Tribology Letters 

About: Tribology Letters is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Tribology & Lubrication. It has an ISSN identifier of 1023-8883. Over the lifetime, 3474 publications have been published receiving 92617 citations.

The History and Mechanisms of ZDDP

Abstract: This paper reviews research into the mechanisms of action of the lubricating oil additive, zinc dialkyldithophosphate (ZDDP). The development of the use and research into ZDDP is first charted historically, starting with the additive's first introduction in engine oils in the late 1930s. Then our current state of knowledge of each of the main facets of ZDDP behaviour both in solution and at metal surfaces is identified and discussed. It is concluded that we now know a great deal about the properties and morphology of ZDDP antiwear films but still relatively little about the reaction pathways that lead to ZDDP film formation or about the kinetics of ZDDP film generation and removal.

A Raman Spectroscopic Study of MoS2 and MoO3: Applications to Tribological Systems

Abstract: Molybdenum disulfide (MoS2) and molybdenum trioxide are investigated using Raman spectroscopy with emphasis on the application to tribological systems. The Raman vibrational modes were investigated for excitation wavelengths at 632.8 and 488 nm using both micro-crystalline MoS2 powder and natural MoS2 crystals. Differences are noted in the Raman spectra for these two different wavelengths, which are attributed to resonance effects due to overlap of the 632.8 nm source with electronic absorption bands. In addition, significant laser intensity effects are found that result in laser-induced transformation of MoS2 to MoO3. Finally, the transformation to molybdenum trioxide is explored as a function of temperature and atmosphere, revealing an apparent transformation at 375 K in the presence of oxygen. Overall, Raman spectroscopy is an useful tool for tribological study of MoS2 coatings, including the role of molybdenum trioxide transformations, although careful attention must be given to the laser excitation parameters (both wavelength and intensity) when interpreting Raman spectra.

Improving Tribological Performance of Mechanical Components by Laser Surface Texturing

Abstract: Significant improvement in load capacity, wear resistance, friction coefficient etc. of tribological mechanical components can be obtained by forming regular micro-surface structure in the form of micro-dimples on their surfaces. A feasibility study was performed both theoretically and experimentally using the Laser Surface Texturing (LST) technique to produce the micro-dimples. Each micro-dimple can serve either as a micro-hydrodynamic bearing in cases of full or mixed lubrication or as a micro-reservoir for lubricant in cases of starved lubrication conditions. Theoretical models were developed, and laboratory tests were performed, to investigate the potential of LST in tribological components like mechanical seals, piston rings and thrust bearings. In the entire laboratory tests, friction was substantially reduced with LST compared to the non-textured components.

Aluminum Metal-Matrix Composites for Automotive Applications: Tribological Considerations

Abstract: Aluminum alloys possess a number of mechanical and physical properties that make them attractive for automotive applications, but they exhibit extremely poor resistance to seizure and galling. Reinforcement of aluminum alloys with solid lubricants, hard ceramic particles, short fibers and whiskers results in advanced metal-matrix composites (MMC) with precise balances of mechanical, physical and tribological characteristics. Advanced manufacturing technologies such as squeeze infiltration of molten alloys into fiber performs can be employed to produce near net-shape components. Brake rotors, pistons, connecting rods and integrally cast MMC engine blocks are some of the successful applications of Al MMCs in automotive industry. This paper gives an overview of the tribological behavior of Al MMCs reinforced with hard particles, short fibers, and solid lubricants, and the technologies for producing automotive parts from these novel materials.

Modification of Graphene Platelets and their Tribological Properties as a Lubricant Additive

Abstract: Graphene platelets were chemically modified in a reflux reaction with stearic and oleic acids. Examination of the surface features of the graphene platelets before and after modification by infrared spectroscopy and ultraviolet–visible spectrophotometer revealed that the modification led to an improvement in the dispersion of graphene platelets in base oil. The tribological behavior of the lubricating oil containing modified graphene platelets (MGP) was further investigated using a four-ball machine. The results indicated that the oil containing only 0.075 wt% of MGP clearly improved the wear resistance and load-carrying capacity of the machine. Scanning electron microscopy and energy dispersive spectrometer performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of MGP could be attributed to their small size and extremely thin laminated structure, which allow the MGP to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.