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Problem statement: There is an increasing demand for claddings which possess an optimized combination of different functional properties such as high hardness, high resistance to wear and oxidation. In this respect, hard TiAlN cladding has gained much attention. These claddings can be suitable replacements for the conventional ceramic coatings applied in many components of chemical plants and automotive industries to protect against high temperature oxidation and wear. Approach: In this study the possibility of the formation of intermetallic and nitride claddings on plain carbon steel surfaces by in situ melting of preplaced titanium and aluminum powder mixture under Tungsten Inert Gas (TIG) torch had been investigated. Results: Addition of 1.3 and 1.8 mg [mm.sup.-2] Ti and Al powder and melting at energy inputs between 540-675 J [mm.sup.-1] in nitrogen environment successfully created more than 1 mm thick clad layer consisting of a mixture of titanium-aluminum nitrides and aluminides. All resolidified melt layers produced dendrite microstructures; the dendrite concentration is more near the surface area compared to the deeper melt depth. A maximum surface hardness of around 900 Hv was developed in most of the tracks and this hardness corresponds to high concentration of dendrites within the modified layer. Oxidation at 600[degrees]C for 72 h, of the clad steel gave weight gains of 0.13 mg [mm.sup.-2], compared to 0.37 mg [mm.sup.-2] for the substrate. Conclusion: The results showed that clad steel gave better mechanical and oxidation properties compared to plain carbon steel substrate. Key words: Clad layer, nitride, hardness, oxidation, INTRODUCTION Surface treatments are critical to the engineering of modern machine components and tools, where the underlying material is chosen for its bulk properties (elastic modulus and hot hardness) while [...]

Copper-tungsten composite materials are developed for applications such as electrical contacts, resistance electrodes, and contact tips in welding guns as well as for components requiring higher wear resistance. In addition to the aspect of improved performance, it is scientifically interesting to assess the tribological properties, and therefore the objectives of the present work include, to determine the role of W additions in improving the fretting wear resistance of Cu for electrical applications, to determine the optimum concentration for W additions, and to identify the mechanisms responsible for fretting wear improvements. In addressing these issues, a planned set of fretting wear tests were conducted on powder metallurgically processed Cu-W composites (maximum W content of 20 wt %) against steel counterbody under varying load (up to 10 N) for 10,000 cycles. It has been observed that at lower loads of 2 N, the coefficient of friction (COF) recorded was ~0.9 for the Cu-20 wt % W/steel, whereas it was ~0.85 for a pure Cu/steel couple. Under similar operating conditions with the increase in load, the COF decreases to 0.5 at 10 N load, irrespective of the composition of the Cu-W composite. Furthermore, the incorporation of 5 wt % W has reduced the volumetric wear loss by 4-6 folds in comparison to unreinforced Cu. The addition of even higher percentage of W has led to increase its wear resistance by ~10 folds. Under the investigated conditions, the wear rate systematically decreases with the increase in load for all the tested Cu-W composites. Based on the topographical observation of worn surfaces, it is observed that wear mechanisms for the Cu and Cu-W composites are tribochemical wear, adhesive wear, and abrasive wear. The incorporation of harder W particles (5 wt % or more) help in abrading the steel ball and in forming a dense tribolayer of [Fe.sub.x][O.sub.y], which effectively reduces wear rate and hence, increases wear resistance of the Cu-W composite surface in reference to unreinforced Cu. [DOI: 10.1115/1.3204776] Keywords: Cu, W, repeated pressing and sintering, fretting, wear, tribolayers, powder metallurgy

The mechanism of enhanced adhesion between hydrogenated amorphous carbon films and tungsten preimplanted steel substrates was systematically investigated. The results showed that preimplantation created a graded WC interface that diminishes diffusion of the dissociated carbon atoms on the surface and the films deposited on tungsten implanted steel substrates show improved adhesion strength.

The impact response of potassium bromide single crystals with and orientation is analyzed in a series of planar impact experiments under continuous monitoring of the sample rear surface velocity. The samples whose initial temperature varied between 166 and 880 K are loaded with aluminum, copper or tungsten impactors.

Several studies are conducted to explain the preparation, as well as the different electromechanical and electro-optic properties of the tungsten bronze [([Ca.sub.0.28][Ba.sub.0.72]).sub.0.25][([Sr.sub.0.6][Ba.sub.0.4]).sub.0.75][Nb.sub.2][O.sub.6] single crystal.

Systematic studies for diamond thin films deposited on WC-Co substrates are conducted to determine the relation between substrate surface irregularities and also study the effect of particular size on diamond nucleation. The deposited films of WC-Co substrate with higher surface fractal dimension are preseeded by fine diamond suspension in advance exhibited high diamond-rich composition and adhesion strength.

A hyperthermal neutral beam (HNB) source as one of suitable methods to reduce plasma-induced damage problems is described. A molecular dynamics algorithm is employed to simulate the HNB generated by vertical collisions between energetic ions and a reflector composed of a tungsten plate.

The nucleation and growth of W atomic layer deposition (ALD) on hydroxylated [Al.sub.2][O.sub.3] ALD surfaces and [Al.sub.2][O.sub.3] ALD on fluorinated W ALD surfaces is analyzed by using in situ quartz crystal microbalance (QCM) and ex situ atomic force microscope (AFM) methods. The QCM examinations have shown that [Al.sub.2][O.sub.3] ALD has nucleated on the fluorinated W surface and has displayed 'substrate-enhanced growth'.

A cold isostatically pressed mixture of polytetrafluoroethylene (PTFE), aluminum (Al), and tungsten (W) powders are used to explore the variation of metallic particle size and sample porosity, which significantly alters the dynamic mechanical properties of high density granular composite materials. The results from the numerical modeling of shock loading for granular composite material demonstrated that the internal energy, specifically thermal energy, of the soft PTFE matrix could be tailored by the W particle size distribution.

The effect of Mo and W additions on the magnetostriction coefficient, elastic constants and the magnetomechanical coefficient of alpha-Fe is examined by using alpha-phase Fe-Mo and Fe-Mo alloy single crystals. The W additions to Fe have provided a larger increase in magnetostriction when compared to any other non-rare-earth addition that is examined with the exception of Ga.

The tungsten filament aging when using silacyclobutane (SCB) as a source gas in a hot-wire chemical vapor deposition (HWCVD) reactor is analyzed. The studies have shown that the [H.sub.2] has etched the aged filament at high temperatures.

A first-principles calculations that models the effect of iron (Fe) atoms on the adsorption of a tungsten (W) atom on W(100) surfaces is reported. The results provide insight into fundamental mechanism that activated sintering of tungsten by Fe atoms.

The isotope-ratio and several other properties of lunar metals are measured and analyzed to explain the formation of the Moon. The findings reveal that Moon was actually formed much after the predicted time that is after the separation of the Earth's core from its mantle.

The experimental data for the shear modulus and yield strength of shocked aluminum, copper and tungsten are analyzed. The analysis concludes that the shear modulus and yield stress exhibit analogous variation with temperature and pressure for aluminum up to shock pressures of 50 GPa, copper under 100 GPa, and tungsten under 200 GPa.

Recently, researchers have observed that low silicon (Si) content in ternary nitrides of Me-Si-N (Me=Ti, Zr, Ta, W) can help in the formation of nanocomposites with enhanced hardness. But there [...]