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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.

No description available.

No description available.

No description available.

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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,

Aluminium alloys S1C, NS4, HE9, LM25 and the 'difficult' zinc containing U.S. specification alloy used for automobile bumpers (X-7046), have been successfully electroplated using pretreatments which utilized either conventional immersion, elevated temperature or electrolytic modified alloy zincate (M.A.Z.) deposits. Satisfactory adhesion in excess of 7•5 KN m -I was only achieved on X-7046 using an electrolytic M.A.Z. pretreatment. The limitations of simple zincate solutions were demonstrated. Growth of deposits ~as monitored using a weight loss technique and the morphology of the various deposits studied using scanning electron microscopy. The characteristics of a specific alloy and processing sequence selected had a significant influence on the growth and morphology of the N.A.Z. deposi t. These all affected subsequent adhesion of electrodeposited nickel. The advantages of double-dip sequences were confirmed. Superior adhesion was associated with a uniform, thin, fine grained M.A.Z. deposit which exhibited rapid and complete surface coverage of the aluminium alloy. The presence of this preferred type deposit did not guarantee adhesion because a certain degree of etching was essential. For a satisfactory combination of alloy and M.A.Z. pretreatment, there was a specific optimum film weight per unit area which resulted in maximum adhesion. An ideal film weight of 0•06 :!: 0•01 mg cm-2was determined for S1C. Different film weights were required for the other alloys due to variations in surface topography caused by pretreatment. S1C was the easiest alloy on which to achieve high bond strength. Peel adhesion was not directly related to tensile strength of the alloy. The highest adhesion value was obtained on S1C which had the lowest strength of the alloys studied. The characteristics of the failure surfaces after peeling depended on alloy type, adhesion level and pretreatment employed. Plated aluminium alloys exhibited excellent corrosion resistance when appropriately pretreated. The M.A.Z. layer was not preferentially attacked. There was a threshold value of adhesion below which corrosion performance ~a8 poor. Alloy type, pretreatment and coating system influenced corrosion performance. Microporous chromium gave better corrosion protection than decorative chromium.