Wear assessment of a Ti–6Al–4V motion-preserving porous artificial-cervical-joint fabricated by SLM after surface carburization

Adjacent segment degenerative diseases are a major clinical concern for anterior cervical corpectomy with fusion surgery. In this study, a hybrid motion-preserving cervical prosthesis consists of two articulating joints and one porous fusion body is designed to provide motion ability and reduce the occurrence of degenerative diseases. The hybrid design is fabricated from Ti–6Al–4V (TC4) alloy using selective laser melting (SLM) technology. After carburization pretreatment, two types of bearing couple SLM-TC4 self-mating and SLM-TC4/UHMWPE were studied in terms of lubrication regime, contact mechanics and wear performance. According to the ISO 18192-1 standard, five million cycles (Mc) of in vitro spine simulator wear tests were conducted in bovine serum lubricated condition.Hamrock-Dawson minimum lubrication film thickness analysis stated that both bearing was likely under boundary lubrication only, with extensive surface asperities contact. And, the contact stress encountered during in vitro condition was not enough to cause surface fatigue failure of any bearing couple. In term of wear performance, the obtained steady state wear rates were 0.160 ± 0.004 mm³/Mc for SLM-TC4 self-mating and 8.57 ± 0.06 mm³/Mc for SLM-TC4/UHMWPE bearing couples, respectively. According to these outcomes, SLM-TC4 self-mating couple was more promising for the articulating joint bearing design.For SLM-TC4 self-mating couple, the initial wear mechanism was abrasion with potential third-body abrasion wear. As the wear cycle proceeding, the TiC cermet layer was gradually damaged and exposed the local bare metal. Under this circumstance, material loss was consisted of abrasion wear, adhesion wear, and tribo-corrosion. In comparison, the wear mechanism of SLM-TC4/UHMWPE bearing was always abrasion-adhesion of UHMWPE. The surface of UHMWPE socket was severely plowed by the hard micro bulge of the TiC layer, and material loss and plastic deformation occurred only on the UHMWPE socket. In conclusion, carburization pre-treatment causes a hard TiC cermet layer formation on the SLM-TC4, which enhance its hardness and protect underling material from corrosion damage. The thickness and quality of the TiC layer directly affect the longevity of the joint prosthesis in vivo.     

纳米Al_2O_3填充超高分子量聚乙烯的生物摩擦磨损性能研究

用纳米Al2O3对人工关节软骨UHMWPE进行填充改性,在生理盐水润滑条件下,评价了其摩擦磨损性能。结果表明,纳米Al2O3的加入,在一定程度上提高了UHMWPE的硬度,与钛合金对磨时的摩擦系数随Al2O3含量(<10%)的增加而增加;与不锈钢对磨时,摩擦系数有所增加;不同Al2O3含量(<10%)的UHMWPE,磨损率比纯UHMWPE低。纯UHMWPE的磨损表现为明显的犁沟以及塑性变形,加入纳米Al2O3的UHMWPE的磨损主要表现为磨粒磨损和轻微的塑性变形。     

UHMWPE用于生物工程的摩擦磨损研究

世界各国一般都采用UHMWPE作人工关节假体中的髋臼材料，人工关节松动的主要原因是UHMWPE的细小磨损颗粒引起骨溶解致使假体松动。为了研究髋臼材料的耐磨性，减少磨损颗粒的产生，笔者对国内分子量最高（497万）的UHMWPE模压成型试样和机加工成型试样的表面摩擦磨损性能进行了研究。此外，还研究了分子量对UHMWPE磨损量的影响以及UHMWPE在生理盐水润滑下的摩擦性能。     

Characteristic modeling of the wear particle formation process from a tribological testing of polyethylene with controlled surface asperities

To study the ultra‐high molecular weight polyethylene (UHMWPE) wear particles‐induced osteolysis which leads to the failure of artificial joints, microfabricated surfaces with controlled asperities have been applied to generate narrowly distributed UHMWPE wear particles with various sizes and shapes. Our previous study further facilitated single wedge sliding tests to investigate the mechanism of the UHMWPE particle generation. In this study, the attempt was made to characterize the particle generation process into a mathematical model to predict particle volume with a given surface‐texture dimensions and mechanical loading conditions. The particle‐generation process is decomposed into two steps: (1) penetration of the cutting edge, and (2) lateral sliding of the cutting edge. By combining the indentation experimental data, the viscoelastic responses of UHMWPE was incorporated in the model. The effects of normal load, feature height, and cutting edge angle on the wear particle volume were illustrated from model predictions. Both experimental results and model predictions indicate the same trend of effects of surface‐texture geometry and mechanical conditions on the volume of particles. The results of the model predictions are close to the experimental results of the particle generation. However, the particle volume predicted by the model is larger than the experimental results. It is believed that the reprocessing of the generated particles and viscoelastic recovery of UHMWPE in the experiments account for this difference. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 587–594, 2007     

