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Flexible pipes are complex structures made of different layers and different materials. They are used in the oil and gas production in the off-shore platforms to conduct the oil or gas between different units, such as platforms, Christma's tree and transportation ships. The internal carcass of flexible pipes is made of duplex stainless steels type 2205 (UNS S32205 or S31803). In the production line, sheets of 1.8 mm thickness of this material are submitted to uncoiling and cold bending operations to form “S” profiles which are assembled to form the internal carcass. The end of one coil is welded to the begin of another, to make the process continuous. The welding process is autogenous automatic gas tungsten arc (GTAW). This work analyses the microstructure and corrosion resistance of the weld metal and compares to the base metal. Besides, non-destructive tests and electrical resistance measurements were conducted in the welded joint and base metal. The samples analyzed were from a flexible pipe manufacturer. It was concluded that the joints of this producer were not heat treated, which results in inadequate microstructure and lower corrosion resistance in the weld metal.

In the present work we have studied the effects of nitrogen addition on the equilibrium of the volume fraction ratio austenite/ferrite and on the structural properties of weldments produced by gas tungsten arc welding (GTAW). The welded joints in tubes UNS S32707 of hyper-duplex steel were produced using argon and nitrogen gas welding, with nitrogen added in ratios of 1.5, 2.5, 3.5, 4.5, and 5.5%. Microstructural characterization of this material under the different processing condition was conducted by means of optical microscopy, scanning electron microscopy, local chemical analysis by X-ray energy dispersive spectroscopy, electron backscatter diffraction Vickers microhardness test, and digital image processing. All welding conditions resulted in welded joints with equiaxial grains microstructure containing austenite both at the boundaries and in the ferrite matrix. Microhardness measurements did not show significant variation in relation to the base metal. The use of welding gases with higher percentages of nitrogen resulted in increases in the austenite volume fraction in the order of 39 to 57% when considering the nitrogen content ranging from 1.5 to 5.5%.

Statement of the problem Fixed prosthesis and partial dental prosthesis frameworks are usually made from welded Ni-Cr-based alloys. These structures can corrode in saliva and have to be investigated to establish their safety. Purpose The purpose of this study was to evaluate the corrosion behavior of joints joined by tungsten inert gas (TIG) welding and conventional brazing in specimens made of commercial Ni-Cr alloy in Fusayama artificial saliva at 37°C (pH 2.5 and 5.5). Material and methods Eighteen Ni-Cr base metal specimens were cast and welded by brazing or tungsten inert gas methods. The specimens were divided into 3 groups (base metal, 2 welded specimens), and the composition and microstructure were qualitatively evaluated. The results of potential corrosion and corrosion current density were analyzed with a 1-way analysis of variance and the Tukey test for pairwise comparisons (α=.05). Results Base metal and tungsten inert gas welded material showed equivalent results in electrochemical corrosion tests, while the air-torched specimens exhibited low corrosion resistance. The performance was worst at pH 2.5. Conclusions These results suggest that tungsten inert gas is a suitable welding process for use in dentistry, because the final microstructure does not reduce the corrosion resistance in artificial saliva at 37°C, even in a corrosion-testing medium that facilitates galvanic corrosion processes. Moreover, the corrosion current density of brazed Ni-Cr alloy joints was significantly higher ( P

In the present study we characterized titanium (Ti) surfaces submitted to different treatments and evaluated the response of osteoblasts derived from human alveolar bone to these surfaces. Five different surfaces were evaluated: ground (G), ground and chemical etched (G1-HF for 60 s), sand blasted (SB-Al2O3 particles 65 μm), sand blasted and chemical etched (SLA1-HF for 60 s and SLA2-HF for 13 s). Surface morphology was evaluated under SEM and roughness parameters by contact scanning instrument. The presence of Al2O3 was detected by EDS and the amount calculated by digital analyses. Osteoblasts were cultured on these surfaces and it was evaluated: cell adhesion, proliferation, and viability, alkaline phosphatase activity, total protein content, and matrix mineralization formation. Physical and chemical treatments produced very different surface morphologies. Al2O3 residues were detected on SB and SLA2 surfaces. Only matrix mineralization formation was affected by different surface treatments, being increased on rough surface (SLA1) and reduced on surface with high amount of Al2O3 residues (SB). On the basis of these findings, it is possible to conclude that high concentration of residual Al2O3 negatively interfere with the process of matrix mineralization formation in contact with Ti implant surfaces. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008

The aim of this research was to characterize titanium surfaces blasted with aluminum oxide (Al2O3) particles using the KS 400 digital image processing program. Samples of grade II titanium plates were submitted to blasting processes using particles of Al2O3, and treated with a hydrofluoric acid-based solution. Three digital images from each sample surface were obtained using Scanning Electron Microscopy, and half-quantitative chemical analyses were subsequently performed using Electron Dispersive Spectroscopy (EDS). In addition, parameters related to the alumina phase, such as the concentration level, the area and perimeter of the particles and their circular form factor were measured using KS 400. The mechanical/chemical treatment caused depressions up to 10 µm on homogeneous surfaces. Although the chemical attack significantly removed the alumina phase, residual particles could still be identified by the EDS. The average area occupied by the alumina phase on the samples surfaces was 469.32 (± 284.98) µm², the particle average perimeter was 81.61 (± 27.68) µm, and the mean circular form factor was 0.60 (± 0.05). Characterizing the titanium surface is essential in the evaluation of the material manufacturing process because the presence of residual aluminum particles may have deleterious effects on the formation of the osseous/implant tissue. O objetivo deste trabalho foi caracterizar parâmetros relativos a superfícies de titânio submetidas a jateamento com partículas de óxido de alumínio (alumina - Al2O3) por meio de análise e processamento digital de imagem no programa KS 400 (Carl Zeiss, Oberkochen, Alemanha). Amostras de titânio grau 2 foram jateadas com Al2O3 e submetidas a tratamento químico com soluções à base de ácido fluorídrico. Três imagens digitais das superfícies de amostras distintas foram obtidas em microscópio eletrônico de varredura. Análises químicas foram realizadas por espectroscopia por dispersão de energia (EDS). As imagens foram analisadas e processadas no KS 400 para a obtenção de parâmetros digitais e quantificação da fase residual da alumina, tais como área, perímetro das partículas e fator de forma circular. O tratamento mecânico/químico promoveu crateras de até 10 µm em uma superfície homogênea em relação ao controle (tratamento somente mecânico). O ataque químico removeu de maneira significativa a alumina, porém partículas residuais foram identificadas pela EDS. A área total ocupada pela alumina nas amostras experimentais foi de 469,32 (± 284,98) µm². O perímetro médio das partículas foi de 81,61 (± 27,68) µm e a média do fator de forma circular foi 0,60 (± 0,05). A quantificação e caracterização da superfície do titânio são fundamentais para a avaliação da fabricação dos implantes, pois a presença de alumínio residual pode provocar efeitos deletérios na formação tecidual osso/implante.