceramic ball as thecounterface. Scanning electron microscopy was used to examine the surfaces of un-implanted and implanted UHMWPE beforeand after wear. The experimental results show that the wear resistance of the implanted UHMWPE is higher than that of the unimplantedUHMWPE under dry friction, lubrication of distilled water and blood plasma. The wear resistance of the Oq-implantedUHMWPE is better than that of the Cq-implanted, especially for 450 keV energy and 5=1015ycm2 dose Oq-implanted sample,of which the wear rate is the lowest. The wear rates of the implanted and un-implanted UHMWPE are higher under dry frictionthan under the blood plasma lubrication. The adhesion, ploughing and plastic deformation are the wearing mechanisms for theun-implanted UHMWPE, while the fatigue and abrasive wear for the implanted UHMWPE.

Ni-Cr-based alloys with excellent self-lubricating property in a wide temperature range were prepared by powder metallurgical hotpressing of alloyed Ni-Cr powder, Mo, Al, Ti, B and various proportions of MoS2 powder. The effects of MoS2 on some mechanical andtribological properties of the alloys when rubbing with W18Cr4V high-speed steel were investigated in the temperature range of 20-600℃. The results showthat the anti-bending strength of the alloy decreases with addition of MoS2, and the tribological properties of the alloy wereimproved by adding MoS2. The best comprehensive properties of mechanics and tribology were obtained when the amount of MoS2 in thealloy is up to 10 wt.%. XRDanalysis shows that the alloywas mainly composed of Ni-based solid solution, Ni3Al, CrxSy,MoS2 and Mo2S3. The selective transfer of oxides between rubbing pairs occurs in the friction process at 600℃. The glaze layer is formed on the oxide film atworn surface of the alloy during high temperature friction process. The hardness of the glaze and oxide film is higher than that of the matrixalloy, which accounts for the wear resistance of the alloy at high temperature. The synergistic action of oxides and residual sulfides in thewear surface and wear debris at high temperature is responsible for reduction of friction.

Solid lubricating materials are necessary for development of new generation gas turbine engines. Nickel-based self-lubricating compositeswith graphite and molybdenum disulfide as lubricant were prepared by powder metallurgy (P/M) method. Their tribological properties weretested by a MG-2000 high-temperature tribometer from room temperature to 600 ◦C. The structure of the composite was analyzed by XRD andworn surface morphologies were observed by optical microscope. The effects of counterface materials on tribological behavior of compositeswere investigated. It was found that chromium sulfide and tungsten carbide were formed in the composite by adding molybdenum disulfide andgraphite, which were responsible for low-friction and high wear-resistance at elevated temperatures, respectively. The average friction coefficients(0.14-0.27) and wear rates (1.0-3.5×10−6mm3/(N m)) were obtained for Ni-Cr-W-Fe-C-MoS2 composite when rubbed against silicon nitridefrom room temperature to 600℃ due to a synergetic lubricating action of graphite and molybdenum disulfide. The optimum combination ofNi-Cr-W-Fe-C-MoS2/Ni-Cr-W-Al-Ti-C showed lower friction than other counter pairs. The graphite played the main role of lubrication atroom temperature, while sulfides were responsible for low friction at high temperature.