Hydrogen Effect on Cumulation of Failure, Mechanical Properties, and Fracture Toughness of Ni-Cr Alloys

Abstract

Influence of hydrogen pressure and internal hydrogen contents on short-term strength, plasticity, and plane-stress fracture toughness of 05Cr19Ni55 alloys at pressure up to 30 MPa was investigated. It was established that the crack resistance parameters K c of alloys decrease with displacement rates decreasing similar to elongation (δ) and reduction of area (ψ) of smooth specimens. e maximum hydrogen influence is achieved at strain rate speeds less than 0.1 mm/min and hydrogen pressures above 15 MPa when δ and K c of prehydrogenated samples are reduced by 3 times. e plane-strain conditions required for the evaluation of K _c were fulfilled on compact tension 05Cr19Ni55 alloy specimens with thickness above 20 mm under hydrogen pressure 30 MPa and preliminary dissolved hydrogen concentration above 20 wppm. Regardless of the test conditions, the value of the characteristics of plasticity (δ, ψ) and fracture toughness (K s ) of alloy (TO1) specimens oriented in the transverse direction (orientation TV) is significantly lower than that of specimens oriented in the longitudinal direction (LT). Alloy cleaning by vacuum arc remelting and optimization of heat treatment regime increase their hydrogen resistance.

Prediction carbides composition in nickel-based superalloys directional crystallization

“…It is known [1,7,8] that MC carbides are formed in the process of crystallization (solidification) in the form of discrete particles in the intergrain and intragranular space, as well as in the interdendritic regions. Carbides of the MC type are formed in a liquid due to strong segregation of carbon, when its amount is higher than 0.05 %, as well as at temperatures slightly below the solidification temperature of the alloy.…”

Hydrogen and Corrosion Resistance of Nickel Superalloys for Gas Turbines, Engines Cooled Blades

“…It is known that the sensitivity to hydrogen and the number of areas of intergranular fracture in heat-resistant nickel alloy samples decrease with decreasing grain size, even though the hydrogen concentration in coarse-grained samples is lower than in finegrained ones [35,. As in the case of deformable alloys [38][39][40][41][42], the degree of hydrogen embrittlement of cast alloys depends on their chemical composition and heat treatment regimes, which determine the features of the material structure [29,36].…”

“…The CM88Y alloy with higher strength is significantly embrittled at 800 • C and is sensitive to the action of hydrogen even at 900 • C (Figures 5 and 6). It has been established that increasing the hydrogen durability (HD) of austenitic iron-nickel steels and alloys is achieved by forming a structure with thin grain boundaries with increased cohesive energy by introducing boron, lanthanum, and zirconium, by optimizing the morphology of intermetallic [35,[39][40][41][42]. Therefore, the ZhS3DK alloy, in which there are none of these alloying elements, is much more embrittled by hydrogen in the temperature range of 20-700 • C. At higher temperatures, its strength decreases sharply, and the effect of hydrogen weakens (Figure 6).…”

Improvement of the Mechanical Characteristics, Hydrogen Crack Resistance and Durability of Turbine Rotor Steels Welded Joints

“…Even the simulation of the soldering regime with the short-term (15 min) heating of KhN43MBTYu and 05Cr19Ni55 alloys to 1473 K leads to an increase in grain size and the concentration of large grain boundary Uneven grain sizes, the sizes and distribution of reinforcing phases, local thermal stresses and other defects cause the significant sensitivity of various structural elements of welded joints to the action of hydrogen [41][42][43][44][45][46]. Even the simulation of the soldering regime with the short-term (15 min) heating of KhN43MBTYu and 05Cr19Ni55 alloys to 1473 K leads to an increase in grain size and the concentration of large grain boundary intermetallic precipitates, which significantly enhances the hydrogen embrittlement of materials [47,48]. In the presence of hydrogen, the mechanical characteristics of welded joints deteriorateshort-term strength and ductility [43,44] and low-cycle durability [44,45].…”

“…Important characteristics of critical structures, including steam and hydrogen turbine rotors, are the parameters of crack resistance , which are also significantly reduced by hydrogen [41,42,[46][47][48][53][54][55][56] with a pressure up to 10 MPa. Given the variety of factors that determine the properties of welded elements in hydrogen-containing environments, to assess their performance requires the experimental determination of a set of physical and mechanical properties of a particular joint [119][120][121][122][123][124][125], especially for the structural elements of the hydrogen energy buffer (electrolizers, fuel cells, hydrogen storage and grid distribution), with the intention of utilizing hydrogen and the accompanied phenomenon of their hydrogen degradation during long-term service.…”