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A total number of 100 Nile tilapia (Oreochromis niloticus) were collected from Edco private fish farms in Behiera governorate during the period between July and September 2013 and screened for branchiomyces infection. The infected fish were suffering from respiratory distress (resulted from gill tissue damage); gasping air from the water surface, rapid movement of operculum and massive mortality, which resulted in the loss of 90% of the collected fish. Squash preparations from the infected gill tissue revealed brown, broad, branched and non-septated hyphae. On Sabouraud's dextrose agar (SDA) media with 10% duck decoction showed bright white colonies after 2 days which reached its maximum growth 8 days post inoculation. Microscopical examination of stained growth with Lactophenol cotton blue, branched hyphae at their tips were identified which were characteristic for Branchiomyces sp. The causal pathogen was identified as Branchiomyces demigrans, in which the diameter of spores and non-septated hyphae were 4-10 μm and 16-24 μm, respectively. The fungus was confirmed using polymerase chain reaction (PCR). Experimental infection and rei-solation of fungus revealed the same findings of natural infection. Clotrimazole was more effective than clove oil, while using both of them revealed higher lysozyme activity and phagocytic activity. Histopathological examination from naturally and experimentally infected fish gills revealed non-septated hyphae and spores were embedded in between affected gill tissues, which confirmed that the isolated organism was Branchiomyces demigrans

Poor surface quality represents one of the most critical drawbacks of metal parts produced by powder bed-based Additive Manufacturing (AM) technologies, such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). Among the several post-process surface finishing treatments, Fluidised Bed Machining (FBM) could represent an intriguing and cost effective option for the treatment of complex AM metal parts. This work illustrates the results of the preliminary tests carried out by means of the FBM technology in which an external contribution of rotational speed of the samples was introduced. Rotation of the samples was considered in order to increase the relative speed and energy dissipation between the parts and the fluidised abrasive particles, with the aim to increase the process efficiency in terms of surface roughness reduction. For the experiments, AlSi10Mg alloy square flat samples were built in vertical direction by means of SLM technology and dipped into an abrasive fluidized bed of silica sand. The preliminary tests were carried out by adopting a minimum fluidization regime of the abrasives and establishing, through the rotation of the samples, two values of mean superficial tangential speed of 1 m/s and 2 m/s. The effect of the latter was investigated in combination with different impact angles, considering a process time of 30 min. The surfaces were characterized quantitatively by means of confocal microscopy and weight loss measurements, while SEM images were acquired in order to observe the real morphology evolution after the treatment. The experimental results suggested a slight surface modification and roughness reduction for the investigated FBM process conditions, due to a low energy transfer from the abrasives to the surfaces. On the other hand, the results shown also that a greater surface smoothing effect was achieved when increasing the tangential speed and adopting low impact angles.

Additive Manufacturing (AM) can be considered today as a real production technology, which allows to realize parts with a complexity degree that, in some cases, is not achievable otherwise. However, one of the most relevant weak spots is the high surface roughness, especially for metal parts, making necessary the adoption of post-process finishing treatments. This paper deals with the preliminary investigations on the Fluidised Bed Machining (FBM) technology, in which a sample is dipped into a fluidized bed, i.e. a two-phase system where an abrasive, kept in motion through a gas, behaves like a fluid performing a huge number of impacts on the considered surface. This peculiarity could guarantee a high degree of homogeneity of the treated surface morphology. The influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime. The treatment has been carried out by dipping the samples for a total time of 3 hours and monitoring the results with a step of 30 min for the first 2 hours. The treated surfaces have been characterized by means of Confocal Microscopy and Scanning Electron Microscopy (SEM). Weight loss measurements have been carried out as well for a preliminary evaluation of wear. Results suggest a poor decrease in surface roughness (Sa), as also demonstrated by the poor weight loss, both due to a low impact energy of the abrasives. However, variations of other surface texture parameters (Sz, Ssk, Sku, Rdq), as well as SEM images, suggest that the main surface-abrasive flow interaction phenomena are micro-ploughing and micro-peening.Additive Manufacturing (AM) can be considered today as a real production technology, which allows to realize parts with a complexity degree that, in some cases, is not achievable otherwise. However, one of the most relevant weak spots is the high surface roughness, especially for metal parts, making necessary the adoption of post-process finishing treatments. This paper deals with the preliminary investigations on the Fluidised Bed Machining (FBM) technology, in which a sample is dipped into a fluidized bed, i.e. a two-phase system where an abrasive, kept in motion through a gas, behaves like a fluid performing a huge number of impacts on the considered surface. This peculiarity could guarantee a high degree of homogeneity of the treated surface morphology. The influence of the impact angle has been investigated by conducting experiments with AlSi10Mg plates made by Selective Laser Melting Technology (SLM), and the fluidized bed operated in bubbling fluidization regime. The treatment has been carried out ...

The effects of different heat treatments on Inconel 718 parts produced through selective laser melting were investigated. Different heat treatments, carried out by varying both temperature and time, were performed on 10x10x10 mm3 cubes. Aiming to study the effects of the treatments, microhardness measurements, optical and SEM observations were carried out on both the treated and the untreated samples. The results obtained proved the effectiveness of the treatment, if the conditions are properly set, in producing the typical microstructure of the cast Inconel 718 that is the starting point for the conventional heat treatments. A predominant influence of the temperature was also highlighted.The effects of different heat treatments on Inconel 718 parts produced through selective laser melting were investigated. Different heat treatments, carried out by varying both temperature and time, were performed on 10x10x10 mm3 cubes. Aiming to study the effects of the treatments, microhardness measurements, optical and SEM observations were carried out on both the treated and the untreated samples. The results obtained proved the effectiveness of the treatment, if the conditions are properly set, in producing the typical microstructure of the cast Inconel 718 that is the starting point for the conventional heat treatments. A predominant influence of the temperature was also highlighted.

Metal spinning is one of the oldest sheet metal forming processes, which involves a simple tooling and a spinning lathe, whatever manual or computer numerical controlled. However, for its high flexibility and the possibility to produce thin wall sectioned near net shape parts in a very cheap way, sometimes with high complexity geometries, could be revived as an interesting alternative in many applications fields such as automotive and aerospace, whereas other sheet forming processes like deep drawing does not match costs requirements for little dimension production batches. In this work, the production of a flame tube head sector prototype using an AISI 304L stainless steel is proposed, in order to evaluate the process feasibility for the required part geometry. The prototype production was carried out using a two-stage semiautomatic spinning process, starting from a 1mm thick sheet. No preheating of the sheet was adopted to enhance its ductility. The process effects in terms of wall thickness reduction, and hence in cold working, were investigated. Using optical microscopy and Scanning Electron Microscopy (SEM) techniques, the microstructural behavior of the metal subjected to the forming process was investigated, while for an evaluation of the hardness variation Vickers micro-indentation tests were performed. The main result of the process, as observed from all the investigation techniques adopted, is the formation of strain induced martensite, due to the severe plastic deformation and cold reduction of the material, ranging in this case from 30% to 50%. In some areas of the part section, some rips indicating an excessive tensile stress were also detected.

The additive manufacturing technologies are finding an increasing use due to their peculiarities. A limit that still hampers their massive application is the maximum dimension of the components than can be produced. This paper deals with the study of the joining process of additive manufactured parts. In particular, two different cases have been studied: i) Ti6Al4V parts made through electron beam melting joined through linear friction welding; ii) AlSi10Mg parts made through direct metal laser sintering joined through friction stir welding. The results obtained showed the feasibility of both the processes.