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The electrical contact resistance is measured between the tool and workpiece during plane strain compression of aluminium strip coated with a non-conductive oxide film produced by anodising. Results are correlated with the observed oxide topography after the test. The purpose is to investigate the mechanism of the development of close metal-to-metal contact, the associated material transfer and their...
A molecular dynamics simulation is used to investigate the effect of surface roughness on the nano-rheology of ultra-thin films confined between two solid walls. The results show that friction is sensitive to the confining surface morphology and the fluid molecules near the two confining surfaces are in a layering solid-like structure. At a high shear rate, the interfacial layers of the film stick...
The tribological characteristics of a magnesium alloy, AZ91D, were investigated in a sliding lubricating system using various N-containing compounds as lubricating additives on a Timken type tester against a bearing steel (AISI52100) ring. Results indicated that a significant improvement in the tribological performance exists using N-containing compounds as additives. The characteristics of anti-wear,...
Effects and mechanisms in minimal quantity lubrication are investigated by use of an intermittent turning process. Especially a difference between minimal quantity lubrication (MQL) and MQL with water is inspected in detail to elucidate boundary film behaviour on the rake face. In order to obtain a good cutting performance by MQL it is considered that two things are needed: (1) an appropriate lubricant,...
The aim of the present investigation was to obtain some further understanding of the mechanism responsible for low-friction behaviour of W-containing DLC coatings (W-DLC) when lubricated with EP additivated oil. Boundary lubricated wear and friction tests were performed under reciprocating sliding motion using a high frequency test rig and a contact pressure of 1.5GPa. Additionally, some of the tests...
Hydrogen embrittlement is often a catastrophic phenomenon of machine elements failure under cyclic stresses. This hydrogen is generated as a result of tribo-chemical and mechanical actions on the working surfaces. This hydrogen can have three different zones or stages of behaviour under tribo-mechanical actions. Firstly, it can strongly adsorb on the mating surfaces at a shallow subsurface zone and...
A new aluminum bronze material with aluminum content over the solubility limit and several trace elements, Cu–14Al–X alloy (X is trace elements), has been developed for drawing dies. The mechanical properties such as hardness, tensile strength and impact toughness were evaluated experimentally. The friction and wear behavior of the material was investigated under boundary lubrication conditions. The...
The initial stage of boundary film formation from overbased calcium sulfonate at steel–DLC (diamond like carbon) contact was studied. A running-in process was clearly observed by the combination of fresh DLC with fresh steel or fresh DLC with rubbed steel. On the other hand, rubbed DLC does not possess the running-in process. Surface analysis by TOF-SIMS was applied to investigate the formation process...
This study reports on the effects of surface modification by laser texturing on tribological performances of nitriding steel for high-performance engine applications. In particular, a comparison of tribological properties on untextured and textured 30NiCrMo12 nitriding steel was made among hydrodynamic, mixed and boundary lubrication regimes.Ordered arrays of circular dimples were created on nitriding...
This paper presents experimental results of wear process under dry and boundary lubricated metallic (AISI 1034/AISI 52100) contacting bodies with different surfaces morphologies subjected to a wide range of kinematic fretting conditions. Analysis of damage mode observed under such fretting conditions is elucidated in context of surfaces morphologies therefore associated with surface manufacturing...
The friction coefficient was measured under boundary lubrication with a ball-on-flat contact configuration in unidirectional sliding. The ball was smooth and hardened 52100 steel. Discs were made from case-carburized and hardened 4620, annealed 1080, and 1018 steels with directionally ground surfaces. A synthetic lubricant of stock polyalphaolefin was used for testing. During testing with each material,...
The role of di-tert-dodecyl disulfide as an additive in the decomposition process of hydrocarbon oil on the nascent surface of bearing steel 52100 was investigated by a ball-on-disk friction tester in a vacuum chamber with a quadrupole mass spectrometer (Q-MS). After the formation of a nascent surface, hydrogen and gaseous hydrocarbons desorbed as tribochemical reaction products. The desorption rate...
A series of long-chain 1,3-dialkyl imidazolium ionic liquids (ILs) were synthesized and evaluated as lubricants for steel–steel contacts both at room temperature and 150°C. Relationship between the alkyl chain length and the tribological properties of the ILs was investigated in detail. The results indicated that the ILs bearing long alkyl side chains have excellent friction-reducing and anti-wear...
AISI 52100 steel was treated by means of plasma nitriding and exhibited remarkable friction stabilization when sliding against AISI 52100 steel under lubrication conditions with alkyl naphthalene, compared with heat quenched and untreated samples. In the presence of lubricant additives, ZnDDP and PN (amine salt of alkoxyl phosphate), the system displayed excellent friction steady-state and low friction...
The effect of contact load and volume of lubricant in the time to tribofilm breakdown and extent of wear was examined in fully formulated oil with zinc dialkyl dithiophosphate as the main anti-wear additive. The mechanism of tribofilm formation and breakdown was followed carefully by monitoring the friction coefficient over the duration of the test. Tribological tests conducted with limited lubricant...
The lubrication of Micro-Electro-Mechanical Systems (MEMS) has been a major obstacle to the micromachine industry, limiting the designs commercially available and actuating/sensing mechanisms in micro actuators/sensors to mostly non-contacting ones. MEMS are traditionally made of silicon (Si), which has very poor tribological properties. Lubrication techniques for MEMS usually involve highly expensive...
Ashless antiwear additives have begun to find applications in automotive and heavy industry applications as sludge formation is reduced leading to improved efficiency. In this study, six different ashless antiwear agents, including an ashless neutral dialkyl dithiophosphate (DDP-1), an acidic dialkyl dithiophosphate (DDP-2), an alkylated triphenyl phosphorothionate (A-TPPT), a butylated triphenyl...
A nanocomposite polymer coating of ultra-high molecular weight polyethylene (UHMWPE) reinforced with 0.1wt% of single-walled carbon nanotubes (SWCNTs) is developed and coated onto steel substrates for a possible application as a boundary lubricant in bearings and gears. Since temperature is one of the predominant factors in determining the tribological performance of polymer coatings, friction and...
In the present study, five kinds of liquid lubricants, including MACs, IL, Zdol, PAO and silicon oil, were homogeneously spun on DLC coatings and consequently the DLC-based solid–liquid lubricating dual-layer coatings were successfully fabricated. The tribological behaviors of the DLC/steel combinations and steel/steel combinations lubricated with above five liquid lubricants were comparatively investigated...
During the running-in of surfaces a change in roughness takes place. The presented model predicts this change for concentrated contacts using an elasto-plastic contact model based on a semi-analytical-method recently developed. Combining this method with a local coefficient of friction, which is determined using a mechanical threshold on the protective nature of the lubricant, and a strain related...
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