In this study, nanostructured diamond (NSD) films were grown, by microwave plasma assisted chemical vapor deposition (MP-CVD) technology, on WC-Co drills for performance enhancement in dry drilling of A390 alloys. Surface cobalt was removed by a well-controlled precision etching process. H 2 /CH 4 gas mixture with a small amount of N 2 was applied to produce NSD films. Moreover, slight hone was applied to the cutting edges prior to the NSD deposition to relieve residual stresses generated by thermal mismatch in depositions. The results show feasibility of dry drilling of A390 alloys by NSD coated drills, substantially outperforming carbide drills.

Fully formulated metalworking fluids have been thoroughly described in literature, but the influence of individual additives on tribological performance of such compositions is still not fully clear. In this study we want to establish the mechanism of how different additives affect tribological properties of the system, and to select the best compounds and concentrations for this purpose. The influence of various individual additives on friction behaviour, anti-wear and anti-corrosion properties of metal working fluids was examined. Additionally, chemical characterisation of the surfaces before and after tribological tests was done. The results show that additives can enhance one property while adversely affecting another. The best results were obtained for triethylamine and 1, 4-buthylene glycol, however mixing both additives gives opposite behaviour.

Surface micro dents may act as lubricant reservoirs to reduce friction and wear in sliding and rolling contact applications. Surface patterning has become a valuable technique for fabricating micro dents. Alternative methods such as micromachining present obvious limitations in comparison with laser shock peening (LSP). In this paper, the use of LSP along with an automatic X-Y table proves to be an attractive and reliable method for producing micro dent arrays with enhanced surface integrity and free of cracks. Surface topography, residual stress, and microhardness of the fabricated micro dent arrays on polished Ti-6Al-4V have been characterized. It was found that a 10% density of micro dent array reduces coefficient of friction compared with a smooth surface. However, a higher dent density not necessarily reduces coefficient of friction.

Understanding the tribological aspects of machining processes are essential for increasing the dimensional accuracy and surface integrity of products, as well as gaining a better control of tool wear, chip handling and power consumption. The objective of this investigation is to develop numerical models that accurately predict the chip formation and stress profiles in the work-piece during orthogonal metal cutting using the explicit finite-element method (FEM). In our simulations, a damage material model was utilized to capture the work-piece chip separation behavior and the simultaneous breakage of the chip into multiple fragments. In the simulation, the rigid steel cutter of different rake angles was moved at different velocities against a stationary aluminum work-piece at constant friction for a cutting depth of 1 mm. Overall, the results indicate that the explicit FEM is a powerful tool for simulating metal cutting and discontinuous chip formation. The rake angle had a significant effect on the formation of chip during metal cutting. The formation of discontinuous chip along the contact interface was hypothesized to be due to the internal crack initiation and propagation in front of the tool and above the cutting edge, rather than from the free surface.

In the present investigation, sliding experiments were conducted using pins made of pure Al, Al-4Mg alloy, Al-8Mg alloy, Mg-8Al alloy and pure Mg against steel plates of various surface textures using a pin-on-plate apparatus under both dry and lubricated conditions. The primary focus of the study was to investigate the influence of alloying elements on the coefficient of friction and transfer later formation in Al-Mg systems. The morphologies of the worn surfaces of the pins and the formation of transfer layer on the counter surfaces were observed using a scanning electron microscope. It was observed for a given surface texture that the alloying element addition decreased the average coefficient of fiction to lower values under both dry and lubricated conditions. For a given material pair, the coefficient of friction and formation of transfer layer depend on the surface texture of the hard surfaces.

In this paper, chip formation process during mechanical cutting of rock is simulated by using an explicit finite element code, LS-DYNA. In the simulation, the work-piece material properties have been modeled using the damage constitute material model. This model simulates the separation of the chip from the work-piece and the simultaneous breakage of the chip into multiple fragments. In the simulation, a rigid steel tool was moved at various sliding velocities, namely 1, 4, 10, 50 and 100 mm/s against a stationary rock material. For a given sliding velocity, the simulations were carried out for various cutting depths, namely 1, 2, 3 and 4 mm. The variation of stresses and the amount of chip formation at different depths of cut and velocities have been investigated. Overall, the results indicate that the explicit FEM is a powerful tool for simulating rock cutting and chip formation. More specifically, the separation of chip from the work-piece at different depths of cut was distinctly shown using this numerical model.