试验环境温度对小牛血清边界润滑条件下超高分子量聚乙烯往复磨损行为的影响

采用自行研制的往复摩擦磨损试验机,在法向栽荷为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%、体积含量25%小牛血清去离子水溶液边界润滑的试验条件下,研究试验环境温度对超高分子量聚乙烯(UHMWPE)与铁合金配副的往复摩擦磨损性能的影响,并利用扫描电子显微镜观察37℃时磨损表面形貌.结果表明:试验环境温度θ由10℃升高至30℃,UHMWPE/钛合金摩擦副的平均摩擦因数μa呈明显下降趋势,由30℃升高至37℃时,μa开始缓慢上升,UHMWPE的体积磨损量Wv随试验环境温度θ变化也呈现相似的规律;磨损机制主要表现为磨料磨损.     

Friction and wear properties of graphene oxide/ultrahigh‐molecular‐weight polyethylene composites under the lubrication of deionized water and normal saline solution

Ultrahigh‐molecular‐weight polyethylene (UHMWPE) and UHMWPE composites reinforced with graphene oxide (GO) were successfully fabricated through a new step of liquid‐phase ultrasonic dispersion, high‐speed ball‐mill mixing, and hot‐pressing molding technology. When the GO/UHMWPE composites were lubricated with deionized water (DW) and normal saline (NS) solution, their friction and wear properties were investigated through sliding against ZrO₂. The worn surface and wear volume losses of these composites were studied with scanning electron microscopy, X‐ray photoelectron spectroscopy, and a Micro‐XAM 3D non‐contact surface profiler. The results show that the microhardness of the GO/UHMWPE composites was improved by 13.80% and the wear rates were decreased by 19.86 and 21.13%, whereas the depths of the scratches were decreased by 22.93 and 23.77% in DW and NS lubricating conditions, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39640.     

Tribological behaviour of a 3Y-TZP/Ta ceramic-metal biocomposite against ultrahigh molecular weight polyethylene (UHMWPE)

This study aims to evaluate the tribological behaviour of 3Y-TZP/Ta (20 vol%) ceramic-metal composites and 3Y-TZP monolithic ceramic prepared by spark plasma sintering (SPS) against ultrahigh molecular weight polyethylene (UHMWPE). According to the results of pin (UHMWPE)-on-flat wear test under dry conditions, the UHMWPE – 3Y-TZP/Ta system exhibited lower volume loss and friction coefficient than the UHMWPE – monolithic ceramic combination due to the presence of an autolubricating layer that provides sufficient lubrication for reducing the friction. Owing to the lubrication of the liquid media, under wet conditions obtained using simulated body fluid (SBF), similar behaviour is observed in both cases. Additionally, the ceramic and biocomposite materials were subjected to a low temperature degradation (LTD) process (often referred to as “ageing”) to evaluate the changes in the tribological behaviour after this treatment. In this particular case, the wear properties of the UHMWPE-biocomposite system were found to be less influenced by ageing in contrast to the case of the UHMWPE-zirconia monolithic material. In addition to their exceptional mechanical performance, 3Y-TZP/Ta composites also showed high resistance to low temperature degradation and good tribological properties, making them promising candidates for biomedical applications, especially for orthopaedic implants.     

纳米氟化镧对生物质燃油碳烟颗粒流润滑特性影响

为探索极端乏油工况下碳烟颗粒在发动机摩擦副界面的功效及润滑油添加剂的作用,本文采用往复摩擦磨损试验机研究了纳米氟化镧（nano-LaF₃）颗粒对往复滑动条件下生物质燃油碳烟（BS）颗粒流润滑性能的影响。借助拉曼光谱仪、3D激光扫描显微镜、X射线光电子能谱仪等仪器探讨了滑动条件下nano-LaF₃对BS颗粒流润滑特性的影响作用机理。结果表明：当nano-LaF₃的添加质量分数大于20%时能显著改善往复滑动条件下BS颗粒的抗磨减摩性能,并且随着nano-LaF₃添加浓度的增大,摩擦表面碳烟石墨化程度和石墨微晶尺寸均增大。nano-LaF₃在含BS颗粒流润滑的摩擦界面形成了LaF₃摩擦膜以及含镧化合物、碳氧化合物及铁氧化合物的化学复合反应膜,同时nano-LaF₃会加大诱导碳烟的石墨化作用,从而增强了BS颗粒流润滑的减摩性。     

