抽油泵柱塞等离子体浸没离子注入工艺研究

采用不同的等离子体浸没离子注入（PIII）工艺对45钢油井抽油泵柱塞进行了氮离子注入,研究结果发现,不同条件下的氮离子注入均能提高抽油泵柱塞表面的显微硬度的耐磨性,尤其采用射频等离子体浸没离子注入技术对抽油泵柱塞进行注入处理,柱塞表面显微硬度得到了显著提高,同时耐腐蚀性也明显改善。     

Sliding wear behaviour of ion implanted ultra high molecular weight polyethylene against a surface modified titanium alloy Ti-6Al-4V

A study has been made of the sliding wear behaviour of untreated and ion implanted ultra high molecular weight polyethylene (UHMWPE) against a surface modified titanium alloy (Ti-6Al-4V) using a pin on disc apparatus. It was found that the presence of water lubrication and a very smooth counterface was necessary to maintain low wear rates of the UHMWPE. A ‘zero wear’ effect was observed when nitrogen implanted UHMWPE was tested against very smooth counterfaces (R_a ≈ 0.03 μm) of either surface oxidized or nitrogen implanted Ti-6Al-4V under water lubrication. The enhanced mechanical and physical properties of the surface treated materials are believed to be responsible for the improved wear performance.     

Study on long life of artificial joints by investigating optimal sliding surface geometry for improvement in wear resistance

The effective life of artificial joints is approximately 15 years. A smooth metal sliding surface is presumably the most suitable when manufacturing artificial joints; however, the relationship between the characteristics of metal sliding surface and ultra high molecular polyethylene (UHMWPE) wear has not been confirmed. Further, there is no apparent proof that a smooth surface is the optimal option for the improvement in the wear resistance of artificial joints. In this study, we investigated the mechanism of UHMWPE wear and proved that scratch marks caused by a sliding motion against the metal surface are the prime cause of UHMWPE wear. Furthermore, we used a micro-dimpled surface as an effective sliding surface to reduce the UHMWPE wear. A 2-axes pin-on-plate sliding test proved that the life of artificial joints can be extended to approximately 35 years by using a micro-dimpled surface with 1-μm deep dimples.     

Tribological Behavior of UHMWPE Reinforced with Graphene Oxide Nanosheets

In this article, a series of graphene oxide (GO)/ultrahigh molecular weight polyethylene (UHMWPE) composites are successfully fabricated through an optimized toluene-assisted mixing followed by hot-pressing. The mechanical and tribological properties of pure UHMWPE and the GO/UHMWPE composites are investigated using a micro-hardness tester and a high speed reciprocating friction testing machine. Also, the wear surfaces of GO/UHMWPE composites are observed by a scanning electron microscope (SEM), to analyze the tribological behavior of the GO/UHMWPE composites. The results show that, when the content of GO nanosheets is up to 1.0 wt%, both the hardness and wear resistance of the composites are improved significantly, while the friction coefficient increases lightly. After adding GO, the tribological behavior of the GO/UHMWPE composites transforms from fatigue wear to abrasive wear associated with the generation of a transfer layer on the contact surface, which efficiently reduced the wear rate of the GO/UHMWPE composites.     

Torsional fretting wear of a biomedical Ti6Al7Nb alloy for nitrogen ion implantation in bovine serum

Ti6Al7Nb is a high-strength titanium alloy used in replacement hip joints that possesses the excellent biocompatibility necessary for surgical implants. Ti6Al7Nb treated with nitrogen gas (N₂) plasma immersion ion implantation–deposition (PIII–D) was investigated. Torsional fretting wear tests of untreated and nitrogen-ion-implanted Ti6Al7Nb alloys against a Zr₂O ball (diameter 25.2 mm) were carried out under simulated physiological conditions (serum solution) in a torsional fretting wear test rig. Based on the analyses of the frictional kinetics behavior, the observation of 3D profiles, SEM morphologies and surface composition analyses, the damage characteristics of the surface modification layer and its substrate are discussed in detail. The influence of nitrogen ion density on the implantation and torsional angular displacement amplitudes were investigated. The results indicated that ion implantation layering can improve resistance to torsional fretting wear and thus has wide potential application for the prevention of torsional fretting damage in artificial implants. The damage mechanism prevented by the ion implantation layer on the Ti6Al7Nb alloy is a combination of oxidative wear, delamination and abrasive wear. An increase in ion implantation concentration inhibited detachment by delamination.     

