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A detailed study has been made of titanium carbide (TiC) coatings chemically vapour deposited on powder metallurgy (PM) BT42 grade high speed steel (HSS) indexable cutting tool inserts, in collaboration with Edgar Allen Tools, Sheffield. Initially, the characteristics of a TiC coating deposited under the standard conditions employed by Edgar Allen Tools were determined, both before and after the obligatory HSS substrate heat treatment. This was done using various techniques including x-ray diffraction, scanning electron microscopy, micro-hardness testing, profilometry, optical microscopy and scratch-adhesion testing. Although the characteristics of the TiC coating were found not to be significantly affected by the HSS substrate heat treatment, some of them were different to those presented in the literature for TiC coatings chemically vapour deposited on cemented carbide substrates. A comprehensive survey of the literature revealed that the process parameters employed during the chemical vapour deposition (CVD) of TiC coatings, particularly the CHy/TiCly mole ratio and deposition temperature, have a significant effect on coating characteristics. Consequently, it was decided to investigate the effect of these parameters on the characteristics of the TIC coatings chemically vapour deposited on the PM HSS inserts and, further, their effect on the tool lives exhibited by the coated inserts. The latter were determined from a series of turning tests on 817M40 workpiece material, carried out under conditions of builtup- edge (bue) formation, at cutting speeds in the range 37.5 - 60 m min 1. Both process parameters were found to have a marked effect on the characteristics of the TiC coatings and on the tool lives exhibited by the coated inserts. The reasons for this are discussbd. The TiC coated inserts which displayed the most favourable combination of coating characteristics and tool life were used in two further series of turning tests carried out to investigate tool wear, bue size, tool forces, apparent coefficient of friction and workpiece surface finish. Uncoated inserts were also tested. The application of the TiC coating was found to have led to a marked improvement in the cutting properties of the PM HSS inserts. Its role during cutting was studied from metallographic sections through worn inserts and the reasons for its effect on cutting properties are discussed.

General: The thesis concerns the prediction and control of vibrations in planar, kinematically determinate linkage mechanisms operating in a continuous manner, typically driven by a crankshaft. An array of simplified models of linkage components is used to assess the likely significance of the many factors concerned, assuming the components to be of realistic proportions. It is concluded that the effects of joint clearance and (in some cases) driving system flexibility, rather than link flexibility per-se, are likely to be the crucial factors. Attention is therefore focused on the former factors in the chapters that follow. Clearance Effects: The literature on the two-dimensional dynamic effects of clearance("ludodynamic" effects) in revolute joints is critically reviewed, with the conclusion that existing theoretical models need to be simplified to be of use for preliminary design synthesis, and that more discriminating experimental work is needed before any of the theories can be applied with confidence. A new theory is developed with a view to meeting the former need, the results being presented in the form of a design chart. An account is then given of the design, development and use of a novel experimental apparatus for studying a number of relevant aspects of the ludodynamic behaviour of a revolute joint. The new theory is supported in some respects for'larger clearances (250 um on 50mm diameter) but for smaller clearances (65 & 20 pm) the air 'squeeze film' is found to play an increasingly dominant role. Drive Flexibility Effects: The effects of driving system flexibility are approximately governed by an inhomogeneous Hill's equation. A numerical method is used to find the harmonic composition of the steady state solutions of this equation. A rule for predicting resonant and unstable speeds is hypothesized: it is shown to give excellent results, but the response at off-resonant speeds also has a large high-frequency element in some cases. Synthesis: A convenient method for modifying undesirable dynamic performance in a linkage mechanism is the attachment of auxiliary masses or springs. A method is developed for the efficient optimisation of counterweights by a weighted root mean square criterion, subject to bounds on the physical parameters. A known method for synthesis of auxiliary springs by the use of precision points in the objective function is extended, and methods for optimising the spacing of the precision points are introduced.

Due to limitations of cutting picks in terms of rock strength and abrasivity, the application of present day boom type partial-face tunnelling machines is restricted. It seems that the performances of these machines can be improved considerably by hybridizing cutting picks with high pressure water jets. There are many questions that needs to be answered before an excavation machine incorporating high pressure water jets and mechanical tools can be used to excavate rock most efficiently. Amongst these questions are; the selection of optimum water jet pressure and nozzle diameter, the influence of nozzle positioning with respect to mechanical tool e. g. side-off, lead-on, stand-off distances, cutting speed and number of passes of the Jet. The research described in this thesis examines the effect of the above variables on the performance of a hybrid cutting system, together with a comparision of mechanical and hybrid cutting systems in terms of tool forces, yield and specific energies recorded for seven rock types. Small scale qualitative finite element stress analysis was also carried out to analize the stress field around the mechanical tool tip to provide an insight into the mechanics of rock failure under high pressure water jet assisted cutting.