On the efficiency of internal lubricants for polymers under different sliding conditions

When polymers are used as bearing materials or are processed over tooling under dry sliding conditions, the formation of a transfer layer at the interface controls friction and wear properties. The film formation may be enhanced by the addition of internal lubricants. This article reviews some effects of internal lubricants, such as graphite, polytetrafluoroethylene, and internal silicone oil, on the friction and wear of bulk polymers such as polyimide, polyester, and polyamide. Known lubricating mechanisms are complemented by an interpretation of tribophysical reactions in the sliding interface. Test results are obtained during small and large‐scale laboratory testing under high‐load and high‐temperature conditions and are further related to the effect of contact conditions. The study reveals that some lubricants are not effective under the entire range of sliding temperatures and/or normal loads. For internally lubricated polymers, the efficiency of internal lubricants strongly depends on the contact geometry. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

A study on sliding wear of ultrahigh molecular weight polyethylene/polypropylene blends

The wear and friction behavior of ultrahigh molecular weight polyethylene (UHMWPE)/ polypropylene (PP) blends was studied. The addition of PP improves processability and the anti‐wear properties of UHMWPE. The friction coefficient and wear rate of pure UHMWPE are much higher than those of UHMWPE/PP blends under the same conditions, and the wear rate of UHMWPE is more sensitive to load and wear time than that of the UHMWPE/PP blend. Long scratch grooves and cracks occurred in the worn surface of UHMWPE, while no such serious damage was observed in the worn surface of the UHMWPE/PP blend. Atomic Force Micrograph using the contact mode indicated that the friction force between pure UHMWPE and Si₃N₄ tip is much higher than that for the UHMWPE/PP blend, which is consistent with the results from macro‐friction testing.     

Effects of lubricating‐oil additives on the friction and wear properties of polymers and their composites sliding against steel under oil‐lubricated conditions

The effects of lubricating‐oil additive zinc dialkyldithiophosphate (ZDDP) on the friction and wear properties of polymers and their composites sliding against GCr15 bearing steel were studied by using an MHK‐500 ring‐on‐block wear tester (Timken wear tester). Then the frictional surfaces of the friction pairs were examined by using electron probe microanalysis (EPMA). Experimental results show that the ZDDP contained in liquid paraffin has little effect on the friction coefficients of the polyimide (PI) or polyamide 66 (PA66) against GCr15 bearing steel friction pairs compared with that under the lubrication of liquid paraffin, but it slightly reduces the friction coefficients of polytetrafluoroethylene (PTFE) or its composites against GCr15 bearing steel friction pairs. Under lubrication of liquid paraffin containing 2 wt % ZDDP, the ZDDP film absorbed on the frictional surfaces of the PTFE composites–GCr15 bearing steel friction pairs exhibits obvious antiwear properties; it greatly reduces the wear of pure PTFE and the PTFE composites filled with Pb, PbO, and MoS₂; and the wear of the PTFE composites can be reduced by one order of magnitude compared with that under lubrication of pure liquid paraffin. Meanwhile, the inorganic fillers Pb, PbO, and MoS₂ contained in PTFE have little effect on the absorption of ZDDP to the frictional surfaces, so they have little effect on the friction coefficients of the PTFE composites–GCr15 bearing steel friction pairs under the lubrication of liquid paraffin containing 2 wt % ZDDP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1240–1247, 2000     

PCEC hydrogel used on sustained‐release hyaluronic acid delivery with lubrication effect

