Carbon nitride films were grown on silicon and hard disk substrates using pulsed dc magnetron sputtering in a single cathode deposition system. Substrates were mounted on a specially designed rotating holder that allowed 45° tilt angle and substrate rotation about the surface normal up to 20 rpm. AFM scans over 10×10 μm 2 showed that 50 nm thick CN x films prepared under optimum substrate bias conditions have r.m.s. surface roughness almost four times lower than those prepared without substrate tilt and rotation. We observed a two-fold reduction in corrosion damage for hard disk substrates with 1 nm CN x overcoats deposited with substrate tilt and rotation. This improved performance is likely a result of more efficient and uniform momentum transfer parallel to the surface during deposition in this configuration.

Nickel-titanium based superelastic materials are emerging as candidates for rolling element-bearing applications [1]. When properly prepared, these unique intermetallics are hard, exhibit excellent tribological properties and are intrinsically corrosion immune [2]. In addition, recent investigations have revealed that, unlike traditional bearing steels, superelastics can endure much higher levels of recoverable elastic strain during compressive deformation [3]. This behavior enables bearings that are more resilient to load induced damage such as raceway denting and from the ingestion of hard particles. Despite these positive attributes, these alloys differ significantly from conventional steels and these differences must be carefully considered to achieve successful applications. These differences include reduced elastic modulus, high hardness and enhanced resistance to indentation loads. The current paper introduces nickel-titanium based superelastic bearing materials and compares their properties to current bearing materials. General bearing design practices and manufacturing processes are also examined to identify and explore the challenges and opportunities for making resilient rolling element bearings utilizing this new class of superelastic materials.

Selected physical and chemical properties and tribological data for a newly-developed, imidazolium-based ionic liquid (IL) are presented. The IL is soluble in the SAE 5W-30 oil up to a certain weight percentage, and is as a promising candidate for use in lubrication applications, either in its neat version or as an oil additive. Characterization of the IL included dynamic viscosity at different temperatures, corrosion effects on cast iron cylinder liners, and thermal stability analysis. The tribological performance was evaluated using a reciprocating ring-on-liner test arrangement. When used in neat version this IL demonstrated friction coefficient comparable to a fully formulated engine oil, and when used as an oil additive it produced less wear.

An ultrathin (<4 nm) film of amorphous carbon ( a -C) is used in contemporary disk drives to protect the magnetic medium of the hard disk from corrosion and mechanical wear due to intermittent impact of the low-flying magnetic head. Because of increasing demands for much higher magnetic storage densities (i.e., >10 Tbits/in 2 ), the a -C film thickness must be decreased to <2 nm. However, the tribological and mechanical properties of such thin a -C films are not well understood and, moreover, are extremely difficult to determine experimentally. The objective of this study was to obtain insight into the tribological behavior of ultrathin a -C films by performing molecular dynamics (MD) simulations. MD results of the hardness and friction properties of nanometer-thick a -C films are interpreted in terms of the ratio of tetrahedral-to-trigonal carbon atom hybridization. A critical thickness for the effective protection of the magnetic medium by the a -C film is estimated from MD results. The results of this study elucidate the nanomechanical and nanotribological properties of ultrathin a -C films used as protective overcoats in extremely-high-density magnetic recording.

Nickel-titanium (Ni-Ti) alloys are normally associated with applications that exploit their shape memory characteristics. When properly formulated and processed, however, Ni-Ti is dimensionally stable and offers a unique blend of attributes suitable for tribological applications. This paper demonstrates that Ni-Ti alloys are promising candidate structural materials for oil-lubricated rolling and sliding contact applications such as bearings and gears. Ni-Ti alloys offer a broad combination of physical properties that make it unique among bearing materials. Ni-Ti alloys are hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, non-galling and non-magnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Spiral orbit tribometer (SOT) tests were conducted using 60NiTi balls loaded between rotating 440C disks, lubricated with synthetic oil and tested in a vacuum. Excellent tribological performance (life and friction) was observed and lubricant degradation normally associated with titanium alloys was absent. It is anticipated that the Ni-Ti family of alloys may form the basis of an entirely new class of bearing and component materials.

This study explored the effect of oil dilution with biodiesel and ultra low sulfur diesel fuel on acidity and corrosion in two lubricants with API service ratings of CJ-4 and CI-4+. The oils were diluted to levels of 0%, 5% and 10% with ultra low sulfur diesel fuel (ULSD), 20% biodiesel (B-20) and 100% biodiesel (B-100). For each case, the mixture of fuel and oil was subjected to oxidation tests using a procedure similar to ASTM D6594. The oxidation resistance of the CJ-4 and CI-4+ lubricants was similar in each case. The advanced formulation of the CJ-4 lubricant gave comparable overall performance to the CI-4+ lubricant, despite reduced levels of metallic additive compounds. The highest levels of lubricant degradation occurred when the lubricants were diluted with B-100. A substantial increase in acidity was observed when the oils were diluted with B-100. Moderate levels of copper and lead corrosion were observed in the tests with no fuel dilution, and dilution with ULSD. An order magnitude increase in corrosive wear was seen in the tests with B-100. Lower corrosion occurred with the CJ-4 lubricant.

