V. B. Vykhodets

Effect of strengthening friction treatment on the chemical composition, structure, and tribological properties of a high-carbon steel

The structure and chemical composition of nanocrystalline layers formed on the surface of a steel U8 with 0.83 wt % C (quenched, as well as quenched and tempered at 200°C) under the conditions of frictional loading by a hard-alloy indenter in different media (gaseous and liquid nitrogen, air) have been investigated by the methods of transmission electron microscopy, X-ray diffraction analysis, nuclear reactions, Rutherford back scattering, and wave- and energy-dispersive microanalyses. Maximum levels of defectiveness (high density of dislocations and point defects) and microhardness of the nanocrystalline structure have been attained upon friction treatment of the low-temperature tempered steel in a liquid-nitrogen medium because of deformation localization in a thin surface layer, intensification of deformation-induced dissolution of the ɛ carbide phase, and saturation of the layer with nitrogen and oxygen atoms, the latter dissolved in the liquid nitrogen as an impurity. A comparative analysis of the in-depth distribution of microhardness in frictionally strengthened surface layers has been performed for the steel with initial structures of tetragonal (untempered) and low-tempered (tempered at 200°C) martensite. A markedly larger depth of strain hardening has been attained upon friction treatment in the quenched untempered steel due to effective development of deformation-induced dynamic aging of high-carbon martensite even at small deformations. It has been established that the strengthening upon deformation of the surface by a sliding indenter exerts a positive influence on the tribological properties (wear rate and friction coefficient) of the steel under the conditions of frictional heating of different intensity.

Structure evolution of pure iron upon low-temperature deformation under high pressure

Structure evolution of iron (99.97% purity) deformed by shear under pressure at 80 K in a medium of liquid nitrogen has been investigated. It has been found that, along with dislocation slip, twinning and development of deformation microbands become operative mechanisms of low-temperature deformation. This led to specific type of inhomogeneity of the structure in which, up to ultimately attained degrees of deformation, low-angle misorientations are retained and, unlike room-temperature deformation, no homogeneous submicrocrystalline (SMC) structure is formed. Twinning contributes to the refinement of structure elements that are more than 1 μm in size; the further refinement occurs by the dislocation-disclination mechanism and goes to the steady-state stage.

H/D isotope effect for solubility of hydrogen in doped perovskites

A novel method for studying the H/D isotope separation effect in the “nonstoichiometric oxide-gas” system is suggested. The theoretical scheme of this method is represented for doped perovskites of the ABO3 family, but this approach is also applicable to other compounds where the solubility of hydrogen is determined by the content of oxygen vacancies. The suggested approach is used to determine the H/D isotope effect in hydrogen solubility from the experimental data for proton-conducting oxides. The measurements have been taken using the nuclear microanalysis of fine-grain BaZr0.9Y0.1O3 − y powders. The method is based on the study of the products of the 2H(d, p)3H nuclear reaction. The observed pronounced isotope effect is in quantitative agreement with our theoretical predictions.

The trapping of hydrogen ions in vanadium and titanium

Abstract The accumulation of implanted deuterium has been investigated at room temperature in vanadium, titanium and their alloys up to (2–15) × 1017 ions cm−2 fluences by means of D(d, p)T reaction. The amount of accumulated D was measured using a 700 KeV D+ ion beam during implantation. It is found that concentration of implanted deuterium in irradiated samples nonmonotonously increases the increasing fluence and in a complicated manner depends upon Vue5f8Ti alloy composition. These data are explained by concentration dependence of D diffusion coefficient in Vue5f8Ti alloys, structural ion irradiation induced inhomogeneity of alloys with > 5–8 at.% Ti, and irradiation-enhanced diffusion of deuterium.

Modification of amorphous diamond-like films by bombardment with low-energy ions☆

Abstract The study is concerned with the influence that bombardment with low-energy (approximately 1 keV) ions of argon, oxygen, nitrogen or hydrogen exerts on properties of the amorphous diamond-like coatings (DLCs) produced by vacuum pulse sputtering of graphite in an arc discharge. It is shown that hydrogen treatment leads to the formation of C:H films whose composition depends on specific bombardment conditions. Bombardment with the other ions results in etching and smoothing of the DLC relief, while the film composition remains unchanged. Ionic bombardment increases the share of the diamond-like component in the film structure.

