No abstract

Wire Electrical Discharge Machining (WEDM) is one of the most important production technologies to manufacture very accurate small components and tools on any electrical conductive material. Titanium and its alloys have been widely used in automobile and aerospace industry as well as in medical engineering field. Small components and tools with complex geometrical shapes are difficult to be produced on titanium alloys by both conventional and nonconventional machining technologies. In this work an experimental investigation on the influences of wire electrode type and electrical variables when WEDM a thin plate of Ti6Al4V alloy has been carried out. Uncoated brass wire and copper wire with a diffused zinc coating were used for the experiments. Interval time, wire runoff speed, discharge duration and dielectric inlet pressure were evaluated in order to achieve adequate process parameter settings. Characteristics of surface integrity were also investigated. The best technological results for all tested WEDM parameters were attained for copper wire with a diffused zinc coating. The recast layer of the samples WEDMachined with the copper wire presented a smaller thickness and more compact than that obtained with uncoated brass wire. For WEDM with both types of wire, the existence of thermal cracks was observed.

The structural, physical–chemical, and micromechanical characteristics of Al0.6Ti0.4N coatings deposited by different physical vapor deposition (PVD) methods, such as cathodic arc deposition (CAD), as well as advanced HiPIMS techniques were investigated in terms of their cutting performance during the machining of an Inconel 718 alloy. XRD studies had revealed that the HiPIMS coating featured lower residual stresses and more fine-grained structure. Electrochemical characterization with the potentiostat-impendence method shows that the HiPIMS coating has a significantly lower porosity than CAD. SEM and AFM studies of the surface morphology demonstrate that the HiPIMS coating has a smoother surface and an absence of droplet phases, in contrast with CAD. XRD, combined with FIB/TEM studies, shows a difference in the crystal structure of both coatings. The micromechanical characteristics of each coating, such as hardness, elastic modulus, fracture toughness, and adhesion to the substrate, were evaluated. The HiPIMS coating was found to possess a more beneficial combination of micromechanical properties compared to CAD. The beneficial characteristics of the HiPIMS coating alleviated the damage of the coated layer under operation. Combined with grain size refinement, this results in the improved adaptive performance of the HiPIMS coating through the formation of a greater amount of thermal barrier sapphire tribo-films on the friction surface. All of these characteristics contribute to the reduction of flank and crater wear intensity, as well as notching, leading to an improvement of the HiPIMS coating’s tool life.