Optimization of Extreme Load and Break-in Period in Plain ZDDP Oil with FeF3 Catalyst Using Design of Experiment and Fundamental Study under Different Speeds

The mechanism of tribofilm formation and breakdown was carefully followed and studied in 0.1 P% (percentage phosphorus content) plain zinc dialkyldithiophosphate (ZDDP) oil in the presence of iron fluoride (FeF₃) catalyst under extreme Hertzian contact pressure (3.0 GPa) and two different rotational speeds or variable speed with break in period (100 rpm for the first 5,000 revolutions and a 700 rpm until failure or 100,000 revolutions, whichever comes first). At the onset of large frictional fluctuations, the contact surface temperature increased significantly and reached 90°C ± 5°C. The present article describes an innovative method of reducing the surface temperature by using a break in period of 2 or 3 min and rerunning the test until failure. The two different rotational speeds or variable speed will be compared to a steady-state speed of 700 rpm.

Thermal decomposition of ZDDP is examined in the presence of powder and dispersed FeF₃ using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface analyses were carried out using scanning electron microscopy (SEM) coupled with X-ray of the wear tracks, transmission electron microscopy (TEM), and auger electron spectroscopy (AES). Results showed that submicrometer dispersed FeF₃ provided excellent wear protection when combined with ZDDP in the variable-speed test with break-in by forming a tribofilm that is amorphous in nature and rich in phosphorus, which was shown by the TEM and X-ray analyses.     

The Friction and Wear of Metals and Binary Alloys in Contact with an Abrasive Grit of Single-Crystal Silicon Carbide

Sliding friction experiments were conducted with various metals and iron-base binary alloys (alloying elements Ti, Cr, Mn, Ni, Rh, and W) in contact with single-crystal silicon carbide riders. Results indicate that the coefficient of friction and groove height (corresponding to the wear volume) decrease linearly as the shear strength of the bulk metal increases. The coefficient of friction and groove height generally decrease with an increase in solute content of binary alloys. A separate correlation exists between the solute to iron atomic radius ratio and the decreasing rates of change of coefficient of friction and groove height with increasing solute content. These rates of change ate minimum at a solute to iron radius ratio of unity. They increase as the atomic radius ratio increases or decreases linearly from unity. The correlations indicate that atomic size is an important parameter in controlling friction and wear of alloys.     

变频工况下钼类添加剂在润滑脂中的摩擦学性能

在高、中、低频工况下,利用SRV试验机,考察2%T855、2%855+3%T323、2%855+1%TCP、2%855+3%T202四种配方在不同频率下的抗磨减摩性能。结果表明,2%855+3%T202表现出较好的稳定性,在变频工况下抗磨减摩性能优良。对该配方下的实验钢球进行XPS分析,结果表明,在钢球表面有硫、磷、氮和钼元素存在。可以推测出在摩擦副运动的过程中,添加剂与金属表面反应,形成了噻二唑衍生物和硫磷酸盐复合抗磨层,该抗磨层起到了很好的抗磨减摩作用。