偏苯三酸酯基础油的摩擦降解及对抗氧化性能的影响

为研究润滑油在边界润滑条件下的摩擦降解及其对润滑油性能的影响,采用四球试验机考察偏苯三酸三异辛醇酯(TMTO)、偏苯三酸三异壬醇酯(TMTD)以及偏苯三酸三异十三醇酯(TMTT)在边界润滑条件下的摩擦学性能。结果表明:分子结构对偏苯三酸酯在边界润滑条件下的润滑性能有较大影响,链长最长的TMTT的减摩与抗磨性能优于TMTO与TMTD。利用高压差示扫描量热仪(PDSC)及热重分析仪(TGA)研究四球试验前后3种基础油的抗氧化性能及热分解性,并测试摩擦试验前后润滑油的黏度与酸值变化。结果表明:边界润滑条件下的摩擦过程会导致偏苯三酸酯类基础油黏度升高、酸值降低、氧化安定性下降;润滑性能良好的基础油在一定程度上阻止或减缓润滑油本身氧化反应的发生;在边界润滑条件下,偏苯三酸酯一部分在机械剪切及水解作用下分解会生成小分子的化合物,另一部分在氧化作用下聚合生成大分子化合物。

在甘油润滑下TiAlN涂层的超低摩擦和磨损特性

TiAlN涂层具有优异的力学性能,在刀具领域具有广泛的应用背景,然而优化制备参数以获得性能更为优异的TiAlN涂层仍需要做进一步的研究,同时与TiAlN涂层相适应的绿色润滑剂也是当前亟待解决的问题之一。基于磁控溅射技术,研究Al靶溅射电流对TiAlN涂层结构和力学性能的影响,考察甘油润滑下TiAlN涂层的摩擦学性能,并利用X射线光电子能谱探究甘油的润滑机理。结果表明:当溅射电流为3 A时得到的TiAlN-3A涂层具有最致密的晶状结构及最优的力学性能。在甘油润滑下,TiAlN-3A涂层的摩擦因数仅为0.007,其磨损率为2.62×10^(-6)mm^(3)N^(-1)m^(-1)。XPS分析表明,甘油在钢球与TiAlN涂层相对滑动过程中发生摩擦降解反应,在表面上生成新的产物FeOOH。FeOOH的亲水性使得在接触区域表面吸附甘油分子及甘油降解产物形成流体润滑层,可提供优异的减摩和耐磨性能。

Mechanical properties,corrosion behavior and biocompatibility of orthopedic pure titanium−magnesium alloy screw prepared by friction welding

The dissimilar joining of biodegradable magnesium alloy to pure commercial titanium by rotational friction welding with rotational speeds of 1100,1200 and 1300 r/min for the production of bio-screw was investigated.The metallographic analysis revealed that a good joining was obtained at the Ti/Mg alloy joint.On the magnesium alloy side,various regions such as the weld center zone(WCZ),dynamic recrystallization zone(DRX),thermo-mechanically affected zone(TMAZ)and partially deformed zone(PDZ)were observed.The highest tensile and shear strengths were 173 and 103.2 MPa,respectively at a rotational speed of 1300 r/min.The Ti/Mg alloy dissimilar friction welded joint failed at the vicinity of the intermetallic zone containing Ti3Al phase.The hardness values from the base metal magnesium alloy to the joining point increased mainly due to grain refinement(8.57μm in diameter)and the presence of titanium particles,while the hardness values were constant on the titanium side.It was also found that the corrosion rate of the Ti/Mg alloy joint was higher compared with that of the Ti and Mg alloy from the immersion studies.Additionally,the sample with a rotational speed of 1300 r/min showed better biocompatibility and a cell viability of 98.12%due to better corrosion resistance.