Injection of bionic synovial fluid (BSF) is a conventional method to improve the lubricity of artificial joints, but BSF cannot maintain long due to the dilution and degradation of BSF in human body. To prolong the effectiveness of hyaluronic acid (HA), which is the major component of BSF, this study applies a temperature‐sensitive poly(?‐caprolactone)–poly(ethylene glycol)–poly(?‐caprolactone) (PCEC) hydrogel loaded with HA to achieve long‐term lubrication. In addition, Fourier transform infrared, nuclear magnetic resonance analysis, X‐ray diffraction, scanning electron microscopy (SEM), and gel permeation chromatography spectra were used to analyze the structure of the synthetic hydrogel. Rheological test and test tube inverting method were used to characterize the thermosensitivity. The lubrication properties of the released solution were characterized by UV–vis, tribological tests, SEM, and 3D laser confocal scanning microscope. The experimental results reveal that the triblock PCEC hydrogel contains both hydrophilic block and hydrophobic block, and both PCEC and PCEC/HA hydrogels have phase‐changed effect when the temperature increases from room temperature to body temperature. Moreover, the friction coefficient of the released solution from PCEC/HA hydrogel is approximatively 38% lower than that of phosphate buffer saline. And the ability of shear resistance and creep recovery of PCEC/HA hydrogel are better than that of PCEC hydrogel. This study provides an effective approach to achieve long‐time lubrication effect for artificial joints. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46228.     

超高分子量聚乙烯的滑动摩擦磨损研究

本文在塑料滑动摩擦磨损试验方法的基础上,研究超高分子量聚乙烯（UHMWPE）与砂纸进行滑动摩擦磨损的过程,为快速、合理的评价UHMWPE板材料、管材料的耐磨性能提供方法。实验过程中,随着摩擦距离改变,UHMWPE的磨损量与磨痕宽度变化明显,而且磨损表面表现出不同的摩擦学特征。另外,摩擦过程生热严重,容易发生氧化反应。通过磨粒磨损、粘着磨损、疲劳磨损等机理对UHMWPE摩擦磨损过程进行了说明。     

润滑剂对Ti（CN）陶瓷摩擦学性能的影响

在销—盘试验机上考察了干摩擦、水润滑及油润滑条件下Ti(CN)/45钢摩擦副的摩擦磨损性能。Ti(CN)陶瓷的磨损主要由粘着剥落和微断裂引起,水对Ti(CN)/45钢摩擦副的摩擦性能无明显改善,但能较明显地减小陶瓷的磨损。油润滑时,摩擦和磨损均得到了明显改善。水和油润滑介质的存在能有效地抑制金属在陶瓷表面的粘着转移,从而降低陶瓷磨损率。采用SEM,XPS,AES等对陶瓷磨痕的分析结果表明,摩擦面上Fe_2O_3的生成对粘着磨损起到了一定的改善作用。油(不含添加剂的液体石蜡)在极压条件下的减磨作用主要是由于其在陶瓷摩擦面上形成了较厚的碳膜(焦质,石墨复合膜)。     

Tribo-material based on a UHMWPE/RGOC biocomposite for using in artificial joints

Reduced graphene oxide (RGOC) filler that was green synthesized by vitamin C had been included in the ultrahigh molecular weight polyethylene (UHMWPE) matrix to produce biocomposite possessing improved properties especially against wear. The biocomposites filled with different loading (0.1, 0.3, 1.0, and 2.0 wt%) of RGOC was produced by a method of liquid phase ultrasonic mixing and then hot press molding. The structural analysis results of biocomposites showed that RGOC well-dispersed in polymer matrix and confirmed that there was interaction between the RGOC-UHMWPE. The biocomposite containing 2.0 wt% RGOC (UHMWPE/RGOC-2) gave the maximum microhardness and the value increased by 22. 5% compared with unfilled polymer. At the same RGOC content, the biocomposite had the highest thermal stability with residue content at 2.42%. The wear and friction behavior of biocomposites were carried out in a reciprocating friction testing machine under distilled water lubricating conditions. The UHMWPE/RGOC-2 biocomposite had the lowest friction coefficient value (0.034) and the wear rate of the biocomposite decreased by 44%, compared with that of unfilled UHMWPE. Furthermore, fatigue wear tracks were significantly reduced. This study suggests the use of this composite that had excellent tribological behavior as biomaterial instead of UHMWPE.     