Wear properties of UHMWPE/aromatic thermosetting copolyester blends in unlubricated sliding

To improve the wear resistance of ultrahigh molecular weight polyethylene (UHMWPE), blends of UHMWPE, and an aromatic thermosetting copolyester (ATSP) (50/50, v/v) were developed, taking advantage of the crosslinked structure and good wear resistance of ATSP. As a compatibilizer, poly(ethylene-co-acrylic acid) (PEA) was added into the blends with its contents changing from 0 to 20% (w/w). Dynamometer wear tests (sliding against stainless steel surface with contact pressure ranging from 600 to 2500 kPa) showed that the UHMWPE/ATSP blend with 10% PEA had lower wear rate than the UHMWPE sample. The improved wear resistance resulted from the change of the wear mechanism. Scanning electron microscopy (SEM) images of the worn surfaces revealed that the presence of ATSP and PEA would prevent the lamellar alignment in the UHMWPE phase and adding PEA effectively enhanced the interaction between UHMWPE and ATSP.     

试验参数对人工滑液边界润滑条件下超高分子量聚乙烯/Ti6Al4V往复摩擦磨损行为的影响

采用自行研制的往复摩擦磨损试验机,在法向载荷50 N、往复频率1 Hz、摩擦副接触形式为圆环外圆周/平面、初始线接触长度为6 mm、相对湿度为80%的试验条件下,研究了钛合金表面粗糙度、试验环境温度、试验延续时间、滑液成分等试验参数对UHMWPE/Ti6A14V摩擦副的往复摩擦磨损行为的影响.结果表明,这些试验参数均显著影响UHMWPE/Ti6A14V摩擦副的往复摩擦磨损行为;在环境温度20℃、25%小牛血清去离子水溶液边界润滑、180 min往复摩擦磨损试验条件下,当钛合金表面粗糙度由Ra0.04 μm增加至Ra0.06μm时,摩擦副的平均摩擦因数由0.033增加至0.096,UHMWPE试样磨损量由0.131 mm3,增加至0.149 mm3;在钛合金表面粗糙度为Ra0.06μm、25%小牛血清去离子水溶液边界润滑、180 min往复摩擦磨损试验条件下,当试验环境温度由10℃上升至37℃时,摩擦副的平均摩擦因数由0.135减少至0.077,UHMWPE试样磨损量由0.188 mm3减少至0.134 mm3.     

Effect of Water and Serum Absorption on Wear of Unirradiated and Crosslinked UHMWPE Orthopedic Bearing Materials

Abstract

In addition to confounding mass-based wear measurements in serum-lubricated hip simulator experiments, fluid absorption by the acetabular cups may simultaneously modify the wear resistance of the ultra-high molecular weight polyethylene (UHMWPE) from which they are composed. To decouple the fluid absorption and wear processes enabling clearer investigation of this effect, absorption was first imposed during an initial stage where UHMWPE was exposed to pressurized (10 MPa) fluid. This was followed by a second stage, where resultant wear behavior was assessed by a multidirectional pin-on-flat technique that, though still providing a serum-lubricating environment, does not promote the simultaneous fluid absorption occurring in hip simulator testing. Both unirradiated and highly crosslinked UHMWPE were investigated, each with both bovine calf serum and water soaking exposures of duration to 129 days. The pressurized soaking of a highly crosslinked UHMWPE decreased its wear resistance, causing an increase in wear rate by approximately 50% during subsequent serum-lubricated multidirectional pin-on-flat sliding tests as compared to non-soaked material. The magnitude of this effect did not appear to depend on whether the soaking fluid was water or serum, nor did it appear to depend on soak time provided it was at least of a 14-day duration, during which more rapid transient fluid absorption occurs. Such soaking did not produce as pronounced an effect on unirradiated UHMWPE, as its lack of wear resistance likely causes the absorption-affected surface region to be removed within the earliest stages of sliding contact.     

