Hydrogen Resistance of Steels Alloyed with Nitrogen

We study the resistance of stainless steels with different contents of nitrogen after plasma-arc remelting to hydrogen degradation. The dependence of the mechanical properties of steels on the content of nitrogen is quite complicated, which is explained by changes in the phase composition. In the analyzed collection of steels (Kh18AN9, Kh20AN15, Kh18AG10, and Kh18AG15), Kh18AG15 steel has the best combination of the characteristics of strength and plasticity in hydrogen.     

Development of an austenitic chromium-manganese steel with high hydrogen resistance

We compare the results of studying the effect of hydrogen on the characteristics of short-time strength and low-cycle durability of austenitic stainless steels and age-hardening alloys. We show that austenitic stainless 06Kh20N16G6AF steel with solid-solution strengthening and the optimal content of nickel, manganese, and nitrogen possesses high mechanical characteristics and is least inclined to hydrogen degradation. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 5, pp. 95–100, September–October, 2005.     

A method for the prevention of premature failures of power plants using hydrogen as the working medium

Qe analyze failures of power-generating units working on liquid hydrogen caused by the most dangerous type of embrittlement—reversible hydrogen embrittlement of the metal. We consider the existing methods for the protection of various structural elements against hydrogen embrittlement and discuss their advantages and shortcomings. A method for the protection of difficultly accessible internal hollows of power-generating units against hydrogen embrittlement by introducing active gaseous admixtures in the working volume is described in detail. The mechanism of action of these admixtures is analyzed refractory alloy as examples, we demonstrate the positive effect of admixtures to gaseous hydrogen under a pressure of 35 MPa. The proposed method enables one, in some cases, to use hydrogen (as a new ecologically pure fuel) without serious changes in the structure of the unit and in the technological process. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 4, pp. 53–56, July–August, 1998     

Effect of Hydrogen on the Mechanical Properties of Welded Joints of 03Kh12N10MT Steel and KhN55MBYu Alloy

We have studied the hydrogen degradation of welded joints of 03Kh12N10MT steel and KhN55MBYu alloy, used in the aerospace industry. We have established that the highest level of strength, plasticity, and low-cycle durability in gaseous hydrogen under a pressure of 35 MPa is provided by argon-arc welding for joining homogeneous materials and by electron-beam welding for dissimilar materials.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 6, pp. 55–61, November–December, 2004.     

Enhancement of the durability of structural steels and their welded joints by plastic deformation

Conclusions The fatigue and corrosion-fatigue resistance of low-alloy steels increases as degree of plastic prestraining increases to 29%. The resistance of the 08kp steel prestrained and hardened by surface plastic deformation and its welded joints to fatigue and corrosion-fatigue fracture is higher than for the 08GSYuT alloyed steel. The procedures of pneumatic shot blasting and shot blasting prove to be efficient methods for increasing the cyclic and low-cycle durability of welded joints both in air and corrosive media. The corrosive medium considerably decreases the low-cycle durability of welded joints of sheet steels. The effect of the medium is more pronounced for alloyed steels and becomes weaker as the amplitude of strains increases. Translated from Fizyko-Khimichna Mekhanika Materially, Vol. 36, No. 3, pp. 121–122. May-June, 2000.     

Degradation of steel in gaseous hydrogen with inhibiting admixtures

We have investigated the possibility to protect metal constructional elements of power-generating equipment against hydrogen embrittlement by introducing O₂ and CO + H₂ O admixtures into the working volume. We have shown their positive influence on the mechanical properties of 03Kh12N10MT steel and KhN60K16MBYu alloy under short-term and long-term static tension within the temperature range 293–1073 K in gaseous hydrogen with a pressure of 35 MPa. However, we have not detected an inhibiting effect of the admixtures mentioned above in the case of preliminary high-temperature hydrogenation of unloaded smooth and notched specimens made of 05KhN23MTR steel and KhN60K16MBYu alloy. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 3, pp. 71–75, May–June, 2007.     

Prediction of the contact durability of back-up rolls of forge-rolling mills in the process of development of pitting

We construct an algorithm for calculating the residual life of the near-surface layer of back-up rolls of rolling mills according to the development of pitting. Within the framework of the numerical-analytical two-stage model of evaluating the contact durability of rolling solids of revolution under conditions of boundary friction (lubrication) proposed earlier, we construct and analyze the trajectories of propagation of edge cracks at the shear and rupture stages. A criterion of transition between these mechanisms is proposed. Furthermore, we evaluate the durability of rolls with the help of characteristics of the cyclic crack resistance of 9KhF, GH, and SKH roll steels. Using disk specimens made of 9KhS roll steel, we study the dependence of contact durability on the friction coefficient between the rolling solids of revolution, the size of contact area, contact pressure, the slope of the initial shear crack, etc. Finally, we compare the results of theoretical and experimental investigations. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 6, pp. 95–105, November–December, 2006.     

Problems of Hydrogen Degradation of Metals

We present a new scientific trend concerned with the behavior of materials interacting with hydrogen, namely, hydrogen-containing materials science. Most of the attention is concentrated on hydrogen degradation of structural materials, which is a major aspect of this trend, and the types of hydrogen degradation are considered. The most important factors predetermining the processes observed are the tendency of hydrogen to localization in the metal and a decrease in the binding forces between atoms of metal. Tasks aimed at solving the problems of hydrogen degradation of metals are formulated.     

Temperature dependences of the mechanical properties of austenitic and martensitic steels in hydrogen

The influence of gaseous and preliminarily dissolved hydrogen on the characteristics of short-term static strength, crack resistance, and low-cycle durability of martensitic and austenitic steels is studied within the temperatures range 293–1073°K, under pressures of hydrogen varying within the range 0–35 MPa, for the strain rates of 0.01–100 mm/min, and the strain amplitudes of 0.8–1.6%. We determine the loading rates and the conditions of action of hydrogen leading the maximum possible hydrogen degradation of each material. The influence of the chemical composition and structural state on the degree of embrittlement and fractographic features of the fracture of steels in the presence of hydrogen is analyzed. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 5, pp. 53–64, September–October, 2007.