The degree of acidification is considered a crucial property of lubricating oils for some applications, e.g. gas engines, as corrosive wear of machine components may be caused by acidic contaminations. For this reason, a sensor concept using the effect of material loss of a thin metal film due to corrosion is proposed. The corrosion of these films prepared from lead has been monitored electrically. In laboratory tests, the sensors were immersed in a series of oils characterized by different types and amounts of acidic components. The usefulness of the proposed sensor concept is also illustrated by corrosion tests with used oil samples taken from engines. The experiments clearly showed a correlation of corrosion rate with acidification expressed as TAN.

Fretting corrosion is one of the important factors which limits the lifetime of electric contacts. In order to avoid fretting corrosion coatings of different precious metals are used. The wear resistance of the coating determines the lifetime of electrical contacts. The long term characteristics of gold coated electrical contacts with different additives and contact shapes are investigated and the results are analyzed. It is found out that the wear resistance of contact coating can be largely influenced by the amount of the additive in gold and by the design of the contact shape. Only the combination of an optimized contact shape with suitable coating materials leads to a long term stability of electric contacts.

More and more attention has been paid to alternative fuel in internal combustion engine. One of alternative fuels is to convert straw biomass to biomass fuel. Various methods and apparatuses used for converting straw biomass to bio-fuel were invented and developed. However, alternative fuel from biomass can not be used well in internal combustion engine. The reason is complicated and relative with the separation technology of bio-fuel and corrosion, wear, lubrication and combustion chemical reaction between bio-fuel and the surface of combustion room. It is necessary to study the tribological properties of bio-fuel in order to instead the current gasoline or diesel oil in internal combustion engine in the future. In the present study, the straw based bio-oil obtained by liquidizing process was chosen to evaluate its lubrication by MQ-800 fourball tribometer, in which extreme pressure and friction coefficient and wear resistance were measured respectively. The experimental results showed that the extreme pressure of the bio-fuel was up to 392 N, and the extreme pressure of diesel oil was 333 N. The frictional coefficient of bio-fuel varies between 0.08 and 0.11. The wear scar diameter increased with load slowly in 30min. SEM images indicate that lots of thin and dense belt-like ploughs were presented on the rubbed ball surface. The chemical compositions of the worn zone on the ball surface were analyzed by XPS, the thermal property and variation of chemical compositions of bio-fuel before and after friction and wear tests were studied by TGA and GC-MS, respectively. It was shown that the rubbing surface film was composed of FeS, FeSO 4 and organic compounds with C-C, −COH and −COOH groups.

Magnesium, a light-weight metal, has been used as a construction material since the early days of the 20 th century. Excellent availability and low specific weight are the main benefits for applications in the aerospace and automotive fields. Because of a vast increase of Magnesium machining applications in the mobile equipment manufacturing industry over the last 10 years, there is an increasing demand for specially adapted cutting fluid systems for the machining of Magnesium parts. This paper will provide an overview on the latest research activities in Germany to develop new cutting fluid systems for a safe and economically efficient use of metal working fluids in mechanical processing of Magnesium alloys. Laboratory results and field applications with new innovative water-miscible cutting fluids are demonstrating that it is possible to control the huge problems of the past, such as hydrogen formation, emulsion split and corrosion. Based on experiences in the biggest european magnesium Machining project, the “Al/Mg Hybrid Crank Case” (Fig. 1), problems and solutions specific for large scale machining of Magnesium alloys with water-mixed cutting fluids are shown.

Recently, a number of sensor principles to measure physical and chemical properties of lubricating oils were investigated. The crucial property of lubricating oils for some applications is the degree of acidification as there is a correlation to corrosive wear of engine components. Corrosiveness is of particular importance for biogas engines due to the fact that bio-fuels are forming more aggressive components during the combustion process as in comparison with conventional fuels. Recent research showed that the corrosiveness of oil cannot be described sufficiently by conventional oil parameters such as total acid number and neutralization number. We propose a sensor concept using the effect of material loss of a thin metal film due to corrosion. The signal of the sensor being immersed in used gas engine oils with corrosive compounds showed good correlation with selected oil properties determined in the laboratory.