Pre-Polishing the Metal Counterface of Metal–UHMWPE Wear Pair with Filler-Filled UHMWPE Composites to Generate Counterface Changes for an Effective Reduction in Pure UHMWPE Wear

Ultra-high molecular weight polyethylene (UHMWPE) is well known for high-wear-resistance applications. Its long-chained easy sliding molecules and semi-crystalline structures enable the polymer’s great wear resistance. UHMWPE composites made for higher wear resistance study have been analyzed in this paper. Pure UHMWPE, 1 wt% CNT UHMWPE, 1 wt% PEEK UHMWPE, 1 wt% alumina (nano)–UHMWPE composites were made to be tested against metal disk on pin-on-disk tribometer. The metal disk surface conditions were found to have significant influence on the UHMWPE–polymer wear than the composite itself. This result indicates a simple and industrial applicable method that involves transfer film on the counterface to reduce polymer wear for metal–polymer wear pair applications.     

Pattern abrasion of ultra-high molecular weight polyethylene: Microstructure reconstruction of worn surface

The friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against bearing steel (AISI 52100) in a ring-on-block contact mode under the lubrication of aqueous solution of 3.5% NaCl was evaluated. The worn polymer surfaces were analyzed by means of three dimensional profiling, atomic force microscopy, Polarized Raman microanalysis, field emission scanning electron microscopy, and nanoindentation testing. It was found that unusual wavelike abrasion patterns were formed on the worn surface of UHMWPE under properly selected sliding conditions. In the presence of plowing effect, the molecular chains of UHMWPE and short-rod like microcrystalline grains of abrasion pattern were both further oriented along the plowing direction and became tiny and dense owing to microstructure reconstruction. Resultant microstructurally reconstructed worn surface of UHMWPE had a higher nanoindentation hardness and modulus as well as increased wear resistance.     

Tribological behaviour of plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE

A detailed study has been made on the wear behaviour of untreated and plasma nitrided Ti-5Al-2Nb-1Ta orthopaedic alloy against ultra high molecular weight polyethylene (UHMWPE) using pin on disc tribometer under lubricated conditions. The effects of nitriding temperature and nitriding time on the basis of the evolution of the wear volume loss and friction coefficient were investigated. The wear resistance of the plasma nitrided alloys increased considerably when compared to the untreated alloy. The wear debris identified using X-ray diffraction measurements indicated the formation of titanium oxide and titanium oxynitride particles. The wear rate was found to increase with increase in load and sliding velocity.     

Reduction of total knee replacement wear with vitamin E blended highly cross-linked ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) is a common bearing component in total knee replacement (TKR) implants, and its susceptibility to wear continues to be the long-term limiting factor in the life of these implants. This study hypothesized that in TKR systems, a highly cross-linked (HXL) UHMWPE blended with vitamin E will result in reduced wear as compared to a direct compression-moulded (DCM) UHMWPE. A wear simulation study was conducted using an asymmetric lateral pivoting '3D Knee' design to compare the two inserts. The highly cross-linked UHMWPE was aged prior to the testing and force-controlled wear testing was carried out for 5 million cycles using a load-controlled ISO-14243 standard at a frequency of 1 Hz on both groups. Gravimetric measurements of DCM UHMWPE (4.4 +/- 3.0 mg/million cycles) and HXL UHMWPE with vitamin E (1.9 +/- 1.9 mg/million cycles) showed significant statistical differences (p < 0.01) between the wear rates. Wear modes and surface roughness for both groups revealed no significant dissimilarities.     

Experimental analysis of tribological behavior of UHMWPE against AISI420C and against TiAl6V4 alloy under dry and lubricated conditions

Friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against AISI420C austenitic stainless steel and against TiAl6V4 alloy under dry and lubricated conditions were investigated with a reciprocating pin-on-flat tribometer for comparative purposes. The tests were conducted by varying frequency of the pin alternative motion and the applied normal load. For the tests in lubricated conditions a fluid containing a large amount of sodium hyaluronate has been chosen. By using an electronic precision balance the wear mass loss of the UHMWPE samples was evaluated accordingly. Friction is greatly reduced by the presence of UHMWPE and this is believed to be due to the formation of a lubricating film of UHMWPE in the contact zone. Furthermore, the experimental investigation shows that the AISI420C/UHMWPE gives, in dry conditions, better values in the wear rate and in the friction coefficient than the TiAl6V4/UHMWPE.     

