Current Issue : July-September Volume : 2023 Issue Number : 3 Articles : 5 Articles
In this study, corrosion-resistant AA5083—BN/WC composites were developed for tribological applications through adequate control of the reinforcement content (WC and BN) in the matrix (AA5083 alloy). The effects of 6% and 12% tungsten carbide (WC) as well as 6% and 12% boron nitride (BN) additions on the corrosion behavior of AA5083 aluminum composite in 3.5% NaCl solution were carried out. Electrochemical techniques such as cyclic potentiodynamic polarization (CPP), changes in the chronoamperometric current with time (CCT), and electrochemical impedance spectroscopy (EIS) were utilized. The polarization results showed that the addition of 6% WC to the AA5083 alloy matrix improved its resistance to corrosion (RP). Rp exhibited an additional increase by adding 12% WC to the matrix. The values of RP were observed to increase for the AA5083 composite when adding 6% BN, and the highest RP values were recorded for the composite that contains 12% BN. The results obtained by the CPP method were confirmed by CCT and EIS measurements, where the presence of WC and BN protected the developed AA5083- BN/WC composites against corrosion. The corrosion resistance revealed an additional improvement with an increase in WC and BN content from 6% to 12%. The results also confirm that pitting corrosion decreased in the presence of WC and BN in the fabricated composites....
The effect of tungsten, aluminum, and cobalt on the mechanical properties of iron‐based composites prepared by powder technology was studied. Five samples with different contents of tungsten, aluminum, and cobalt were established. The five samples have the following chemical compositions: (I) full iron sample, (II) 5wt.% tungsten, (III) 5wt.% tungsten‐4wt.% cobalt‐1wt.% aluminum, (IV) 5wt.% tungsten‐2.5wt.% cobalt‐2.5wt.% aluminum, and (V) 5wt.% tungsten‐1wt.% cobalt‐ 4wt.% aluminum. The mixed composite powders were prepared by mechanical milling, in which 10:1 ball to powder ratio with 350 rpm for 20 h was cold compacted by a diaxial press under 80 bars, then sintered at temperatures ranging from 1050 °C to 1250 °C in an argon furnace. The samples were characterized mechanically and physically using XRD, SEM, a density measuring device, a hardness measuring device, a compression test device, and a tribological device for wear and friction tests. XRD results refer to the formation of different intermetallic compounds such as Fe7W6, Al5Co2, Fe2W2Co and Co7W6 with the main peaks of Fe. The good combination of tribological and mechanical properties was recorded for sample number five, which contained 5% W, 4% Al, 1% Co and Fe base, where it obtained the highest wear resistance, largest hardness, acceptable compressive strength, and lowest friction coefficient due to the good combination of hard and anti‐friction intermetallic action compared with the other samples. This sample is a good candidate for applications which require high wear resistance and a moderate friction coefficient accompanied with high toughness, like bearing materials for both static and dynamic loading with superior mechanical and tribological properties....
The DLC film was prepared on a nitrile rubber (NBR) elastomer by DC magnetron sputtering (DC-MS), and the sp3 ratio of the DLC film was adjusted by changing the negative bias voltage applied to the substrate. The microstructure, composition, and tribological properties of the DLC films deposited on NBR substrates were systematically investigated. The results reveal that the DLC film on the NBR surface can protect the NBR and reduce the surface roughness of the NBR. While the bias voltage ranges from 0 V to −150 V, the content of sp3 increases with an increase in the negative bias voltage. The viscoelasticity and roughness of the NBR substrate will greatly affect the DLC film’s adhesion strength and tribological behavior....
The applications projected in the coatings are in implants with the lower extremities since they require a great load capacity and are essential for walking. Therefore, the use of devices or implants is necessary for recovery, osteosynthesis, and fixation. The tribocorrosive behavior of nanostructured compounds based on titanium oxide with an intermediate layer of gold deposited on titanium substrates was determined. These coatings were obtained using the reactive magnetron sputtering technique. Tribocorrosive properties were evaluated at sliding speeds of 3500 mm/min, 4500 mm/min, 6000 mm/min, 7500 mm/min, and 9000 mm/min with loads of 1 N, 2 N, 3 N, 4 N, and 5 N. The coatings were characterized by X-ray photoemission spectroscopy and X-ray diffraction, and the surface roughness was analyzed by atomic force microscopy. The dual mechanical and electrochemical wear tests were carried out with a potentiostat coupled to a pin on the disk system. The system was in contact with a hanks solution (37 ◦C), which acted as a lubricant. Structural characterization made it possible to identify the TiO2 compound. In the morphological characterization, it was found that the substrate influenced the surface properties of the coatings. The tribological behavior estimated by the wear rates showed less wear at higher load and sliding speeds. It was shown that it is possible to obtain coatings with better electrochemical and tribological performance by controlling the applied load and slip speed variables. In this study, a significant decrease corresponding to 64% was obtained, specifically in the speed of deterioration, and especially for a load of 5 N, depending on the sliding speed that went from 0.2831 mpy (Mils penetration per year) to 3500 mm/min compared to 0.1045 mpy at 9000 mm/min, which is explained by the mechanical blockage induced by the coating....
The development of advanced machining techniques requires high-performance tool coatings. To improve the wear resistance and cutting performance of AlTiN coatings, a structure optimization strategy involving bias control and a nano-multilayer architecture strategy is presented. The investigated AlTiN coatings were deposited by cathodic arc evaporation and studied with regard to phase structure, hardness, adhesion, and tribological properties by a combination of Xray diffraction, nanoindentation, scratch, and ball-on-disk friction tests. A high bias potential (up to −120 V) with enhanced adatom mobility suppressed the formation of the wurtzite structure AlN in AlTiN. In addition, the epitaxial growth of Al0.67Ti0.33N on Al0.5Ti0.5N in the AlTiN nanomultilayer could also promote the single-phase structure. The hardness of AlTiN-based coatings with a dominated cubic structure was 3–4 GPa higher than conventional ones. In addition, the interlayer interfaces in the Al0.67Ti0.33N/Al0.5Ti0.5N multilayer could deflect the cracks and thus improve the fracture toughness. As a consequence, the Al0.67Ti0.33N/Al0.5Ti0.5N multilayer with enhanced mechanical properties obtained the lowest wear rate of 1.1 × 10−5 mm3/N·m and the longest cutting lifetime of 25 min during dry turning the SUS304 stainless steel....
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