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The mechanisms of boundary lubrication were investigated by comparing the capability of selected oil blends to protect 52100 steel, silicon nitride, and partially stabilized zirconia from wear. A four-ball wear tester was used and the test parameters were varied to find the optimum conditions for each material/lubricant combination. Additives were considered effective when both the wear rate in the...
There is a need to better understand the behavior of perfluoropolyalkylether (PFPAE) fluids under boundary lubrication so that their interaction with metal surfaces may be modified by additives or by other means. In this study, the effects of temperature, substrate steel type, an antiwear additive, and atmospheric humidity on the protective surface film formation in a linear PFPAE fluid were studied...
Boundary-lubricated spherical roller thrust bearings have been experimentally studied. Quantitative depth profile analysis of boundary layers by glow discharge optical emission spectroscopy (GD-OES), three-dimensional surface topography measurements and friction measurements were performed. The results show that both the boundary layer and the wear of the contacting surfaces were affected in a statistically...
For the combinations of four kinds of roll metal pins finished by two methods and an Al-killed steel disk rolled, friction and wear tests were carried out under the boundary lubricated condition at a sliding speed of 1.88 m/s and under a constant load of 3.7 N and a constant sliding distance of 7000 m. A topographical analysis has also been performed on the micro-asperities of the wear surfaces to...
The possible partial replacement of zinc dialkyldithiophosphate (ZDDP) by a multifunctional additive (borate-sulphonate micellar compound) was studied. X-ray absorption spectroscopy at the phosphorus, sulphur and boron edges was used to determine the chemistry of the tribochemical films, both at the surface and in the bulk. XANES data suggest an interaction between ZDDP and the borate additive. The...
The initial sliding wear of boundary lubricated piston rings used in a hydraulic motor is studied in terms of the changes in mass, form and surface roughness. The piston ring in a hydraulic motor makes an important contribution to high volumetric efficiency by properly sealing the cylinder bore and piston. The results show that the wear on the piston ring in this particular test rig takes place at...
Starting from a rigid-plastic model of asperity sliding, a finite element model of elastoplastic asperity sliding is developed. Its results are encapsulated in closed form correlations with non-dimensional groups selected on the basis of the rigid-plastic solution. This permits friction and wear coefficients to be predicted for some simple sliding contacts using techniques of surface characterisation...
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...
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...
Improvement of fuel economy and component durability as well as reduction of dependence on some harmful components of lubricants are the key concerns for automotive industries. In recent years, efforts have been made to use surface engineered surfaces in automotive components to produce environmentally friendly vehicles as well as to increase fuel economy. Since commercially available lubricants are...
This paper is concerned with an experimental investigation of the boundary lubrication properties of magnetorheological (MR) fluids under point sliding contacts between polytetrafluoroethylene (PTFE) and stainless steel tribopairs. The tribological properties of OM, OS, OX, HS, HSI and HQ grades of carbonyl iron based MR fluids were tested using a ball-on-three plates tribometer to ascertain the optimal...
Diamond-like carbon (DLC) coatings offer excellent mechanical and tribological properties. They provide ultra-low friction and superior wear resistance. In recent years, the research of DLC coating focuses on the application of these coating in mechanical components which work under boundary lubricated conditions. Since conventional lubricants and lubricant additives were formulated for metal surfaces,...
A modelling framework has recently been developed which considers tribochemistry in deterministic contact mechanics simulations in boundary lubrication. One of the capabilities of the model is predicting the evolution of surface roughness with respect to the effect of tribochemistry. The surface roughness affects the behaviour of tribologically loaded contacts and is therefore of great importance...
In this study, the lubricated friction and wear associated with diamond-like coatings (DLCs) of amorphous hydrogenated carbon (a-C:H) and hydrogen-free tetrahedral amorphous carbon (ta-C) were comparatively analyzed. The effects of load and sliding distance on the wear and friction behaviors of the coatings were studied under a boundary-lubrication condition using a poly-alpha-olefin base oil. The...
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