纳米颗粒TiO2和SiO2对碳纤维/超高分子量聚乙烯复合材料力学和摩擦学性能的影响

采用UMT-5型摩擦磨损试验机和万能材料试验机考察TiO_2和SiO_2两种纳米颗粒对碳纤维(CF)/超高分子量聚乙烯(UHMWPE)复合材料摩擦学性能和力学性能的影响,利用扫描电镜观察复合材料断面形貌和磨痕表面形貌。结果表明:纳米TiO_2和SiO_2的加入可以改善碳纤维与树脂之间的界面结合强度,从而改善了CF/UHMWPE复合材料的力学性能;在3种复合材料中,纳米TiO_2增强复合材料具有最好的耐磨性。纳米TiO_2和SiO_2的加入可以有效地分散碳纤维表面的应力集中,从而可以改善复合材料的耐磨性,使得CF/UHMWPE复合材料的磨损机制由严重的塑性变形变为轻微的塑性变形。     

Effect of UHMWPE Microparticles on the Tribological Performances of High-Strength Glass Fabric/Phenolic Laminate Composites Under Water Lubrication

The tribological behaviors of ultra-high molecular weight polyethylene (UHMWPE) microparticle-modified high-strength glass fabric/phenolic laminate composites sliding against stainless steel under water lubrication have been investigated. Results showed that the incorporation of UHMWPE microparticles, especially at the mass fraction of 5.0 %, improved the wear resistance of the laminate composite to a significant extent, because UHMWPE microparticle can effectively absorb and dissipate the friction energy through a plastic deformation during the formation of the regular ripple-like abrasion patterns on its worn surface. During the sliding process, after the phenolic resin was firstly worn off, UHMWPE microparticles with much better wear resistance were protruded from the worn surface of the laminate composite, leading to a fundamental change in the contact status of the matched surfaces from rigid resin and fibers/steel to flexible UHMWPE/steel. As a result, low and steady friction coefficient was obtained due to good adaptability of UHMWPE to water lubrication.     

UHMWPE Hybrid Nanocomposites for Improved Tribological Performance Under Dry and Water-Lubricated Sliding Conditions

To tap the full potential of polymers to be used as tribo-materials under water lubrication, it is very important to improve their resistance to water uptake on the one hand and improve their strength and load bearing capacity on the other so that their performance under these conditions is not deteriorated. Hence, a unique approach of fabricating a hybrid polymer nanocomposite reinforced with nanoclay for improving the resistance to water uptake and carbon nanotubes (CNTs) to improve the mechanical/tribological properties is undertaken. Ultrahigh molecular weight polyethylene (UHMWPE) hybrid nanocomposites were fabricated via ball milling followed by hot pressing method. Functionalized multi-wall CNTs and C15A organoclay were used as nanofillers in UHMWPE matrix. Hybrid nanocomposites were developed with CNT loadings of 0.5, 1.5 and 3.0 wt% while keeping C15A organoclay content fixed at an optimized value of 1.5 wt%. Initially, the hybrid nanocomposites were optimized under dry sliding conditions whereby a loading of 1.5 wt% of CNTs and 1.5 wt% C15A organoclay resulted in the maximum reduction in the specific wear rate by about 64% as compared to pristine UHMWPE. Later, tribological performance of the optimized hybrid nanocomposite was compared with pristine UHMWPE and its UHMWPE nanocomposites under water-lubricated conditions sliding against a 440C stainless steel ball for 150,000 cycles. The specific wear rate showed a reduction by ~46% for the 1.5 wt% CNTs hybrid nanocomposites as compared to pristine UHMWPE under water lubrication. The improved resistance to wear was attributed to the uniform dispersion of both the nanofillers, namely CNTs and C15A organoclay which effectively increased the load bearing capacity of UHMWPE. Moreover, the excellent barrier properties of the platelet-like structure of C15A clay which presented a torturous path for the diffusion of the water molecule in UHMWPE reduced the softening of the surface layer leading to better resistance to wear under water lubrication.     

超高分子量聚乙烯材料的边界润滑特性研究

在研究人工关节材料超高分子量聚乙烯(Ultra-high Molecular Weight Polyethylene，UHMWPE)磨损机理时，考虑了表面载荷引起的变形和应力状态，运用有限元技术，采用液-力耦合方法，分析了组织液对裂纹扩展的影响以及骨移植后接触磨损机理。结果表明：裂纹顶部区域符合线弹性断裂机理，这有助于更好地了解骨移植后接触区的磨损机理。     

Nanoindentation properties of compression-moulded ultra-high molecular weight polyethylene