Two electrochemical techniques were used to investigate the corrosion of DLC coated magnetic hard disks: (1) potentiodynamic and potentiostatic anodic polarization and (2) electrochemical impedance spectroscopy. The objective was to determine the ability of DC polarization and AC polarization to detect the presence of porosity in the DLC. The results indicate that anodic polarization at high potentials (≈ +1.0V vs SCE) to cause pitting corrosion of the metal layers underneath the DLC might provide a rapid and quantitative estimate of the amount of porosity in the DLC. Measurement of the low frequency electrochemical impedance at intermediate potentials (≈ +0.5V vs SCE) appears to indicate the presence of porosity but further work is required to establish a quantitative relationship between the amount of porosity and the value of the low frequency impedance.

Nitrogenated carbon (CN x ) films were synthesized by using pulsed dc magnetron sputtering. When grown with substrate tilt of 45° and rotation speed of 20–25 rpm, the root-mean-square surface roughness is ∼0.3 nm when sampled over 20×20 μm 2 areas, increasing to ∼0.4 nm when sampled over ∼0.05×3 cm 2 using x-ray reflectivity measurements. X-ray reflectivity measurements showed that the mass density of these CN x films is ∼2.0 gm/cc, independent of film thickness from ∼1 to 10 nm, consistent with ion beam analysis. CN x films deposited with substrate tilt of 45° and rotation speed of 20–25 rpm have about 1/3 fewer corrosion spots per unit area than those without. Reducing CN x thickness from 3 to 1 nm results in marked increase in corrosion currents.

An oil-soluble additive organic molybdenum complex (MC) was synthesized. The antioxidation properties of a formulation including polyalphaolefin synthetic lubricant (PAO), the complex of p, p.-dioctyldiphenylamine (DODPA) and MC, were evaluated by a differential scanning calorimetry (DSC) test and oxidation-corrosion (OC) tests. DSC test measures the incipient oxidation temperature (IOT) and oxidation induction time (OIT) of the lubricant at high temperature and the oxidation stability of the oil including viscosity and total acid number increase are measured by OC test. In the first test, the IOT and OIT of the PAO containing DODPA were improved respectively after combining with MC. In the oxidation-corrosion test, in comparison to the base fluid, the additive hardly exhibited antioxidation properties, but the combination of MC with DODPA showed a reduction in viscosity Increase of about 32.4%. The Total acid number increase was 25.4% less than those of the lubricants containing DODPA. In the modified Penn State Micro-Oxidation Test (MPMOT), the combination of DODPA with MC can exhibits good deposit inhibition in PAO. These results indicate that MC shows good oxidative synergisms with DODPA antioxidant. In addition, the changes occurring to DODPA in the oxidation of the PAO with and without MC were followed by gas chromatography mass spectrometer (GC/MS) measurements. Finally, the antioxidation synergism of the formulation of MC with DODPA was proposed.

In this paper, the corrosion properties of vegetable oils as base oil for industrial lubricants are evaluated by the copper strip corrosion test (ASTM D130) and rust prevention test (ASTM D665). An analysis of possible organic reaction mechanisms leading to corrosion of metals in the absence and presence of oxygen and moisture is presented, when vegetable oils are used as base oils. Corrosion properties of vegetable oil fatty acids, evolved as degradation products, are analyzed using quantum chemical calculations. The popular quantum chemical software Spartan 04, Wavefunction Inc., USA was used for the studies employing the semi empirical PM3 method. The calculations were performed in line with similar reported studies used to analyze the corrosion inhibition properties of many nitrogen and sulfur containing anti corrosion additives. The corrosion inhibition properties of ZDDP (zinc dialkyldithiophosphate) were compared to other additives using PM3 semi empirical calculations. Moisture content in vegetable oils is found to be the leading cause of corrosion in vegetable oil based lubricants. Control of moisture content and use of additives like ZDDP can be effective in controlling corrosion.

One of the fields of tribology is to predict wear to ensure reliability for mechanisms that mechanical engineers design. Since the middle of the XX th century, lots of wear investigations have been done. Nowadays we can find a huge list of wear mechanisms (abrasion, adhesion, corrosion, etc) and more than one hundred wear laws, involving more than one hundred independent parameters. For Meng & al. [1], “the available equations are so confusing that few designers can use any of them to predict product life with confidence”. For Godet [2] “adhesion, abrasion, fatigue etc. are not wear but [only] particle detachment mechanisms”. And finally, from [1], we shall “develop full descriptions of the evolution of macroscopic events on sliding surfaces. This must include a description of the formation and movement of fragmented particles in the interface region”. The medium at the interface, constituted by detached particles from the materials or even by the oil in the case of lubrication, is then called “third body”.