In recent years demand from production industry for high performance cutting tools, aero and automobile engine parts has prompted research into both existing and novel methods of laying down hard, low friction coatings . A key process for the production of such coatings has been Physical Vapour Deposition (PVD) which has proved to be a consistent and reliable tool for industry. For this technique to continue to be improved and more advanced coatings to be produced, research at the fundamental level is required. This thesis describes research investigating the behaviour of the steered arc cathode spot and methods of improving existing steered arc coating technology. The majority of existing steered arc systems use either permanent magnets or a combination of permanent and electromagnets to steer the arc. Described here is a novel system which employs a pair of electromagnetic coils of cylindrical geometry which enable the arc to be positioned on a circular orbit through a range of continuously variable radii. In addition to this the coils are capable of controlling the transverse and normal magnetic field profiles independently of the steering radius selected. This enables the behaviour of the arc spot to be investigated under a range of magnetic field conditions thus allowing the comparison of measured arc behaviour with a new model of arc motion. Care has described the motion of the arc spot as a biased random walk and has derived an analytical solution to describe the time dependent, probability density function for the arc position in two dimensions. Two distributions are proposed (one in each dimension); the first describes the probability density for the arc position in the direction of driven motion, the second the probability density in the direction of arc confinement. The shape of these distributions is dependent upon the transverse and normal components of the applied magnetic field. A series of experiments are described here that measure the shape of these distributions as a function of either magnetic field, cathode material or both. In the case of the distribution of the arc position in the direction of confinement the width of the distribution is measured as a function of normal and transverse field components. In the direction of steered motion, distributions of arc orbital transit times are measured for a number of cathode materials: analysis of these distributions allow the determination of a mean macroscopic spot velocity and the spot diffusion coefficient. In both cases comparison with Care's model reveals good agreement between experiment and theory to the limits of the experimental apparatus. A further experiment was also conducted to test the prediction that the diffusion coefficient (measured in the direction of steered motion) is independent of the applied field. In this case results are inconclusive and further work is recommended. The mean spot velocity and diffusion coefficients for four materials were measured; titanium, zirconium, aluminium and 316 stainless steel. The results for aluminium and stainless steel compared favourably with some measurements performed by other workers, whilst those for titanium and zirconium are new results with no data available for comparison.

Ceria (CeO2), chromia (Cr2O3), yttria-stabilized zirconia (Y2O3-ZrO2), and sodium cerium oxide (Na2CeO3) were used as barrier coatings on Ufala, an alumina-based ceramic refractory, to determine if they were effective at increasing the life of the refractory in a high-temperature black liquor gasification environment. The ceria, chromia, and yttria-stabilized zirconia coatings were applied at atmospheric pressure using a coating applicator at the Institute of Paper Science and Technology at the Georgia Institute of Technology. The sodium cerium oxide coatings in addition to the three other coating types were applied under atmospheric pressure at C3 International Technologies in Alpharetta, GA. The coated refractory, as well as a set of uncoated refractory used for baseline analysis, were tested using molten synthetic smelt at 1000C for 36 hours. Uncoated refractory samples were also tested for 12, 72, 120, and 168 hours in order to make a kinetic reaction rate determination. The refractory were analyzed using gravimetric and dimensional analysis, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy to determine the severity of the physical changes that occurred after exposure to molten smelt. The data gathered from these experiments were not able to conclude that barrier coatings are sufficient to impede corrosion of the Ufala refractory material in molten smelt.

The aim of this thesis is a complex processing of obtained technical findings in the area of cutting materials, especially the evaluation and comparison of work possibilities recommended by prime world manufacturers for effective usage and application of coated and uncoated cemented carbides. Characteristics of cemented carbides in terms of production, marking method, physical and mechanical properties and application. Comparison of cemented carbides in the range of production of the most significant world tool and cutting material producers. Cutting efficiency evaluation of the tool. Recommended areas and operating conditions for effective usage of cemented carbides and their technical economic evaluation.

The thesis is focused on the characteristic of coating methods and their division, on the morphology of defects and cause of wear in coated cutting tools of sintered carbides. The experimental part is focused on a comparing cutting performance testing of indexable cutting inserts coated with nanocrystaline composite TiAlSiN at the longitudinal turning.

The thesis focuses on the morphology of defects and cause of wear in coat cutting tools, the description of the chip formation and its effects on the machined area. The experiment drala with the description of the chip form in connection with the cutting properties, type of tools, wear in removable parting cutting tips and the comparison of cutting tips from two leading manufacturers.