In the present investigation, unidirectional grinding marks were attained on the steel plates. Experiments were then conducted using pins of Al-Mg alloy against the prepared steel plates using an inclined pin-on-plate sliding tester. The goal of the research is to understand the influence of grinding mark direction and inclination angle of hard material on the friction and transfer layer formation during sliding. The inclination angle of the plate was held at 0.2°, 0.6°, 1°, 1.4°, 1.8°, 2.2° and 2.6° in the tests. The pins were slid both perpendicular and parallel to the grinding marks direction. Experiments were conducted under both dry and lubricated conditions on each plate in ambient environment. Results showed that the coefficient of friction and formation of transfer layer depend on the grinding marks direction and inclination angle of the hard surfaces. For a given inclination angle, the coefficient of friction and transfer layer formation were found to be more for the pins slid perpendicular to the unidirectional grinding marks when compared to parallel to the unidirectional grinding marks under both dry and lubricated conditions. The stick-slip phenomenon was observed only under lubricated conditions at the highest tilt angle for the sliding perpendicular to the grinding marks direction. These variations could be attributed to the extent of plane strain conditions taking place at the asperity level during sliding.

This study investigates the chip clogging phenomenon which occurs in dry drilling of aluminum alloys and composites, and yet, is seemingly critical to the drill life. This issue must be resolved in order to facilitate dry drilling. A highspeed dry drilling test using common twist drills was conducted with the workpiece temperature pre-heated to a wide range, room to 265 °C. The drills after testing were then examined in terms of aluminum residue that strongly adheres with the flute surfaces. A possible transition temperature range that may result in severe aluminum build-up and chip clogging was identified under the tested condition.

The tribological behavior of AA5083 aluminum sheet sliding against tool steel impacts the quality of components manufactured with the Quick Plastic Forming (QPF) process. The effect of boron nitride lubricant thickness on the tribological performance of different coated steel/AA5083 pairs utilizing a recently developed reciprocating flat-on-flat tribological test technique was investigated. In most cases of coated and uncoated steel, the time-to-contact increased by a factor of ten when the BN thickness was increased from 8.4 μm to 14.5 μm. The tribological tests with a low sliding speed method (0.1 Hz) confirmed the previous observations conducted at 0.5 Hz in which nitrocarburizing of the tool surface decreased adhesion of aluminum to the steel during sliding contact.

CMP process yield depends on effectiveness of a post-CMP cleaning, which should reduce roughness of the polished wafer and leave it defect-free, consistently removing particles, organic residues, and ionic contamination. This paper presents an overview of wafer cleaning attributes, challenges and opportunities. The cleaning effectiveness depends on the stability of brush PVA (Poly Vinyl Alcohol) properties, magnitude of brush-wafer frictional force, and the adhesion forces between the particle and wafer, and the particle and brush.

Hot forming of aluminum sheet is highly influenced by the tribological behavior of the interacting surfaces of sliding pairs. Here we describe a new technique to investigate tribo-pair candidates for Quick Plastic Forming (QPF) and warm forming processes. This technique represents a bench type simulation of the real forming process where the sheet and tool interact by sliding against each other in a single motion (slide/stroke).

The tribology of hot forming processes is highly critical for the quality of formed aluminum panels and the cost-effectiveness of hot forming. In this report a flat-on-flat experimental technique for tribological evaluation of a single stroke was used to investigate the effect of sliding speed on the operative friction coefficient (FC) and tribological failure of the tribo-pairs used in Quick Plastic Forming (QPF) and warm forming processes.

Tribo-oxidation of metals plays important roles in electro-chemical-mechanical planarization (ECMP). Using an electrochemical-tribological technique, we conducted investigation of tantalum tribo-oxidation during ECMP. Adding an electrochemical system to a tribometer, we were able to monitor surface changes through friction. We were able to generate tantalum oxides with assistance of friction. It was found that meta-stable suboxides of tantalum formed. The mechanisms of tribo-oxidation are experimentally studied and discussed here.

CMP (chemical mechanical polishing) is a vital IC (integrated circuit) manufacturing process. CMP is performed by rubbing the IC surface with a roughened polyurethane polishing pad in the presence of a chemically active, abrasive containing slurry. Friction is a natural consequence of CMP, and this friction can damage next generation, mechanically weak, porous dielectric materials on the IC surface. Earlier research has been done to characterize this friction, but the data is confounded with hydrodynamic effects. More recent experiments have measured the coefficient of friction with varying slurry characteristics but at low speeds and constant normal load which could decouple hydrodynamic effects. This new research measures the coefficient of friction with varying low speeds and varying loads. The coefficient of friction had a very small, statistically significant decrease with increasing normal load. This effect was attributed to elastic Hertzian pad asperity deflection with friction force being proportional to the asperity contact area. At lower normal loads, there was not statistically significant change in the coefficient as a function of speed. At the highest normal load, there was a very small increase in the coefficient of friction as the speed increased. It is proposed that counter-intuitive trend was a result of the following mechanism. Time dependent surface hydration film reduces the coefficient of friction. This surface film is damaged by rubbing, and the lower speed permitted more time for the film to regenerate.

