Diamond-like carbon (DLC) coating technology has been receiving increasing attention in recent years for its application to automotive sliding parts. As it is critical to evaluate the adhesion strength between a film and a substrate for assessment of the reliability of DLC films, a practical method to assess film damage under repeated sliding motions is needed. This research clarified the conditions under which damage is generated on Si-containing DLC films by analyzing damage modes such as wear, spalling, and cracking of the films under an automatic transmission fluid (ATF) lubrication condition and repeated sliding friction. The research also confirmed the effectiveness of the evaluation method. The test results indicated that the Si-containing DLC film has the highest reliability compared to the other types of films tested using the same test method.

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This paper presents an experimental study of roughness characteristics of electroless Ni-P coatings and optimization of coating process parameters based on L₂₇ Taguchi orthogonal design. Experiments are carried out by utilizing the combination of three process parameters, viz., bath temperature, concentration of nickel source solution and concentration of reducing agent. It is observed that concentration of nickel source solution has got the most significant influence in controlling roughness characteristics of electroless Ni-P coating. The optimum combination of process parameters for minimum roughness is obtained from the analysis. The surface morphology and composition of coatings are also studied with the help of scanning electron microscopy, energy dispersed X-ray analysis and X-ray diffraction analysis.

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Ensuring effective lubrication between sliding surfaces is one of the challenges in the field of tribology. In addition to the conventional parameters like speed, load, contact geometry and material parameters, the surface texture also influences the coefficient of friction. In the present investigation, the effect of surface texture on coefficient of friction under boundary lubricated condition was studied by sliding Al-4Mg alloy pins against EN8 steel discs of various surface textures using pin-on-disc machine. Both isotropic and directional textures were generated on the surfaces of the discs. Scanning Electron Microscopy and optical profilometer studies were carried out on the contact surfaces of both the pins and discs before and after the experiments. The result showed that the coefficient of friction varied considerably with surface textures. In addition, maximum value coefficient of friction was observed when pins slid perpendicular to the unidirectional texture and minimum when pins slid on random texture. Backscattered scanning electron micrographs revealed the transfer of iron from the disc to the pins and it was highest when pins slid perpendicular to the unidirectional texture and least for the random texture. However, no transfer layer of Al-Mg alloy was observed on the steel disc.

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A three dimensional non-contact surface profilometer system which can measure a wide area (order of square milli-meters) with high resolution (sub micro meter) has been completed. This system can measure the surface topography in the atmosphere by means of a confocal wavelength displacement sensor. We examined the optimum measurement conditions and applied them to the evaluation of erosion properties of particle reinforced metal composites. As a result, a scanning speed of 1mm/s and sampling intervals of 0.5-15μm were found to the optimum conditions. In addition, we evaluated the differences of properties in composite materials with different volume fractions using this system. We conclude that our technique is useful in the evaluation of erosion properties of composite materials.

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Surface topography influences friction and transfer layer formation during sliding. In the present investigation, various kinds of surface topography were produced on steel plates. Pins made of metals (pure Al, Cu and Pb) and alloys (Al-4Mg and Al-8Mg) were then slid against prepared steel plates using inclined pin-on-plate sliding tester to understand the role of surface topography of harder surface and load on friction and transfer layer formation under both dry and lubricated conditions. It was observed that the transfer layer formation and coefficient of friction along with its two components, namely adhesion and plowing, are strongly dependent on surface topography and independent of surface roughness (R_a). The plowing component of friction was highest for the surface that promotes plane strain conditions and lowest for the surface that promotes plane stress conditions near the surface.

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Controllable yield strength of Magnetorheological (MR) suspensions makes them suitable brake material. MR-fluid and MR-grease are two commonly explored MR suspensions, and comparison between their performances is useful to decide their suitability in MR brake applications. The current paper presents such comparison. MR fluid and MR grease have been specially formulated. Ninety percent (weight percent) of Xanthan gum coated electrolytic iron powder has been used for synthesis of both MR suspensions. Two identical brake assemblies, one for MR-fluid and other for MR-grease have been developed. Experiments have been performed in the same operating conditions of speed and magnetic field for MR fluid brake and MR grease brake, and their performances of brake power output and amplification factor has been reported.

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