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 Kc of alloys decrease with displacement rates decreasing similar to elongation (δ) and reduction of area (ψ) of smooth specimens. The maximum hydrogen influence is achieved at strain rate speeds less than 0.1 mm/min and hydrogen pressures above 15 MPa when δ and Kc of prehydrogenated samples are reduced by 3 times. The plane-strain conditions required for the evaluation of KІc 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 (Kс) 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.
Highlights
Heat-resistant nickel alloys are widely used in energy and aerospace engineering in contact with high-pressure hydrogen-containing gas mixtures [1,2,3,4,5]. erefore, one of the most important requirements for such alloys is their resistance to hydrogen degradation
In order to ensure an adequate level of safety and optimal durability of such structural elements, experimental tests in gaseous hydrogen are required to determine the effect of various factors
By the fracture mechanics approaches, evaluation of static load durability of structures and critical crack size in technological or operational circumstances have been calculated as the values of critical stress intensity factor KIc (Kc) [1, 3,4,5,6]. Use of this option to evaluate workability details in gaseous hydrogen is limited to a number of factors caused by the methodological aspects of the determination in laboratory conditions and characteristics of initiation and growth of cracks in the presence of hydrogen [3,4,5,6,7,8,9]. e materials employed in hydrogen energy should have little sensitivity to cracks and cuts that have a high ability to relax tension in the areas of highest concentration, which does not archive the plane-strain state for research specimens and determines KIc by standard methods in air [5,6,7,8]. erefore, most studies of the impact of hydrogen on mechanical behavior of structural steels and alloys were carried out with tests on short-term static tensile and low-cycle durability [1,2,3, 10, 11]. e
Summary
Heat-resistant nickel alloys are widely used in energy and aerospace engineering in contact with high-pressure hydrogen-containing gas mixtures [1,2,3,4,5]. erefore, one of the most important requirements for such alloys is their resistance to hydrogen degradation. By the fracture mechanics approaches, evaluation of static load durability of structures and critical crack (defect) size in technological or operational circumstances have been calculated as the values of critical stress intensity factor KIc (Kc) [1, 3,4,5,6]. We study the influence of high-pressure gaseous hydrogen on short-term strength, plasticity, and static crack resistance of a nickel-based alloy 05Cr19Ni55 with different modes of heat treatment and chemical composition variations.
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