A complex modification of 25CrMoV steel has been carried out, which includes nitriding in arc-enhanced glow discharge plasma, deposition of metallic sublayer (Mo, Cr or Ti) and deposition of top layer of Mo2N coating. The structure studies showed that depending on the material and the thickness of the sublayer (1.5...6 µm), defects and delaminations could form at the interfaces, while no defects were observed in the absence of the metallic sublayer. The concentration of nitrogen in the complex modified layers depends on the composition of the metallic sublayer, but does not affect the total depth of nitriding of the hardened steel ~ 160 µm. The hardness of the nitrided layer is ~ 12 GPa, and the hardness of the Mo2N coating is ~ 30 GPa. The cavitation resistance of complex-modified 25CrMoV steel without the metal sublayer is 2 times higher than the initial steel.

The microstructure, hardness and cavitation wear of T91 ferritic-martensitic steel are studied and compared with some other reactor steels of the Eurofer 97 and Cr18Ni10Ti grades. It is shown that the cavitation resistance of T91 steel is 34 times higher than the cavitation resistance of Eurofer 97 steel and 11 times higher than the resistance of traditionally used Cr18Ni10Ti austenitic steel. Unlike the Eurofer 97 ferritic-martensitic steel alloyed with tungsten and tantalum, the T91 steel alloyed with molybdenum and niobium has larger prior austenite grain sizes (20 vs. 6 μm), length and width of martensitic packets (30–40 and 3–10 vs. 10–20 and 2–4 μm, respectively), and microhardness (2.47 vs. 2.07 GPa).

The wear rate of titanium alloys VT1-0, TC5, VT6, VT14, OT4 under the action of microshocks due to cavitation, which is created in distilled water under the surface of the ultrasonic wave emitter, were determined. It was found that the increase in hardness and improvement of cavitation wear resistancefor these alloys depends on the alloying elements, and is also increased after heat treatment and ion-plasma modification of the sample surface. Although no unambiguous correlation was found between the structural class of the alloys and their cavitation wear. Due to ion-plasma modification of alloys, the cavitation wear resistanceis increased by several times, in particular, the VT6 alloy by 3 times. The phase composition of the samples before and after ion-plasma modification was studied and it was found that alloy resistance to cavitation significantly depends on it.

Introduction. 15Kh12VNMI: and 20Kh1M1F1TR steels are used in mechanical engineering as a material for turbine parts. To increase the operating temperature of such parts, it is necessary to improve the heat resistance of their surface. Problem Statement. Increasing the heat resistance of steel surface is possible by applying a protective layer to it. It is almost impossible to say unequivocally which coating and method of its formation on a particular steel provide a sufficient increase in the heat resistance of the surface of this material. Previously, 15Kh12VNMF and 20Kh1M1F1TR steels were not protected by vacuum chromium plating in sodium chloride vapor. Purpose. The purpose of this research is to study the process of vacuum activated chromium plating of 15Kh12VNMF and 20Kh1M1F1TR steels and its effect on the characteristics of the samples made of these materials. Materials and Methods. The samples for research are made of 15Kh12VNMF and 20Kh1M1F1TR steels. Tests for cavitation and abrasive wear have been made on stands. The heat resistance test has been carried out in a muffle furnace in the air. The metallographic methods and X-ray fluorescence analysis (XRF) have been used to study the sample surface. Results. The 15Kh12VNMF and 20Kh1M1F1TP steel samples have been plated with chromium by the vacuum saturation method in sodium chloride vapor at temperature T = 1070 degrees C and 1100 degrees C; the process duration is 4 and 10 hours. It has been found that the samples made of these steels and plated with chromium under cavitation and abrasive action slightly fall behind the original samples in terms of wear resistance. It has been established that wizen the samples are chromium plated, a diffusion layer with a thickness from 50 to 1.30 pm is fonned on their surface, depending on the treatment conditions. The content of chromium in the surface layer of 15Kh12VNMF and 20Kh1M1F1TR steels varies, respectively, within 56-56 wt. % and 81-8 1 wt. %, depending on the saturation process parameters. The comparative tests of these samples for heat resistance have been carried out in the air, at a temperature of 900 degrees C. It has been found that the heat resistance of chrome-plated samples is much higher than that of the original ones. Conclusions. The studies of the process of vacuum activated chromium plating of samples made of 15Kh12VNMF and 20Kh1M1F1TR steels have shown that such treatment significantly increases the heat resistance of these materials in comparison with the original ones.

