The low thickness stainless steel is widely used in the food and automotive industry and also to manufacture heat exchangers in the transport of fluids, due the stainless characteristics, in these applications the quality control of the pipe is very high, that is why it is important to achieve a strict control of the welding parameters during the manufacturing process. In order to quantify the effect of the travel speed and the hydrogen content in the shielded gas of the welding quality different test were performed with low thickness tubing's welded by GTAW process without filler material. The weld specimens were characterized by optic microscopy and scanning electron microscopy, energy dispersive x-ray spectrometry, and mechanical test like micro hardness and reverse. It was found that when the travel speed increase, a lack of penetration on the welding is observed when the hydrogen content is low, due a lower heat input.

Titanium dioxide (TiO2) is an efficient photocatalyst. It is, however, fully activated only under ultraviolet (UV) radiation. Thus some research has been addressed to modify TiO2 so that it becomes sensitive to visible (Vis) light. The aim of this work was to modify the catalytic activation wavelength of TiO2 films by N2 plasma surface treatment. For such a purpose, sol-gel method was used to coat glass substrates with TiO2 films. The films so obtained were characterized by Raman Spectroscopy and SEM. For N2 plasma treatment, the films were exposed to N2 plasma and the effect of exposure time, N2 pressure and electric conditions on TiO2 photocatalytic activity under sunlight was studied. The photocatalytic activity was established via methylene blue (MB) degradation.

Plates of Al 6063-T6 (6.35mm thick) were welded using an ER-5356 filler wire. The aim of the experiments was to assess the effects that yield the induction of an axial magnetic field (AMF) during gas metal arc (GMA) welding on the grain structure of the weld metal and on the mechanical properties of the welded joint. Magnetic fields between 0 to 15mT were induced by using a coil which was fed with different current intensities by an external power source. Plots of the grain size distribution showed that applying low magnetic fields homogenizes the grain structure of the weld metal and suppresses the typical columnar-dendritic growth from partially melted grains at the fusion line. The mechanisms involved in these phenomena are discussed with the aid of finite element analysis. Transverse microhardness profiles of the welds revealed a reduction in the loss of hardening in the heat affected zone (HAZ). The loss of hardening after fusion welding in heat treatable aluminum alloys is known as overaging and it is the result of coarsening and transformation of the strengthening phase [1]. It is thought that an electromagnetic interaction between the external magnetic field applied and the inherent magnetic field generated by the direct current of the welding process alters the diffusion process delaying over aging kinetics in the HAZ.

Texture is defined by the measured polar figure (PF) obtained from the integrated intensity of diffracted X-rays. The integrated intensity can be affected both by the pole density (PD) and by the phenomenon of extinction that reduces the PD and cannot be avoided. PF does not contain information about grain microstructure, but parameters of the primary and secondary extinction are related to the crystal microstructural features. Recently an original X-ray diffraction method was proposed for correction of PD and separation and determination of the primary and secondary extinction parameters for characterization of textured aluminum samples. This problem was solved using some assumptions. The parameter of the primary extinction can be used for calculation of domain size. The secondary extinction parameter is related to the average domain disorientation angle that depends on dislocation density in domain boundaries. Extinction parameters were used for microstructure evaluation of cold rolled nickel with and without annealing at 600°C. The validity of the proposed assumption for nickel samples was evaluated in terms of the extinction length. The corrected pole density and the parameters of primary and secondary extinction were calculated using the first order reflection for two different wavelengths (Cu and Co) and the second order reflection for one of the used wavelengths. In annealed samples the primary and secondary extinction were presented simultaneously. According to the obtained parameters of extinction the microstructure of textured nickel was evaluated.

