不同润滑液下的Al_2O_3增强Y-TZP陶瓷/316L不锈钢生物摩擦学特性

采用销-盘式摩擦磨损试验机研究了氧化铝增强氧化锆(ADZ)陶瓷材料/316L不锈钢摩擦副在去离子水和小牛血清2种不同介质润滑下的生物摩擦磨损行为,并利用SEM观察了磨损表面形貌。结果表明:与去离子水相比,在小牛血清润滑条件下ADZ陶瓷的摩擦因数和磨损率降低。在去离子水润滑条件下ADZ陶瓷材料的磨损为轻微磨损,相应的磨损机制为塑性变形和微犁削;而在小牛血清润滑条件下,ADZ陶瓷材料的磨损为微量磨损,磨损过程类似抛光作用。

表面粗糙度对Al_2O_3增强Y-TZP陶瓷材料生物摩擦学特性的影响

采用销-盘式摩擦磨损试验机研究了氧化铝增强氧化锆陶瓷(ADZ)的表面粗糙度对ADZ/316L不锈钢摩擦副的摩擦磨损性能的影响。结果表明:在小牛血清润滑下,随着陶瓷表面粗糙度的降低,ADZ陶瓷和316L不锈钢的摩擦因数和磨损率均呈降低趋势。但是对于表面粗糙度最高的陶瓷,由于Fe转移膜的物理吸附,出现了“负磨损”现象。

A numerical model to simulate the transient frictional viscoelastic sliding contact

Sliding motion has always been one of the major concerns when it comes to the analysis of viscoelastic contact problems.A new model simulating the transient sliding contact of smooth viscoelastic surfaces is developed in this paper.By taking the dry contact friction and the coupling between shear tractions and normal pressure into account,the effect of the early partial slip period,which is often neglected in the study of viscoelastic sliding contact problems,is investigated numerically.Compared with solutions based on the frictionless assumption,the steady-state pressure profile is found to be slightly different under the effect of the partial slip regime,including a lower peak pressure and the shift of the contacting region in the direction opposite to the sliding motion.Furthermore,the time required for the viscoelastic contact to reach its steady state is delayed owing to the partial slip period preceding the global sliding motion.

Comparisons of corrosion behaviour for X65 and low Cr steels in high pressure CO2-saturated brine

Appropriate materials for injection pipelines and tubing for carbon dioxide geologic storage is fundamental to ensure asset integrity and save cost.This paper evaluates the corrosion behaviour of X65,1Cr,3Cr and 5Cr,which have the potential to be injection pipeline/tubing materials.The influence of steel Cr content on the general and localised corrosion behaviour was investigated at time periods from 6 to 192 h at 60℃and 100 bar.The evolution,morphology and chemistry of corrosion products on the surface of each material were evaluated using a combination of scanning electron microscopy,energy dispersive X-ray spectroscopy and X-ray diffraction and related to their overall corrosion protection.Results indicate that prior to the formation of protective films on the steel surfaces,the resistance of the materials to corrosion increase with increasing Cr content(Corrosion resistance:X65<1Cr<3Cr<5Cr).However,as corrosion products evolve,the protection afforded to the different steels significantly varies and decreases with increasing Cr content.×65 becomes the material with the lowest general corrosion rate by the end of the 192 h experiments and 5Cr exhibits the highest corrosion rate(ranking of corrosion resistance:X65>1Cr>3Cr>5Cr).In terms of the corrosion products on X65,both inner amorphous and outer crystalline corrosion layers consist of FeCO3.For the Cr-containing steels,the outer layer also comprises FeCO3,but the inner layer is enriched with Cr,and is predominantly amorphous Cr(OH)3.The extent of localised corrosion(determined using surface profilometry)is noticeably less for X65 compared to the Cr-containing steels.The paper raises questions about the benefits that low Cr steels offer towards extending component design life compared to carbon steel under the test conditions considered here.

Designing soft/hard double network hydrogel microsphere/UHMWPE composites to promote water lubrication performance

Several soft tissues residing in the living body have excellent hydration lubrication properties and can provide effective protection during relative motion.In order to apply this advantage of soft matters in practical applications and try to avoid its disadvantage,such as swelling and weakening in water,a design strategy of a soft/hard double network(DN)hydrogel microsphere modified ultrahigh molecular weight polyethylene(UHMWPE)composite is proposed in this study.A series of microspheres of urea-formaldehyde(UF),polyacrylamide(PAAm)hydrogel,UF/PAAm double network,and their composites were prepared.The mechanical properties,swelling,wettability,friction properties,and the lubrication mechanisms of the composites were investigated.The results show that DN microspheres can have an excellent stability and provide hydration lubrication.The performance of 75 DN-1 composite was superior to others.This finding will provide a novel strategy for the development of water-lubricated materials and have wide application in engineering fields.

Nano-scale coating wear measurement by introducing Raman-sensing underlayer

For gaining fundamental insight into coating wear mechanisms and increasing operational efficiency and automation degree of equipment in important application fields of coating techniques,it is of great importance to developing novel wear measurement techniques enabling nanoscale studies of coating wear in the running process,but this remains a significant challenge.Here,a facile strategy is reported to achieve accurate coating thickness quantification at nanoscale level,which is based on a bilayer structure:a top target layer of a-C:H(hydrogenated amorphous carbon)film is considered as a light attenuating and anti-wear layer while underlayer of silicon serves as Raman-sensing layer.Through constructing the relationship between the thickness of a-C:H and Raman intensity of attenuated silicon signal,the coating thickness quantification method is established and successfully applied to quantify coating wear in the friction process.This approach can effectively avoid remarkable errors caused by tribo-induced effects in the interface regions,demonstrating its advantage in error tolerance.Details about these tribo-induced effects are also elucidated by a combination of Raman spectroscopy,optical profilometer,EELS,and TEM.In particular,the proposed approach enables the possibility of measuring coating wear with oil film on top,which breaks an important limitation of existed wear measurement methods,i.e.,incapable of applying in oil-lubricated conditions.This approach can be used to quantify the wear condition of diverse target coatings and has the potential of online wear monitoring when combining a compact laser excitation and detection system.