A Comparative Experimental Study on Machining Performance of Aluminium against Advanced Diamond Coated Cutting Tool Inserts

Carbide tools with mono/multilayer coating such as TiN, TiC, TiAIN, TiB2 and Al2O3 on inserts of WC-Co generated key success for machining of ferrous materials without coolant/lubrication. So far dry machining of aluminium, manufacturing industries such as automobile and aerospace engineering are facing considerable challenges. Exploration of correct cutting tool for machining of aluminium still persists in the present day context. This paper experimentally investigated the affinity and performance of different cutting tool materials available in local tool shopping center along with the diamond coated tool insert prepared and developed in our own HFCVD reactor for machining of aluminium in dry condition. Finally it is revealed that, due to the low chemical affinity, small magnitude of cutting force, chemical inertness and remarkable anti-welding characteristics, diamond coated tool displayed improved performance as compared to other tools.

Characterization of TiZrN and TaZrN Nanocomposite Multilayer Coating Deposited via RF/DC Magnetron Sputtering on AISI4140 Steel

In this present research work, TiZrN and TaZrN multilayer coating was deposited on 4140 steel by RF/DC magnetron sputtering for comparative work also prepared in single layer. The flow rate ratio of Ar/N2 was set to 15 : 3 sccm and the thin film was prepared by the PVD (physical vapor deposition) method by RF/DC magnetron using a Ti-Zr and Ta-Zr target with a purity of 99.99%. The crystal structure, surface morphology microstructure, and component arrangements were explored by X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscopy (AFM). It has been found that the crystal structure, surface morphology, microstructure, and elemental composition of the membrane are strongly dependent on deposition parameters. It is mechanically characterized by corrosion and Vickers hardness. In AFM measurements, coarse cluster particles with increasing Ti and Ta values not only increase the average roughness (Ra) by 2.341 nm (200°C) and 2.951 nm (400°C) but also have a continuous average thickness which was shown to increase by 1.504 nm and 781.75 nm. With the increase of hardness, the roughness decreases correspondingly. The TiZrN multilayer microhardness augmented to 314 GPa at 200°C and 371 GPa for TaZrN (400°C).

Increasing the tribological properties of the sur-face layer of cast iron by treatment in the envi-ronment of overheated steam of aqueous solution

The formation of the surface layer of cast iron during the processing of cast iron in the environment of superheated steam of an aqueous solution of salts is considered. An ecologically cleaner method of chemical-thermal treatment is offered. The article considers the surface layer obtained in the environment of superheated steam of an aqueous solution of water-soluble salts of ammonium molybdic acid. The layer is formed on the surface of the matrix and around the graphite inclusions. The impact of temperature on the formation of a multilayer coating by increasing the temperature in contact with the metal surface is the dissociation of chemical compounds in solution, with the formation of atomic oxygen, sulfur, nitrogen, molybdenum. The formation of the surface layer occurred not only on a metal base, but also on the boundaries of graphite, both lamellar and globular, coming to the surface of the metal without breaking the solid layer. It is established that as a result of interaction of technological parameters of temperature, holding time and concentration of saturated medium graphite in the surface layer changes its shape, becoming spherical, although in the matrix it had a lamellar shape. It is multiphase and contains soft and hard structural components. Comparative studies have shown that the wear rate of untreated cast iron is much higher than that of treated cast iron, and reaches 0.8 ∙ 10-4 μm/km at a load of 400 N. This increases the wear resistance of cast iron and at the same time improves the workability reducing the coefficient of friction. The effect of the coating on the workability show that the stabilization of the friction moment occurs faster in samples with a multilayer coating. Thus, for gray cast iron with lamellar graphite, the stabilization time of the friction moment in a multilayer coating is 0.6 h compared with 2 h for a single layer coating; in high-strength cast iron it is, respectively, 5.2 and 6.3 hours.

Study on Performance of PVD AlTiN Coatings and AlTiN-Based Composite Coatings in Dry End Milling of Hardened Steel SKD11

Dry milling of hardened steel is an economical and environmentally friendly machining process for manufacturing a mold and die. Advances in coating technology makes the dry milling a feasible approach instead of a traditional grinding process. However, the cutting condition is particularly severe in a dry machining process. High-performance coating is desired to meet the requirement of green and highly efficient manufacturing. This study concerned the performance of AlTiN-based coatings. The effect of Al content, and the AlTiN composite coating on the cutting performance of tools are investigated in terms of friction force at the tool–chip interface, specific cutting energy, cutting temperature on the machined surface, tool wear pattern and mechanism, and surface integrity. The results show that advanced AlTiN-based coatings reduce the force and cutting energy and protect the cutters from the high cutting temperature effectively. The main wear mechanisms of the coated tools are adhesive wear, chipping induced by fatigue fracture and abrasive wear. In general, the dry milling of hardened steel with AlTiN-based coatings gains a quite satisfactory surface quality. Furthermore, AlTiN-WC/C hard-soft multilayer coating performs well in reducing cutting force, preventing adhesion wear and isolating the cutting heat, being suitable for dry milling of hardened SKD11.

Control of Specific/Nonspecific Protein Adsorption: Functionalization of Polyelectrolyte Multilayer Films as a Potential Coating for Biosensors

Control of nonspecific/specific protein adsorption is the main goal in the design of novel biomaterials, implants, drug delivery systems, and sensors. The specific functionalization of biomaterials can be achieved by proper surface modification. One of the important strategies is covering the materials with functional coatings. Therefore, our work aimed to functionalize multilayer coating to control nonspecific/specific protein adsorption. The polyelectrolyte coating was formed using a layer-by-layer technique (LbL) with biocompatible polyelectrolytes poly-L-lysine hydrobromide (PLL) and poly-L-glutamic acid (PGA). Nonspecific protein adsorption was minimized/eliminated by pegylation of multilayer films, which was achieved by adsorption of pegylated polycations (PLL-g-PEG). The influence of poly (ethylene glycol) chain length on eliminating nonspecific protein adsorption was confirmed. Moreover, to achieve specific protein adsorption, the multilayer film was also functionalized by immobilization of antibodies via a streptavidin bridge. The functional coatings were tested, and the adsorption of the following proteins confirmed the ability to control nonspecific/specific adsorption: human serum albumin (HSA), fibrinogen (FIB), fetal bovine serum (FBS), carcinoembryonic antigen human (CEA) monitored by quartz crystal microbalance with dissipation (QCM-D). AFM imaging of unmodified and modified multilayer surfaces was also performed. Functional multilayer films are believed to have the potential as a novel platform for biotechnological applications, such as biosensors and nanocarriers for drug delivery systems.

Optical fluxes propagation in the planar transport layer of multilayer coatings

The article is concerned with peculiarities study of the quasimonochromatic optical fluxes propagation through thin planar transparent layer of multilayer coating. There is shown that these fluxes can be transported by the layer in process of its multiple consequtive total internal reflection or by the waveguide-resonance propagation manner depending on correlation between the layer width and the radiation coherence length half of transported fluxes. Efficiency comparison of these radiation transportation mechanisms showed that the waveguide-resonance propagation approach is more adequate for results description of the optical waveguides functioning. It allowed to conclude that optical waveguides (fibers) function in frame of the waveguide-resonance paradigm and the waveguide-resonance mechanism is responsible for the light fluxes transportation on great distances.