Sodium aluminum hydroxy carbonate and potassium aluminum hydroxy carbonate, commonly named sodium dawsonite and potassium dawsonite respectively, with formula MAl(OH)2CO3 (M=Na,K), were prepared by slow evaporation of a solution obtained by dissolution of basic aluminum sulfate in 1M sodium carbonate or 1M potassium carbonate, respectively. The basic aluminum sulfate was prepared by precipitation in homogeneous solution of an aluminum bisulfite solution. The basic aluminum sulfate was dissolved in 1M sodium carbonate or 1M potassium carbonate at 80 °C. Then, the solution was heated at 60 °C in order to the crystallization of sodium or potassium dawsonite takes place. The crystallized solid was separated from the liquid by vacuum filtration and oven dried at 90 °C before to be analyzed. The synthesized powders were characterized by differential thermal analysis (DTA), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By this method crystalline sodium dawsonite and potassium dawsonite were obtained. The morphology of the particles was acicular in shape with high aspect ratio (≈267).

In this work we study the elastic-plastic transition of the spatially extended polycrystalline austenitic stainless steel 304 (SEPC-ASS-304) advanced materials during an irreversible deformation process. Such transition was characterized by means of the fractal dimension computed of a sequence of digital images of the mesostructure of the SEPC-ASS-304 surface, obtained during the elastic-plastic transition. Our results show a correlation between the fractal dimension and the evolution of the granular flow during the deformation of such advanced material.

This investigation examines the used parameters in the wet welding process, as well as his influence on the properties of welded union under manual metal arc welding process, obtained at 10m and 20m sea water deep, with an electrode E7024. The E7024 filler material is normally used in the reparation of hydrocarbon pipelines on deeps no more of 30m, however his chemical composition allow to use as material to repair in zones where the pressure is a paramount factor. A statistical design of experiments (DOE) with 36 coupons has been proposed using the travel speed, amperage and the underwater welding condition (10m and 20m) as input variables. To evaluate the quality of the welded unions, tensile, bend, hardness and metallographic test were carried out. The statistical analysis of DOE found that the amperage variable result to be the most influence parameter in the control of quality of the weld union. Besides this the technique of scanning electron microscopic was used to observe the kind of fractography showed in a crack throughout weld resulted from the bend test, and energy dispersive X-ray spectrometry to identify the present species in this zone.

The study focuses on the adhesion and friction coefficient of DLC (Diamond Like Carbon) coating on a metallic surface AISI-316L. A DC technique was used in order to develop DLC coatings, while a silicon interface allowed a better adhesion of those coatings, having variations of time during the deposit to allow different thickness in anchoring coating. The adhesion and friction coefficient were measure through Scratching Test while the sheets were analyzed through Atomic Force Microscope (AFM) to visualize its surface morphology. Besides, it was used Raman spectroscopy to study sp3/sp2 ratio of DLC coatings. The tests show that the sample with the largest period of time of deposit has a better adhesion and the highest surface roughness.

This study describes the covering process of dental burs with CVD diamond and the quality of its cut during dental procedure proving, at the same time, its advantages in comparison to regular dental burs. Ten equals burs made of tungsten carbide (WC) were covered with CVD diamond trough Hot Filament Chemical Vapor Deposition technique (HFCVD), varying thickness and temperature of deposit, leaving constant the rest of the deposit parameters like pressure (50 mbar) and gas flow (H2 and CH4). Dental cuts were comparing in a standard cutting device. The burs as well as the cuts were analyzed trough Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Analysis (EDX), what allow obtaining accurate measures of cuts and covering is chemical components. The quality and stress of the grown diamond was characterized by Raman analysis.

6201 aluminum alloy is mostly used in electrical conductors for overhead transmission lines due to its excellent mechanical and electrical properties besides to an excellent corrosion resistance. This alloy is heat treatable and the thermal treatment is performed with the objective of obtain the optimal properties for its application. In this work it was studied the effect of different deformation grades, time variation of natural aging as well as the time and temperature of artificial aging on the evolution of mechanical and electrical properties. It was found that solution treated wires at 560°C by 4h, 14 days natural aged, 92% cold deformed and artificial aged at 165°C by 7h, reach a tensile stress of 326 MPa and an electrical conductivity of 57.2%IACS (International Annealed Copper Standard).

