The influence of hydrogen on martensitic transformation of austenitic steels

Abstract

Abstract. The effect of hydrogen on the mechanical properties of the quenched and deformed specimens of Cr-Ni and Cr-Mn steels in 293...773 K temperature range has been investigated. Non-hydrogenated and hydrogenated (623 MPa H 2 ; 5 h) polished plane specimens with 3 6 20 mm working part were subjected to static tension with displacement rate of 0,1 mm/min in helium and hydrogen under 35 MPa pressure. It was established that all tested steels are sensitive to hydrogen degradation. The maximum effect of hydrogen has observed at room temperature, when decreased the elongation and reduction of area of specimens. Martensitic transformation of nitrogen-containing austenite (stable on air) was caused by hydrogen. In unstable steels hydrogen change the intensity of -transformation. Formation of polygonal dislocation substructure by preliminary mechanical or thermomechanical treatment decreases the hydrogen degradation of steels.The plastic and strength properties of unstable austenitic steels depend upon the intensity of the martensite transformation by deformation, which is controlled by alloying, mechanical working, and heat treatment [1,2]. Hydrogen has a significant influence on the processes of martensite formation and preliminary electrolytic or hightemperature hydrogen impregnation is accompanied both by a decrease and by the increase in the transformation temperature [3]. The role of deformation martensite in hydrogen embrittlement, especially in tests in a hydrogen medium, has been studied.The purpose of this work is an investigation of the features of the deformation martensite transformation and hydrogen embrittlement of 12Kh18N10T, 06Kh18N5G9AB and 07Kh13G20AN4 steels under various conditions of hydrogen action.Flat specimens with a cross section of 2 x 6 mm hardened from 1273°K where short-term tensile tested with a rate of 10 -4 sec -1 . A portion of the specimens was hydrogen-impregnated in advance in a working chamber with a hydrogen pressure of 35 MPa and a temperature of 623°K for 5 h. The temperature and time of impregnation were chosen so that the structure of the steels did not change during the hold. The original and hydrogenimpregnated specimens were tested both in hydrogen and in a neutral medium. For the purpose of revealing the rule of phase transformations in hydrogen embrittlement and also as the result of the fact that work hardening is frequently used for hardening unstable steels, a portion of the experiments was made on specimens deformed in air in advance at room temperature at a rate of tension of 10 -4 sec -1 . The phase composition of the steels was determined with the use of a DRON-3 diffractometer in copper Kradiation on 2 x 4 x 10 mm plates cut from the working portion of hardened or deformed specimens and also from the fracture zone of failed specimens. The integral intensities of the (111) and (110) lines were used for the quantitative calculations.It was established ( Figs. 1 and 2) that hydrogen has practically no influence on the short-term tensile strength in all conditions...

Hydrogen Cooling of Turbo Aggregates and the Problem of Rotor Shafts Materials Degradation Evaluation

“…Based on analyses of the existing data [167][168][169][170][171][172][173][174][175][176][177][178][179][180][181] and our own research, we propose a scheme of the "evolution" of the microstructure for 38KhN3MFA steel from which the TA rotor shaft was made which assumes that, during long-term operation, due to the complex action of factors-temperature increase and exposure to hydrogen-containing media-there is a change in the properties and parameters of the microstructure (Figure 8). It was recorded that there is a migration of complex carbides and VC carbides from the central part of the grain (Figure 8II) to the periphery and grain boundaries (Figure 8III).…”

Hydrogen-Assisted Aging Applied to Storage and Sealing Materials: A Comprehensive Review

“…Balitskii et al [61] conducted a laboratory test on two steel specimens, 05Kh12N23T3MR and 10Kh15N27T3B2MR, in a high-pressurized hydrogen environment and at elevated temperatures. A static tensional force was also applied to the temperature.…”

Influence of High Pressure and High Temperature Hydrogen on Fracture Toughness of Ni-Containing Steels and Alloys

“…It has been established [2,4] that, at some values of hydrogen pressure and strain rate, which depended on the chemical compositions and structures of materials, one obtains maximum influences of hydrogen on the plasticity, low-cycle fatigue life, and static and cyclic crack resistance of martensitic steels and nickel alloys. In short-term tension, austenitic dispersion-hardened steels are substantially embrittled by hydrogen after preliminary hydrogenation at elevated temperatures and upon attaining its content above 12 ppm, and the properties of hydrogenation specimens at room temperature in air and hydrogen are equal [1,2]. This is why we held a part of the specimens for 10 h in a hydrogen atmosphere under 623 K and 35 MPa.…”

“…It is known that age-hardened alloys are sensitive to hydrogen embrittlement [1][2][3][4]. Therefore, one of the most important requirements for such alloys is their resistance to hydrogen degradation.…”