芳纶浆粕增强丁腈橡胶复合材料的摩擦磨损性能

利用开炼机制备了丁腈橡胶(NBR)/芳纶浆粕(PPTA-pulp)复合材料。研究了在干摩擦和水润滑条件下,纤维含量、摩擦时间以及载荷对NBR/PPTA-pulp复合材料摩擦磨损性能的影响,并分析了磨损机理。结果表明,芳纶浆粕的加入能够很好地改善复合材料的力学性能和摩擦磨损性能,在相同条件下,当纤维质量分数为20%时,复合材料的综合性能最佳;在干摩擦条件下,随着摩擦时间延长,复合材料的摩擦系数下降,磨耗量增大;随着载荷增加,摩擦系数和磨耗量增大;水润滑条件下,复合材料的摩擦系数和磨耗量较干摩擦大幅度降低且比较稳定,时间和载荷对其影响很小;干摩擦时,复合材料的磨损机理主要为磨粒磨损和疲劳磨损;水润滑时,主要为轻微磨粒磨损。     

聚四氟乙烯及其石墨填充复合材料的摩擦磨损特性

对聚四氟乙烯（PTFE）及石墨填充PTFE复合材料在不同载荷、不同润滑条件下,以及在不同对磨时间内的摩擦磨损性能进行了研究。结果表明,石墨填充PTFE的耐磨性比纯PTFE提高很多,不同的润滑条件对PTFE和石墨填充PTFE的磨损量及摩擦系数的影响不一样,对纯PTFE,其磨损量在水润条件下较小,而对石墨填充PTFE,其磨损量在油润滑条件下较小。     

类金刚石薄膜在人工关节摩擦副表面改性进展

类金刚石（DLC）薄膜由于其优异的减摩耐磨性以及良好的生物相容性被引入到人工关节材质中。该文综述了DLC薄膜在人工关节摩擦副表面改性的研究现状,包括DLC薄膜的分类和制备方法。尽管该薄膜已被研究数十年,但在人体复杂的生理力学环境中高负荷摩擦腐蚀等综合作用下,仍存在高内应力导致结合力不足,从而限制其在人工关节领域的应用。该文介绍了降低DLC薄膜内应力提高膜基结合力的方法和DLC薄膜生物相容性的研究进展。最后,对不同DLC薄膜人工关节摩擦副的研究进展进行了阐述。根据该综述,提出厚的无氢DLC涂层（高sp3含量）,且在两个滑动表面上均有DLC薄膜的人工关节副具有优异的耐磨性,对于承重植入体应用至关重要。     

Short aramid-fiber reinforced ultra-high molecular weight polyethylene

Summary Ultra-High Molecular Weight Polyethylene (UHMWPE) is frequently used in artificial joints because of its high wear resistance. To extend the lifetime of these joints even further, it is necessary to decrease the wear rate. The wear rate may be decreased by blending UHMWPE with short aramid fibers. On account of the extremely high viscosity of UHMWPE mixing was accomplished by swirling the UHMWPE powder and the chopped fibers with compressed dry nitrogen, and a composite with fairly uniformly distributed and randomly oriented fibers was obtained by compression moulding. The failure behaviour of the composite changes from ductile for low fiber content to brittle failure for higher fiber content. The deviation of the experimental Young's modulus from the theoretical value can be explained by, among others, the void content. Preliminary results show that the wear rate of UHMWPE indeed decreases with incorporation of the aramid fibers.     

A biomimetic bilayer coating on laser-textured Ti6Al4V alloy with excellent surface wettability and biotribological properties for artificial joints

Titanium alloys with excellent mechanical properties and biocompatibility are widely used in surgical implants. However, due to its poor tribological properties, it is difficult to be used in joint bearing interfaces. Herein, mimicking the soft/hard hierarchical structure of articular cartilage/subchondral bone and the unique lubrication mechanisms of articular cartilage, a biomimetic bilayer coating consisting of a TiO₂ layer and a hydrogel layer was fabricated on laser-textured Ti6Al4V alloy by laser surface texturing, thermal oxidation and ultraviolet radiation techniques. Meanwhile, a zwitterionic polymer (SBMA) was introduced into the hydrogel layer to provide hydration lubrication. The experimental results demonstrated that the introduction of SBMA greatly improved the hydrophilicity and compressive modulus of the hydrogel layer. Compared with Ti6Al4V, the Ti6Al4V-hydrogel bearing interface exhibited a lower friction coefficient (0.06) and better wear resistance when lubricated in deionized water. More importantly, this Ti6Al4V-hydrogel bearing interface could maintain stable and low friction coefficients when lubricated in different physiological solutions for a long-term friction (4 h), and the lowest friction coefficient (0.039) was measured in phosphate buffer (PBS) solution. The outstanding biotribological performance was mainly attributed to the biphasic and hydration lubrication mechanisms of the hydrogel layer. This study provides new insights into the development of Ti6Al4V bearing interfaces for artificial joints.