The geopolymer although being a recently discovered material, it is already present in many industrial sectors. This range of applications is due to the commitment of the scientific community to understand and manipulate the material, seeking a contribution in this regard, it has produced geopolymer matrix composites with quasicrystalline and reinforcement, Al62,2Cu25,5Fe12,3 in the proportion of 10%, 20% and 30% by volume. These composites were obtained by manual production and heat treated at 400 º C for two hours. The characterization was made with the aid of scanning electron microscopy (SEM) and x-ray diffraction (XRD). Diffractograms of composites without heat treatment showed characteristic peaks of the phases present in the matrix and reinforcement. For the composites with heat-treated, it was observed that besides the phases mentioned above the presence of diffraction peaks possibly associated phase silica sodium aluminate. The composite showed good interface quasicrystal / geopolymer, showing the existence of a phase with lamellar morphology in the treated material.
The formation of brittle microstructures around the fusion line in dissimilar welds has required a deeper microstructural analysis in this region. The study becomes more relevant when these welds are used in environments that facilitate hydrogen embrittlement. The present work aims to characterize the microstructure and hardness at the diluted zone interface in joints welded with dissimilar materials. Aiming for a better efficacy in the microstructural characterization of this zone, samples of both normal cross-section (NCS) and section with slope were used, according to the low-angle microsectioning (LAMS) technique, which allows a greater amplification of partially mixed zones (PMZs). The results indicated the diffusion of carbon from the heat-affected zone (HAZ) towards the fusion line which, in combination with other alloying elements, form highly brittle carbides. In turn, the hardness of the base metal and the HAZ was reduced after post weld heat treatment, whereas in the weld metal an opposite behavior was observed. The dissimilar interface was promising for applications in environments facilitating hydrogen embrittlement, especially regarding the characteristics of zone Φ.
A 182 F22 steel, used in components subsea for oil extraction, are previously buttered with ductile metal such as Inconel 625, before being welded to steel pipes similar to ASTM A36 steels. The thermal buttering weld cycle provides the formation of high hardness micro-phases and carbides at the interface between F22 steel and the buttering with Inconel, which when in contact with hydrogen, originating from the cathodic protection applied to these equipment, can lead to the embrittlement of this region, causing fragile fractures. In this work, ASTM A 182 F22 steel, buttered with Inconel 625 and welded to A36 steel, submitted to post-weld heat treatment without hydrogenation and subjected to cathodic protection for hydrogen permeation were submitted to fracture toughness test. The welds and buttering were done using GMAW process with AWS ERNiCrMo-3 wire as filler and buttering metal and a mixture of Ar and He as shield gas. The results indicated a 56% of area reduction, and 15% in the elongation values in the tensile tests, in addition to a 13.3% reduction in the CTOD value, for welded joints subjected to hydrogen permeation, which showed a quasi-cleavage fracture mechanism.
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