This paper analyzes the fracture behavior and mechanisms of stress corrosion cracking (SCC) of API X52 pipeline steel. Susceptibility and mechanism of SCC was investigated using slow strain rate tests (SSRT) performed at strain rate of 1 × 10−6 in/sec in a glass autoclave containing a soil solution with pH of 8.5 at room temperature. Cathodic polarization potentials of −100, −200 and −400 mV referred to Ecorr was applied in order to establish the effectiveness of cathodic protection in mitigating SCC of X52 pipeline steel. To study the effects of several over potential in SSRT were performed at different cathodic potentials. The results of reduction area ratio (RAR), time to failure ratio (TFR) and plastic elongation ratio (PER) indicate that X52 pipeline steel was susceptible to SCC. Scanning electron microscopy (SEM) observations of these specimens showed a brittle type of fracture with transgranular appearance. The failure and SCC mechanism of X52 steel in the soil solution was hydrogen based mechanism. This mechanism was confirmed through the internal cracks observed in these specimens. All cracking tests indicated that the SCC rate was enhanced by plastic deformation.

Austenitic stainless steel HK40 is heat-resistant steel, which is used at high temperatures, used mainly in the form of castings poured by gravity into tubes used in chemical process equipment, metallurgical, petrochemical, steel therefore must resist this oxidation, carburization and sulfatation. One problem in this type of steel is the formation of brittle phases, when subjected to a temperature of 540–900 °C. The aim of this study is to determine the possible presence of M7C3 type carbide, M23C6. The tube has an outside diameter analyzed 4 inches (10.16 cm) and a wall thickness of 0.5 inches (1.27 cm). The samples used for this investigation were cut 5 specimens measures 12.5 mm in diameter and 2.25 mm in length, and underwent a heat treatment at a temperature of 680 °C for 15, 30, 45, 60 and 75 minutes with subsequent cooling in water. The samples were characterized by electron microscopy. This study was performed because the trend in the Petrochemical Industry is to reduce the wall thickness of the tubes to improve heat dissipation and reduce the residual stresses generated in the steel.

In this paper a comparative study of the hydration process in a very early age, first 20 hours, between a conventional cement paste and its equivalent with a replacement of fly ash of about 7.9%, is done. The study was undertaken through semiadibatic calorimetry, electrical impedance spectroscopy and X-ray diffraction. It shows that using electrical impedance spectroscopy we can determine the state of crystallization of the material with and without additions, thereby determining the time at which the different processes are started in the hydration

Rings produced considering industrial conditions were manufactured by ring rolling procedures. In order to evaluate the effect of heat treating on AISI 405 (UNS S40500) structure and properties, statistical software Minitab® was considered for a design of experiments involving parameters as annealing temperature and soaking time. Samples/coupons from rolled rings were annealed according design of experiments. Tensile and hardness testing was performed and reported as response surface curves after statistical analyses. Alloy characterization includes observations performed by scanning electron microscopy for evaluation of phases in order to determine alloy behavior when exposed to annealing conditions.

This study describes the influence of the processing parameters on the structure of a Diamalloy 1008 (Fe-Cr-Mo alloy) coating applied with high velocity oxi-fuel (HVOF) on steel tool grade samples D2. This coating is commonly use as a protection against corrosion and wear, but it also has the capacity to recover damaged areas as die stamping for automotive stamp. An experimental statistic design identify the fuel velocity and oxygen flow as well as the pulverization distance as the most influential parameters that control the powder particles characteristics when it’s being sprayed (“in trajectory”) before impact. The effects of these parameters in porosity level, oxide content and micro-hardness were investigated in detail. Metallographic tests are used to evaluate the deposited material adhesion quality, the SEM technique is use to evaluate the material porosity in the substrate adhesion and the damage in the tools.

