The World Tribology Congress 2009 was held under the joint-sponsorship of the Science Council of Japan and the Japanese Society of Tribologists, from Sunday 6th to Friday 11th, September, 2009 at Kyoto International Conference Center, Kyoto, Japan. The papers presented at the World Tribology Congress 2009, and submitted to the Tribology Online have subsequently undergone the normal peer-review process by multiple reviewers.
Tribology Online publishes following five Special Issues —Papers from World Tribology Congress 2009— (WTC 2009 Special Issue).
- WTC 2009 Special issue: Papers form the mini-Symposium on Additives Technology of Lubricants for the Next Generation - WTC 2009 Special issue: Papers form the mini-Symposium on Tribological Aspects of Fluid Power - WTC 2009 Special issue: Papers form the mini-Symposium on History of Tribology - WTC 2009 Special issue: Papers form the mini-Symposium on Hydrogen Tribology for Future Energy - WTC 2009 Special issue: Papers form the Technical Sessions
Each special issue is going to be published as soon as the peer-review and the editorial processes of the papers are finalized.
The mini-Symposium on Additives Technology of Lubricants for the Next Generation was organized by the JAST Technical Committee on Additive Technology for Lubricants, and was held as one of the mini-symposium at the World Tribology Congress 2009. One keynote lecture by Dr. Ardian Morina, University of Leeds, UK, followed by six technical papers were presented at the symposium. Among these presentations, six papers were submitted to the Tribology Online, and they have subsequently undergone the normal peer-review process by multiple reviewers.
On behalf of the Technical Committee, we, the organizers, acknowledge the authors'efforts to submit their papers to this Special Issue. In addition, I would like to express our sincere thanks to the Editors, the Reviewers, and the Publication Coordinators for their effort to complete the peer-review processes and the publication work.
Organizers: Tooru Watanabe and Masabumi Masuko (JAST Technical Committee on Additive Technology for Lubricants)
One of the main challenges that engine oil manufacturers are now facing is to reduce friction losses while at the same time increasing the durability of engine components. New materials are being used for engine components, alongside and to replace conventional ferrous materials. More components are being coated with low friction and highly durable coatings. Lubricants are required to lubricate these surfaces as effectively as conventional materials, with no environmental impact. Knowing that the additive package in today’s lubricants is optimised for lubricating conventional ferrous materials it is of paramount importance to understand how effective the current additives are in lubricating non-ferrous materials. The aim of the current paper is to understand the formation and durability of tribofilms on a Chromium Nitride (CrN) coating formed from two conventional additives; Zinc Dialkyldithiophosphate (ZDDP) and Molybdenum Dialkyl Dithiocarbamate (MoDTC) additives. Tribofilm formation was studied by testing model lubricants containing ZDDP and MoDTC additives on the CrN coating in boundary lubrication, taking the performance on a ferrous system as a reference. The durability was assessed by assessing the tribocouple friction performance in base oil once the tribofilm was formed. Wear scars were fully chemically characterised using X-ray Photoelectron Spectroscopy (XPS). The study shows that the chemical nature of the tribofilms formed on steel and CrN is similar. In both materials, tribofilms were shown to have comparable durability. The factors which affect tribofilm durability and formation, and the reason why ferrous systems and CrN show similarities are discussed.
Due to tightening CO2 emission regulations and increasing fuel prices, fuel economy has become one of the greatest issues facing society today. Although molybdenum dithiocarbamate (MoDTC) is a well-known friction modifier for gasoline engines, it has rarely been applied to a diesel application because of the negative effect soot has on the friction-reducing properties of MoDTC. This study examines which soot properties may influence the friction-reducing attributes of oil containing MoDTC. Fuel consumption tests were also conducted using heavy-duty diesel trucks that met the emission standards of the new long-term Japanese regulations. As a result, a fuel economy improvement of around 2% was observed.
The effects of episulfidation on the frictional properties of mononuclear molybdenum dithiocarbamates having azaheterocycles were investigated. It was shown that the friction coefficients of the lubricants with the episulfided mononuclear molybdenum dithiocarbamates, as measured by the SRV friction test, were lower than those with non-episulfided ones. The friction coefficients of episulfided compounds are also similar to that of binuclear molybdenum dithiocarbamate, which is frequently used as friction modifier in lubricants in actual practice. The extent of decrease in friction in the SRV test differed with the number of carbon atoms in the azaheterocycles of the molybdenum compounds, suggesting that the thermal stability of the compounds affected the friction characteristics of the tested oils. The results from EPMA surface analyses of the disks from the SRV tests suggest that episulfidation of the molybdenum compounds led to effective formation of molybdenum disulfide film by the corresponding oils during the friction tests.
The impact of driveline lubricants on rolling element bearing fatigue has been an important concern for many years. The recent emphasis on improved drivetrain efficiency has further heightened interest in the impact of lubricants on bearing life. A number of laboratory roller bearing test machines have been used to qualify lubricants for automotive applications. Included in these is the Unisteel Rolling Fatigue Testing Machine. We herein present results from an experimental matrix of driveline additives tested using a Unisteel test procedure. Statistical analysis of the cycles to pitting failure suggests that there was no difference in calculated bearing fatigue life between additive families taken as a group. Failure analysis of the end-of-test bearings suggests that the observed fatigue lives were primarily governed by poor surface finish on a flat test specimen commonly used to increase contact stress in accelerated Unisteel bearing fatigue test procedures.
Ever increasing demands on productivity, performance, worker's safety, as well as realization of total cost management lead to new and higher requirements placed on industrial lubricants. Higher machining speeds and new processes may cause much more thermal stress to the whole lubricating system. The paper will focus on comparison of traditional and modern hydraulic additive technology, considering highly refined base oils, compatibility of additive systems as well as widely used specification requirements.
Phenothiazine derivatives have been known to function as antioxidants for engine oils, transmission fluids and industrial lubricants. Alkylated phenothiazines are amines which contain sulfur and have lower bond dissociation energy, i.e. a higher rate constant than their “parent” alkylated diphenylamines. They are highly reactive towards radicals and are therefore excellent inhibitors against autoxidation and polymerisation. Since alkylated phenothiazines can provide superior oxidation stability, help to prolong the useful life of lubricants and significantly improve the durability and resistance of lubricants when exposed to high temperatures, they are of increasing importance. Performance requirements have become more stringent in the past 10 to 20 years and the demand for longer drain intervals has grown steadily. Also, the use of Group II, III and IV base oils is becoming more wide spread. Such base oils have very little sulfur content since natural sulfur-containing antioxidants are either absent or removed during the severe refining process. These evolutions in performance and base oil chemistry can be well handled by the use of phenothiazine chemistry