M. Abdul Samad

Ultrathin Si/C graded layer to improve tribological properties of Co magnetic films

An ultrathin Si layer (≤1 nm) deposited on Co magnetic films was bombarded with energetic C+ ions to form a Co/Si/C mixed layer. This layer improved the tribological properties of the Co film as compared with those of a commercial hard disk media with 3.0 nm carbon overcoat and 1.4 nm of lubricant. Formation of a network of C-C and Si-C bonds at the outermost layer and the bulk of the Si/C film as well as formation of chemical bonds between the Co surface and the mixed layer was found as the main factors to improve the tribological properties.

Effect of carbon embedding on the tribological properties of magnetic media surface with and without a perfluoropolyether (PFPE) layer

Carbon embedding (≤1 nm) in the top surface of cobalt (~100 nm) sputtered on a silicon surface is used as a surface modification technique to evaluate the tribological properties with or without an ultra-thin layer of perfluoropolyether (PFPE) lubricant. The carbon embedding is achieved using the filtered cathodic vacuum arc technique at an ion energy of 90 eV. Transport of ions in matter simulations, time-of-flight secondary ion spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy (XPS) are used to study the carbon embedding profiles and surface chemical composition. The XPS results show that carbon embedding using the ion energy of 90 eV results in the formation of about 58 ± 6% of tetrahedral (sp3) carbon hybridization. Furthermore, the XPS results also show that the carbon embedding is effective in improving the anti-oxidation resistance of cobalt. Ball-on-disk tribological tests are conducted at a contact pressure of 0.26 GPa on the modified cobalt surface with or without the PFPE layer. It is observed that the average coefficient of friction is reduced considerably from a value of approximately 0.7 to 0.42 after the surface modification. The coefficient of friction is further reduced to ~0.26 after the deposition of an ultra-thin layer of PFPE over the modified surface, which is lower than a friction coefficient of 0.4 from commercial media. The modified cobalt surface also shows much better wear life than the present day commercial media.

Effect of Air-Plasma Pre-treatment of Si Substrate on Adhesion Strength and Tribological Properties of a UHMWPE Film

Ultra High Molecular Weight Polyethylene (UHMWPE) film is dip coated onto piranha and air–plasma treated silicon substrates, to study the effect of surface pre-treatment on the adhesion strength and the tribological properties of the film. After the pre-treatment, water contact angle measurements were conducted and the surface free energy of the Si substrate was calculated. It is observed that the air–plasma pre-treatment reduced the water contact angle (4.3°) considerably when compared to that of the piranha pre-treatment (21.3°), which resulted in an increase of the surface free energy of the Si substrate. Scratch tests were conducted for studying the adhesion property of UHMWPE films coated onto Si substrate. It was found that the plasma pre-treatment enhanced adhesion between the UHMWPE film and the Si substrate by more than two times when compared to the piranha pre-treatment. Wear tests were conducted to study the effects of pre-treatments on the tribological properties of the UHMWPE film. UHMWPE film coated onto plasma pre-treated Si showed a wear life of about 50 000 cycles (25 times higher) as compared to that of 2000 cycles when it was coated onto piranha pre-treated Si, tested at a normal load of 1 N and a rotational speed of 200 rpm.

Thermal treatment effect on structural and mechanical properties of Cr–C coatings

ABSTRACT In the present study, the effect of thermal treatment on the mechanical and structural properties of chromium carbide coatings with different thicknesses is evaluated. The coatings were deposited by cathodic magnetron sputtering on XC100 steel substrates. Samples were annealed in vacuum, at different temperatures ranging from 700 to 1000°C for 1 h, resulting in the formation of chromium carbides. X-ray diffraction (XRD), microanalysis X/energy-dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy analysis were used to characterise the samples. Mechanical properties were evaluated by nano-indentation tests and the residual stress was calculated with the Stoney formula. The XRD analysis suggests the formation of the Cr7C3, Cr23C6 carbides at 900°C. For thin films, they transformed totally to ternary (Cr, Fe)7C3 carbides and their partial transformation has been observed in the case of thick films at 1000°C, without the formation of Cr3C2. The EDS and XPS showed the diffusion mechanism between the chromium film and the steel substrate for the Cr, Fe, C, O elements during the annealing treatment. The increase of chromium film thickness from 0.5 to 2.64 µm, contributed to the significant enhancement of mechanical properties such as hardness (H) (from 12 to 26.3 GPa) and Youngs Modulus (E) (from 250 to 330 GPa), respectively.

Introducing CAD/CAM and CNC machining by using a feature based methodology in a manufacturing lab course, a conceptual frame work

In a continuous effort to develop and incorporate innovative teaching styles in the Mechanical Engineering curriculum at King Fahd University of Petroleum and Minerals (KFUPM), a new lab course titled Advanced Manufacturing Lab (ME-407) has been introduced, wherein the senior students are exposed to Computer Aided Drafting (CAD) and computer aided manufacturing (CAM). The main objective of this course is to inculcate the knowledge in the area of CAM software, its application in computerized numerical controlled (CNC) machining, metrological study and data generation for statistical analysis. For doing so, a comprehensive project is being developed which integrates all the above elements. This paper outlines a proposed strategy to accomplish these targets and a set of carefully selected activities to follow when this new course starts.