The Effect of Electrolytic Hydrogenation on Mechanical Properties of T92 Steel Weldments under Different PWHT Conditions

In the present work, the effects of electrolytic hydrogen charging of T92 steel weldments on their room-temperature tensile properties were investigated. Two circumferential weldments between the T92 grade tubes were produced by gas tungsten arc welding using the matching Thermanit MTS 616 filler material. The produced weldments were individually subjected to considerably differing post-welding heat treatment (PWHT) procedures. The first-produced weldment was conventionally tempered (i.e., short-term annealed below the Ac1 critical transformation temperature of the T92 steel), whereas the second one was subjected to its full renormalization (i.e., appropriate reaustenitization well above the T92 steel Ac3 critical transformation temperature and subsequent air cooling), followed by its conventional subcritical tempering. From both weldments, cylindrical tensile specimens of cross-weld configuration were machined. The room-temperature tensile tests were performed for the individual welds’ PWHT states in both hydrogen-free and electrolytically hydrogen-charged conditions. The results indicated higher hydrogen embrittlement susceptibility for the renormalized-and-tempered weldments, compared to the conventionally tempered ones. The obtained findings were correlated with performed microstructural and fractographic observations.

Effect of Hydrogen Redistribution during Aging on the Martensitic Transformation and Superelasticity of Nanocrystalline TiNi Alloy

The paper presents the results of a study the hydrogen effect on the structural-phase transformations and the superelasticity in binary ultrafine-grained (UFG) TiNi based alloy after diffusion redistribution hydrogen as a result of aging at room temperature. The redistribution of hydrogen in the process of long-term aging after electrolytic hydrogenation of UFG wire specimens the Ti49,1Ni50,9(at.%) stabilizes the B2 structure. Superelasticity in samples aged at room temperature after hydrogenation is significantly deteriorated.

Analysis of Plastic Flow Localization in Bimetal Electrolytically Saturated with Hydrogen

Plastic deformation of bimetal compound of austenitic stainless and low-carbon construction steels, resistant to corrosion, is localized through the digital image correlation method upon the uniaxial tension of sample. The evolution of zones of plastic deformation in bimetal is inspected upon the onset of the process and is exposed to hydrogen saturation in a three-electrode electrochemical cell at a controlled constant cathode potential for 6 hours. Localized plastic deformation zones are found to form and evolve during the tension of bimetal samples both at the onset and after 6 hour of the electrolytic hydrogenation throughout the plastic yielding in the primary, protective and transitional layers of the bimetal. The bimetal fracture is initiated by stress concentrated in the bimetal transition layer. Nucleation and propagation of a crack is observed at early work-hardening stages. The fracture of bimetal after hydrogenation is established to be more ductile as compared with precursor.

CHANGES IN ULTRASONIC VELOCITY AT HYDROGEN EMBRITTLEMENT OF HIGH-CHROMIUM STEEL

The paper presents research into changes in the ultrasonic velocity (Rayleigh wave propagation) at plastic deformation of the type 40Kh13 corrosion-resistant high-chromium steel with a sorbitol structure after high-temperature tempering (original state) and after electrolytic hydrogenation saturation for 12 and 24 h. The method implementation for measuring Rayleigh wave propagation includes a periodic generation of square-waves 100 nm long. Measurements are performed at the input of a radiating piezoelectric transducer including the wave propagation over the specimen using a receiving piezoelectric transducer connected to a digital oscilloscope. Measurements show changes not only in the deformation curve at uniaxial tension but also in the dependence between the ultrasonic velocity and deformation.

Study of Plastic Flow of Aluminum Alloy Using Digital Speckle Photography

The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.