This paper investigates the elastic modulus and hardness of untreated and treated compression-moulded ultra-high molecular weight polyethylene (UHMWPE) tibial inserts of a total knee replacement (TKR) prosthesis. Investigations were carried out at a nanoscale using a Nanoindenter at penetration depths of 100,250 and 500 nm. The nanomechanical properties of surface and subsurface layers of the compression-moulded tibial inserts were studied using the untreated UHMWPE. The nanomechanical properties of intermediate and core layers of the compression-moulded tibial insert were studied using the cryoultrasectioned and etched UHMWPE treated samples. The cryoultrasectioning temperature (-150 degrees C) of the samples was below the glass transition temperature, Tg (-122 +/- 2 degrees C ), of UHMWPE. The measurement of the mechanical response of crystalline regions within the nanostructure of UHMWPE was accomplished by removing the amorphous regions using a time-varying permanganic-etching technique. The percentage crystallinity of UHMWPE was measured using differential scanning calorimetry (DSC) and the Tg of UHMWPE was determined by dynamic mechanical analysis (DMA). Atomic force microscopy (AFM) was used to assess the effect of surface preparation on the samples average surface roughness, Ra. In this study, it was demonstrated that the untreated UHMWPE samples had a significantly lower (p < 0.0001) elastic modulus and hardness relative to treated UHMWPE cryoultrasectioned and etched samples at all penetration depths. No significant difference (p > 0.05) in elastic modulus and hardness between the cryoultrasectioned and etched samples was observed. These results suggest that the surface nanomechanical response of an UHMWPE insert in a total joint replacement (TJR) prosthesis is significantly lower compared with the bulk of the material. Additionally, it was concluded that the nanomechanical response of material with higher percentage crystallinity (67 per cent) was predominantly determined by the crystalline regions within the semi-crystalline UHMWPE nanostructure.     

Comparative study of micro- and nano-ZnO reinforced UHMWPE composites under dry sliding wear

This is a comparative study between ultra-high molecular weight polyethylene (UHMWPE) reinforced with micro-zinc oxide (ZnO) and nano-ZnO under different filler loads. These composites were subjected to dry sliding wear test under abrasive conditions. The micro- and nano-ZnO/UHMWPE composites were prepared by using a hot compression mould. The wear and friction behaviours were monitored using a pin-on-disc (POD) test rig. The pin-shaped samples were slid against 400 grit SiC abrasive papers, which were pasted, on the stainless steel disc under dry sliding conditions. The worn surfaces and transfer film formed were observed under the scanning electron microscope (SEM). Experimental results showed that UHMWPE reinforced with micro- and nano-ZnO would improve the wear behaviour. The average coefficient of friction (COF) for both micro- and nano-ZnO/UHMWPE composites were comparable to pure UHMWPE. The weight loss due to wear for nano-ZnO/UHMWPE composites are lower compared to micro-ZnO/UHMWPE and pure UHMWPE. The optimum filler loading of nano-ZnO/UHMWPE composites is found to be at 10 wt%. The worn surface of ZnO/UHMWPE composites shows the wear mechanisms of abrasive and adhesive wear. Upon reinforcement with micro- and nano-ZnO, the abrasive and adhesive wear of worn surfaces transited from rough to smooth.     

Effect of Compatibilization on Reciprocating Frictional Behavior of Polyamide 66/UHMWPE Blends

The effect of compatibilization on the reciprocating frictional behavior of a polyamide 66 (PA66)/ultra-high molecular weight polyethylene (UHMWPE) blend was investigated. The influence of the amount of added maleic anhydride–grafted polyethylene (MAH-g-HDPE) on the phase morphology, compatibility, and viscoelasticity was explored using scanning electric microscopy (SEM), dynamic mechanical analysis (DMA), and capillary rheometry. In addition, the effect of MAH-g-HDPE on the reciprocating friction and wear performance of the PA66/UHMWPE blend was tested. The worn surface, transfer film, and wear debris were analyzed using SEM, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results showed that the maleic anhydride groups in the MAH-g-HDPE improved the compatibility of PA66 and UHMWPE, and the addition of MAH-g-HDPE enhanced the interface bonding strength and lowered the polar difference between PA and UHMWPE. Therefore, the improved compatibility enhanced the wear resistance of the blend. During reciprocating sliding, UHMWPE transferred to the counterface prior to PA66 for the incompatible blend. The addition of MAH-g-HDPE promoted the adhesion and transfer of PA66 to the counterface.