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Ternary Ni-W-P films were produced by electroless deposition using baths with different tungsten concentrations. After deposition, the coated surfaces were annealed at 400°C for 1h. Surface morphology and film composition in the as-plated condition were assessed by SEM and EDS analyses, respectively. The crystalline phases after annealing were investigated by X-ray diffraction (XRD). Nanoindentation tests were performed to assess the mechanical properties of the deposited films. Surface roughness was determined by confocal laser scanning microscopy (CLSM). Friction coefficient was evaluated by reciprocating were tests in a nanotribometer. The corrosion behavior was evaluated by potentiodynamic polarization curves. The results showed that the surface morphology, crystallization behavior and corrosion resistance were affected by the tungsten content in the film. The best corrosion performance was obtained for the ternary films after annealing. Hardness, surface roughness and friction coefficient were dependent of the tungsten concentration in the film.

a b s t r a c tBetween the Late Carboniferous and Early Triassic, the southwestern Gondwana supercontinent was characterized by the development of a huge intracratonic basin. A large confined epeiric sea and the accumulation of a transgressive-regressive sequence were formed by continuous subsidence related to tectonic effects caused by the Sanrafaelic Orogeny and the consequent generation of accommodation space. The Permian Rio do Rasto Formation documents the last progradational cycle related to the complete continentalization of this epeiric sea. The basal member of the Rio do Rasto Formation (Serrinha) is believed to have been deposited in a shallow epicontinental water body subjected to storms and influenced by episodic deltaic incursions. One of the most remarkable characteristics of the Serrinha Member is the presence of carbonate concretions hosted in mudstones and very fine sandstones. Here, we combine sedimentological and petrographic descriptions coupled with geochemical and stable carbon and oxygen isotopic data to elucidate the nature of these carbonate concretions. The nondeformed internal structure, decreasing proportion of carbonate cements relative to detrital grains toward the concretion edges, core-to-rim isotopic variations, and perhaps most importantly, the preservation of a welldeveloped cardhouse fabric support an early diagenetic origin for these structures at shallow burial depths of tens of meters. Stable isotope analyses of micritic calcite cements and calcites filling the septarian fractures reveal major negative excursions in both δ 18 O and δ 13 C values. Oxygen isotope ratios obtained for the micritic calcite cements vary between −12.1 and −2.6‰. The calcite filling septarian fractures also exhibit negative values of δ 18 O (− 14.2 to −13.8‰), with an average of − 14‰. The δ 13 C values of micritic calcite cements range from − 5.0-0.2‰. The carbon isotopic data from the calcite-filling septarian fractures are also negative (− 4.4 to −3.3‰). The δ 18 O signatures suggest that the early diagenetic carbonate concretions precipitated in a shallow freshwater environment rather than in a marine setting. The δ 13 C values suggest that the carbon isotopes were derived from a source with slightly depleted 13 C, supporting at least a partial organogenic contribution with weak sulfate reduction rates typical of freshwater systems. Sedimentological analysis shows that the epicontinental water body in which the Serrinha Member was deposited was constantly supplied by rivers and meteoric waters, which suggests that an enormous freshwater basin with restricted marine connections to the Panthalassa Ocean once existed.

The aim of the present work was to study the passive film stability and pitting corrosion behavior of the AISI 409 stainless steel. The electrochemical tests were carried out in 0.1 M NaCl solution at room temperature. The general electrochemical behavior was assessed using electrochemical impedance spectroscopy (EIS) measurements whereas the semiconducting properties of the passive film were evaluated by the Mott-Schottky approach. Pitting corrosion was investigated using potentiodynamic and potentiostatic polarization tests. Surface morphology was examined using confocal laser scanning microscopy and scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy (EDS) analyses were carried out to identify the composition of precipitates that could act as preferential sites for the onset of pitting corrosion. The results showed that the passive film presents n-type semiconductive behavior. Grain boundaries played an important role as pitting initiation sites for the AISI 409 stainless steel.

This study reports the high temperature erosion-oxidation (E-O) behavior of conventional and nanostructured Cr 3 C 2 -25(Ni-20Cr) coatings prepared by high velocity oxygen fuel (HVOF) spraying. As-received and nanostructured Cr 3 C 2 -25(Ni-20Cr) powders with mean crystallite sizes of 145 nm and 50 nm respectively, were used to prepare 120 -200 μm thick coatings on AISI 310 samples. The E-O behavior of the coatings prepared with the as-received (AR) and nanostructured (NS) powders was determined as weight change in a custom designed rig at room temperature, 450, 700 and 800 ºC. The Vickers microhardness, Young's Modulus and fracture toughness of the AR and NS coatings were determined, and the NS coatings exhibited higher values compared with the AR coatings. The E-O resistance of the NS coating was higher than that of AR coating at all temperatures, and particularly at 800 ºC. The increase in E-O resistance of the NS coatings is due to its superior mechanical properties as well as to the presence of some heterogeneities in the AR coatings. The E-O mechanisms of both types of the coatings are discussed, with special attention to that at high temperatures. The results suggest that at 800 ºC the E-O process is controlled by erosion of the oxide.

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