Papers by Keyword: Hydrogen Absorption

Abstract: The use of duplex stainless steels (DSSs) is steadily increasing. For many uses where joining is needed, gas tungsten arc welding (GTAW) is one of the most important joining methods for DSSs. Since hydrogen embrittlement (HE) occasionally occurs in DSSs, understanding the relationship between the extent of HE and the welding condition is crucial to prevent HE. In this research, the effect of the heat input of GTAW process on the microstructure and the extent of HE in a UNS S31260 (JIS SUS329J4L) has been investigated. For this purpose, three samples have been prepared with diffrent velosity. All the samples have been cathodically hydrogen-charged, and then subjected to tensile test at a strain rate followed by fractography observation. Thermal desorption spectroscopy (TDS) has been carried out on the samples welded at low and average velosities. The results showed that tensile properties of the welded specimens were lower than those of base metal due to coarsening of the matrix ferrite grains and loss in the fraction balance of ferrite and austenite phases in the weld metal zone, where fracture took place.

Abstract: Abstract. Paper presents the results of the studies of the service properties of the 235JR and S355J2 low alloy steels subjected to the surface modification by friction-mechanical treatment, as tested in sea water simulated solution. The resistance of steels used in the marine vessels to the wear, cavitation erosion, general corrosion, corrosion cracking and hydrogen absorption has been examined. To evaluate the effect of the surface treatment, the comparative studies of the service properties of steels before and after treatment have been considered.

Abstract: The present paper aims at explanation of the advantageous role of partial substitution of iron by cobalt in Nd-Fe-B magnet for distinct inhibition of mechanically assisted corrosion phenomena. The hydrogen uptake by Nd₁₆Fe₇₆B₈ and Nd₁₆Fe₅₆Co₂₀B₈ sintered materials have been compared with the use of charge/discharge method in terms of the alloys corrosion behavior in strong alkaline solution. For initial cycles, the hydrogen discharge capacity of Co-containing alloy is 5-10 times lower than that for the Nd₁₆Fe₇₆B₈ reference alloy. After 6-7 cycles both alloys reveal comparable hydrogen capacity. Also the plots of polarization curves testify to comparable corrosion resistance for both materials. The unusual resistance of Nd₁₆Fe₅₆Co₂₀B₈ sinter to pulverization should be ascribed to strong inhibition of hydrogen absorption at initial steps of corrosion process.

Abstract: Cavitation attack in liquids generated a various states of stresses in surface layers of metals. Differences in stress state effects on hydrogen absorption activated by the cavitation implosion. Results of XRD investigation and FEM modeling shows on inhomogenity of process.

Abstract: The problem under consideration concerns the prevention of absorption of hydrogen in the processes of corrosion and electroplating of all industrially used metals with the aim of the modification of chemical and physical properties of base metal surface. Its properties change towards better brightness and soldering, minimal porosity and hydrophilicity of surface, increase of hardness and wear resistance. All these properties were evaluated by means of appropriate test equipment. Residual stresses in Cr coating by phase transformation, beginning in the electroplating process, acted in combination with absorbed huge quantity of hydrogen in intrinsic defects in the steel base. Internal stresses in the base/coating region resulted in severe deterioration of the durability of steel parts, as identified by static or sign-variable fatigue tests. The new stress-step technique makes possible an analysis of H content as a function of the depth in base metals and its distribution in coating metal .

Abstract: Multilayered SnO₂ hollow microspheres (MHS-SnO₂) have been successfully synthesized via a solvothermal method by using glycol-water as solvent. The morphology, composition and structure of the product have been characterized by field-emission scanning electron microscopy (FESEM) with an energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) and X-ray diffraction (XRD). The FESEM, TEM and HRTEM images indicate that the as-prepared microspheres show multilayered structure and the wall of the hollow microspheres is composed of single crystalline nanoparticles. Study on hydrogen absorption characteristics of MHS-SnO₂ performed at 373 K shows a good absorption capacity of 0.85 wt.%.

Abstract: With rising demands, oil and gas exploration of high-pressure high-temperature (HPHT) wells are increasing worldwide. Due to aggressiveness of HPHT environments, piping and equipments are constructed with high-strength corrosion resistant alloys (CRAs). Duplex stainless steel is one of the candidate alloys that offer high strength along with corrosion resistance. It possesses the advantages of both austenitic and ferritic stainless steels and hence, the name duplex or dual phase stainless steel. In order to control corrosion, cathodic protection is commonly being employed on the structures and equipment. Cathodic protection is accomplished by applying a direct current to the structure which causes the structure potential to change from the natural corrosion potential (E_corr). The required cathodic protection current is supplied by sacrificial anode materials or by an impressed current system. Hydrogen embrittlement (HE) is an associated phenomenon, which results in the production of hydrogen ions, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of metals and welds. To prevent this embrittlement, cathodic protection is closely studied in terms of finding the critical potential, pH, temperature etc. that does not cause hydrogen embrittlement. This paper describes the study carried out to find the role of pH on the absorption of hydrogen in Duplex Stainless steel. It has been observed that at a critical pH, hydrogen intake in the sample is very high, as compared to the pH below and above the critical pH. Critical pH observed for duplex stainless steel is a trade of between hydrogen evolution and absorption for given duplex structure.

Abstract: Synthesis of TiFebased metal hydride-forming alloy from mixed titanium iron oxide (ilmenite, FeTiO₃) was carried out by a two-stage reduction of the latter using H₂ and CaH₂ as reducing agents. The reversible hydrogen absorption capacity of the TiFe based material was about 0.5 wt. % H, that is significantly lower than the corresponding values (~1.8 wt. % H) reported in the literature. The main reason for that was in too high amount of oxygen present in the as-prepared TiFe alloy. Thus in order to improve the hydrogen absorption of the raw TiFe, the material was further alloyed together with Zr, Cr, Mn, Ni and Cu to yield an AB₂ alloy. For the as-prepared AB₂ alloy, the reversible hydrogen sorption capacity was about 1.3 wt. % H at P = 40 bar and >1.8 wt. % at P = 150 bar, which is acceptable for stationary applications. Finally, the material was found to be superior when compared to known AB₂-type alloys, with regard to their activation and poisoning tolerance.

Abstract: RNi₉In₂ and their hydrides crystallize in the YNi₉In₂ structure type. Low pressure hydrogenation leads to absorption of 1.5-3.4 H/f.u. RNi₉In₂ (R= Pr, Nd, Eu) as well as PrNi₉In₂H_1.7 and NdNi₉In₂H_1.5 exhibit Curie-Weiss behaviour in the 2-300 K temperature range. EuNi₉In₂ reveals ferromagnetism below approximately 40 K, which may be due to a secondary phase. Its hydride is Pauli paramagnet, indicating Eu³⁺ state. RNi₉In₂ (R= Pr, Nd) as well as PrNi₉In₂H_1.7 and NdNi₉In₂H_1.5 exhibit Curie-Weiss behaviour and lack of magnetic ordering down to T = 2 K.

Abstract: Microstructural changes and relaxation processes were examined in Fe-Zr based rapidly solidified samples. These phenomena occur far below crystallization temperature in the course of heat treatment, or even at room temperature, induced by absorbed hydrogen.