The weighting material in drilling fluid has very important effect on casing wear. By using the DCWT-1000 tester, a new impact-sliding tester for casing wear, a series of tests in impact-sliding work condition have been performed to investigate the effects of different weighting material doped in drilling fluid. The OE and SEM analysis presents that the iron ore powder doped in the drilling fluid led to the change in the wear mechanism from abrasive wear and adhesion wear to severe plastic flow and fatigue wear. The adhesion wear increasingly become severe with increasing iron ore powder content. While the barite doped in the drilling mud was beneficial to decreasing the adhesion wear and plastic deformation of the casing. Moreover, it is found that mixed weighting material with iron ore powder and barite in certain ratio has better effect on decreasing casing wear.

A semi-empirical model based on the physics behind tool wear that can depict the tool wear locally is developed to predict crater profiles of multilayer coated carbides. Dissolution and abrasion relationships are recast into a point-wise or local version to predict directly based on the temperature and pressure profiles from FE simulation. The approach is reasonable to explain the crater profiles observed in multilayer coated carbides. However, the model deviates from the real profiles due to the κ-to-α phase transformation in the middle Al 2 O 3 layer, the change in the friction conditions as each layer is exposed, and the combined wear resistance of multi-layers of the cutting tool.

Cutting tool wear of polycrystalline cubic boron nitride (PcBN) tools was investigated in oblique turning experiments when machining compacted graphite iron at high cutting speeds, with the intention of elucidating the failure mechanisms of the cutting tools and presenting an analysis of the chip formation process. Dry finish turning experiments were conducted in a CNC lathe at cutting speeds in the range of 500–800m/min , at a feed rate of 0.05mm/rev and depth of cut of 0.2mm . Two different tool end-of-life criteria were used: a maximum flank wear scar size of 0.3mm (flank wear failure criterion) or loss of cutting edge due to rapid crater wear to a point where the cutting tool cannot machine with an acceptable surface finish (surface finish criterion). At high cutting speeds, the cutting tools failed prior to reaching the flank wear failure criterion due to rapid crater wear on the rake face of the cutting tools. Chip analysis, using SEM, revealed shear localized chips, with adiabatic shear bands produced in the primary and secondary shear zones.

The tribological behavior of AA5083 aluminum sheet sliding against tool steel impacts the quality of components manufactured with the elevated temperature metal forming processes such as Quick Plastic Forming (QPF), Superplastic Forming (SPF), or warm forming. This study focuses on the tribological performance and evaluation of alternative solid lubricants using a flat-on-flat tribo-tester to simulate sheet forming at high temperature applications. Improved lubricant formulations containing boron nitride with graphite additions were found to enhance lubricity while maintaining good adherence to the surface of the aluminum blank at a temperature of 450°C.

In the present investigation, basic studies were conducted using Inclined pin-on-plate sliding Tester to understand the role of surface texture of hard material against soft materials during sliding. Soft materials such as Al-Mg alloy, pure Al and pure Mg were used as pins and 080 M40 steel was used as plate in the tests. Two surface parameters of steel plates — roughness and texture — were varied in tests. It was observed that the transfer layer formation and the coefficient of friction which has two components, namely adhesion and plowing component, are controlled by the surface texture of harder material. For the case of Al-Mg alloy, stick-slip phenomenon was absent under both dry and lubricated conditions. However, for the case of Al, it was observed only under lubricated conditions while for the case of Mg, it was observed under both dry and lubricated conditions. Further, it was observed that the amplitude of stick-slip motion primarily depends on plowing component of friction. The plowing component of friction was highest for the surface that promotes plane strain conditions near the surface and was lowest for the surface that promotes plane stress conditions near the surface.

Friction plays an important role in metal forming processes. In the present investigation, various kinds of surface texture with varying roughness were produced on steel plates. Pins made of Al-8Mg alloy were then slid against the prepared steel plates using inclined pin-on-plate sliding tester to understand the role of surface texture of the harder surface and load on coefficient of friction and transfer layer formation under both dry and lubricated conditions. It was observed that both the coefficient of friction and transfer layer formation are highly dependent on the surface texture of harder counterface. Numerical analysis of simulated compression test, assigning different magnitude of coefficient of friction at different regions between the die and work piece, was carried out to understand the effect of friction on deformation and stress distribution. Results of simulation revealed that, owing to the difference in coefficient of friction, there is a difference in metal flow pattern. Both experimental and numerical results confirmed that the surface texture of the die surface and thus coefficient of friction directly affects the strain rate and flow pattern of the work-piece.