In this work were evaluated the microestructural characteristics by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) of the intermetallic γ'(liquation, coarsening and decomposition) in the Inconel 939 alloy after 40000 hours and 850–900°C aging operation conditions. The alloy was vacuum conventional cast. The results show that the liquation phenomena take place in eutectics γ-γ' which are present mainly in the core of the dendritic arms and in the coarse films of carbides along the grain boundaries (GB), the γ' particles change their original morphology of ordered cuboids of 320nm to disordered and coarse cuboids of 1.2μm, carbides show a morphology change from the original dispersed particles into a coarse continuous films and particles Chinese script type, this affects adversely the mechanical properties such as creep. The results of this evaluation allow to determine the main microestructural damage mechanisms which experiment some components such as blades at high temperatures in industrial conditions.

Stress corrosion cracking (SCC) is the result of the combined influence of tensile stress and a corrosive environment on a susceptible material. This paper analyzes the understanding mechanisms of stress corrosion cracking (SCC) of API X60 pipeline steel. The susceptibility to SCC and mechanism was investigated using slow strain rate tests (SSRT). The SSRT were performed at strain rate of 25.4 × 10−6 mm/sec in a glass autoclave containing a soil solution called NS4 with pH of 3 and 10 at room temperature and 50°C. Cathodic polarization potentials of −200 mV referred to Ecorr was applied. SCC properties were evaluated by SSRT in simulated soil solution (NS4 solution) that is typical environment for SCC under cathodic charging. The results of ratio reduction area (RRA), time to failure ratio (TFR) and elongation plastic ratio (EPR) indicate that X60 pipeline steel was more susceptible to SCC at pH 3 independently of the temperature. At high pH the SCC susceptibility was higher at 50°C. Scanning electron microscopy (SEM) observations of these specimens showed a brittle type of fracture with transgranular appearance. The failure and SCC mechanism of X60 steel into NS4 solution was hydrogen based mechanism. Hydrogen absorption by X60 pipe steel may result in local corrosion (primarily, SCC) of underground pipeline steel. SEM observations revealed the presence of internal cracks in some of these specimens.

Hydrotalcite-like compounds (HLC's) are a type of ionic lamellar solids with divalent and trivalent metal cations, and exchangeable inorganic and organic anions in the interlamellar space. Interest in HLC arises from the wide applications, where thermal, structural and textural properties and as well as sorption capacity are the properties interested in. HLC are used to removal dangerous metallic anionic, such as Chromium (VI). In this study, Mg/Al - HLC's were synthesized by sol-gel method. Effect of Mg/Al was probed to show the effect on their structure, morphology, physical properties and sorption capacity. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, textural analysis and thermal analysis. Sorption profiles were investigated using batch method at initial concentration different to was determinate model and kinetic sorption capacity such as maximum removal capacity to equilibrium. Was find values of 428 and 127 mg chromates/g HLC's to Mg/Al = 2 and 7 respectively, equivalent to 125 and 57 mg of chromium /g HLC's in la little time of one minute.

In this work, silver nanoparticles were synthesized by two methods: polyol and chemical reduction using sodium borohydride (NaBH4). In both cases, silver nitrate was employed as starting metallic salt and Poly-vinyl pyrrolidone (PVP) as surfactant agent. The average nanoparticles size was correlated by transmission electron microscopy (TEM) and quasielastic light scattering (QELS). The experimental results indicate that the average particle sizes measured by QELS were slightly higher than those obtained directly by TEM. Therefore, this work confirms that the QELS technique can give rapid and approximate average-particle size values in comparison with those obtained through TEM direct observations.

The electrochemical studies of the corrosion can provide indirect techniques that they can determinate the corrosion rate of metals or alloys immersed in a corrosive medium. For many years, most studies about the cathodic and anodic polarization behaviour of metals have been confined to traditional steady-state techniques, such as potentiodynamic sweep measurements. However, steady-state techniques are limited because they give information only on the rate-determining step. Moreover, during the measuring process, technique such as potentiodynamic sweep polarize the electrode surface to such a great extent, in order to uncover corrosion mechanism, that the validity of the results can be questioned particularly in the cases when protective films. Transient electrochemical techniques such as Electrochemical Noise (EN), are less intrusive because they can provide information about the processes without disturbing the reactions with the voltage application.