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Under ideal conditions ion plating produces finely grained dense coatings with excellent adhesion. The ion bombardment induced damage initiates a large number of small nuclei. Simultaneous coating and sputtering stimulates high rates of diffusion and forms an interfacial region of graded composition responsible for good adhesion. To obtain such coatings on components far industrial applications, the design and construction Of an ion plater with a 24" (O.6rn) diameter chamber were investigated and modifications of the electron beam gun were proposed. A 12" (O.3m) diameter ion plater was designed and constructed. The equipment was used to develop surfaces for solar energy applications. The conditions to give extended surfaces by sputter etching were studied. Austenitic stainless steel was sputter etched at 20 and 30 mTorr working pressure and at 3, 4 and 5 kV. Uniform etching was achieved by redesigning the specimen holder to give a uniform electrostatic field over the surfaces of the specimens. Surface protrusions were observed after sputter etching. They were caused by the sputter process and were independent of grain boundaries, surface contaminants and inclusions. The sputtering rate of stainless steel was highly dependent on the background pressure which should be kept below 10-5 Torr. Sputter etching improved the performance of stainless steel used as a solar selective surface. A twofold improvement was achieved on sputter etching bright annealed stainless steel. However, there was only slight improvement after sputter etching stainless steel which had been mechanically polished to a mirror finish. Cooling curves Were used to measure the thermal emittance of specimens. The deposition rate of copper was measured at different levels of power input and was found to be a maximum at 9.5 kW. The diameter of the copper feed rod was found to be critical for the maintenance of a uniform evaporation rate.

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A range of plain carbon, carbon-m~mganese cmd low alloy cast, steels were tested in order to determine their Various fracture toughness values under elastic and elastic-plastic conditions. The main fracture toughness parameters which are considered are (1) Linear Ilastic Fracture Mechanics (LEFM), (2) the J-Contour Integral, and (3) Crack Opening Displacement (COD). Rasults are obtained from fracture toughness specimens of various dimensions and the relevance of the validity criteria to cast steels is considered in some detail, In addition, the effect of casting position on specimen toughness values was noted. Valid K1C results according to LEFM, were obtained for three of the eight cast steels tested. Although KIC values from LEFM were not; obtained from the remaining five steels, critical COD and J -integral values were determined. It is postulated that these value and particularly the critical J values can be used, with confidence ,for material selection or in defect tolerance calculations using these steels. Toughness values were found to vary with casting position in several of the steels tested and the possible reasons for such variations are discussed in the Thesis,