Practical use of strength and anticorrosion properties of amorphous carbon thin films

Abstract A study was made of the protective properties of amorphous C thin films deposited by the method of pulse sputtering of graphite on substrates having a temperature of approximately 175°C. It is shown that the films can be successfully used to improve the service properties of audio or video heads and surgical cutting instruments.

Grain boundary self-diffusion of tracer 18O atoms in nanocrystalline oxide LaMnO3 + δ

Diffusion coefficients of tracer 18O atoms at boundaries of nanograins of LaMnO3 + δ oxide have been measured in the temperature range of 400–500°C. The samples of the nanocrystalline oxide are prepared with the use of the shockwave loading method. The concentration profile of the tracer atoms after diffusion annealing is measured with the use of the nuclear microanalysis method. The activation energies of the grain boundary diffusion amounts to about 2 eV and the boundary width is ∼0.05 nm. The measured coefficients of the grain boundary diffusion at 500°C exceed the corresponding coefficients of the volume diffusion by seven orders of magnitude.

Studying distribution of gaseous impurities and carbon in titanium alloys using nuclear microanalysis

The mechanism of the formation and modification of macrodefects containing atoms of light elements upon melting and thermal and mechanical treatment of titanium alloys has been studied. To this end, an approach based on the investigation of the concentration distribution of oxygen, nitrogen, and carbon in the zone of a macrodefect using nuclear microanalysis with a locality of measurements over the sample surface to about 90 μm has been used. It has been established that a decrease in the concentration of carbon in tungstencarbide-based macrodefects upon alloy melting occurs according to the diffusion mechanism. The same mechanism is characteristic of the process of dissolution of defects of deformation origin, such as titanium oxynitrides, upon solid-state heat treatment.

Diffusion of Insoluble Carbon in Zirconium Oxides

The diffusion coefficient of insoluble carbon in zirconium oxides has been obtained for the temperature range of 900–1000°C. There are no published data on the diffusion of insoluble impurities; these data are of current interest for the diffusion theory and nuclear technologies. Tracer atoms 13C have been introduced into oxides by means of ion implantation and the kinetics of their emission from the samples in the process of annealing in air has been analyzed. The measurements have been performed using the methods of nuclear microanalysis and X-ray photoelectron spectroscopy. The diffusion activation energy is 2.7 eV and the carbon diffusion coefficient is about six orders of magnitude smaller than that for oxygen self-diffusion in the same systems. This result indicates the strong anomaly of the diffusion properties of carbon in oxides. As a result, zirconium oxides cannot be used in some nuclear technologies, in particular, as a material of sources for accelerators of short-lived carbon isotopes.

RADIATION-INDUCED SEGREGATION OF DEUTERIUM IN AUSTENITIC STEELS AND VANADIUM ALLOYS

Abstract The accumulation and distribution of implanted deuterium were studied through simultaneous analysis using the nuclear reaction D(d,p)T for some austenitic, austenitic–martensitic steels, Fe–16% Cr, V–4% Ti–4% Cr, V–10% Ti–5% Cr alloys, and vanadium. The implantation was carried out by 700-keV deuteron irradiation at room temperature with a total implantation dose of about 2xa0×xa010 18 cm −2 . It is shown that the deuterium segregation induced by ion irradiation in vanadium and the Fe–16% Cr alloy remained unchanged during room temperature holding after implantation. On the other hand, in the two-phase steel and the V–Ti(–Cr) alloys the holding led to a partial elimination of the concentration inhomogeneity of the implant in the irradiated portion, while in the austenitic steel deuterium segregation increased probably due to the migration of deuterium from the unirradiated volume to the irradiation zone. Possible reasons for different behavior of the implanted deuterium in different materials will be briefly discussed.