In this work, we studied the properties of samples from steel 15Cr12WNiMoV after vacuum activated chromium plating at temperatures of 1070 and 1100 °C for 4 and 10 h. It was found that after chemical-thermal treatment on the samples a diffusion layer with a thickness of 50 to 130 µm is formed, consisting of 56…82 wt.% of chromium, the rest is iron. Metallographic studies were carried out on the samples and tests for heat resistance were carried out at a temperature of T = 900 °C. It was found that chrome-plated samples significantly exceed the initial samples and nitrided ones in terms of heat resistance. Tests of samples for tensile strength after chromium plating showed a significant increase in strength indicators for ultimate strength and yield strength. The plasticity characteristics of these samples are reduced.

Protective coatings with different compositions of Fe, Cr, and Al were deposited by cathodic arc evaporation method on fragments of Zr1Nb alloy fuel claddings. The influence of the composition and structural state of the developed coatings on their physical and mechanical properties (microhardness, resistance to corrosion and cavitation and abrasive wear) has been studied. It is shown that the optimal combination of mechanical properties and high resistance to oxidation from a series of studied coatings FeCr, FeCrAl, and CrAl have coatings of the FeCrAl system with a concentration of Cr ~ 22 at.% and Al ~ 14.3 at.%. It was found that protective coatings such as FeCr, FeCrAl, and CrAl with a thickness of ~ 12 μm significantly increase the resistance to oxidation and prevent the destruction of fuel claddings under oxidation in air at a temperature of 1150 °C for 1 h.

The process of vacuum-arc deposition of protective coatings from multicomponent FeCrAl cathodes and 18Cr10NiT stainless steel onto fragments of Zr1Nb alloy claddings has been developed. The influence of the reaction atmosphere (vacuum, nitrogen, oxygen) during the deposition of coatings on their structure, mechanical and corrosion properties is investigated. Coatings deposited in vacuum from the Cr18Ni10T cathode have the best set of mechanical properties and corrosion resistance; whereas coatings based on FeCrAl require composition optimization. It has been established that coatings deposited from FeCrAl and stainless steel cathodes with a thickness of 20 μm significantly increase oxidation resistance and prevent the destruction of fuel cladding under exposure to air at 1150 °C for 1 h.

In the work, the surface of samples made of 25X1MF steel was saturated with chromium. For this, the method of vacuum activated diffusion chromium plating was used. In this process, sodium chloride was used as an activator. It was found that vacuum activated diffusion chromium plating of samples made of 25Kh1MF steel leads to the formation of a surface layer containing from 87 to 97 wt.% of this element. It was found that an increase in the temperature of the process and its duration leads to an increase in the chromium content on the surface of the samples. The tests showed that in the case of cavitations-erosion effects on the surface of chrome-plated samples of steel 25X1MF they have higher resistance. With abrasive wear, the resistance of the chrome-plated steel surface is 1.8 to 3 times higher compared to untreated material.

Fe-Cr-Al alloys are considered as one of the possible replacement of zirconium alloys for nuclear fuel claddings. The microstructure, phase composition, oxidation resistance, mechanical properties and cavitation resistance of one commercial and four experimental Fe-Cr-Al alloys doped with yttrium, molybdenum and zirconium are studied in this work. All alloys under study have the BCC phase as the main. Alloying with similar to 2 % of zirconium results in the formation of microstructure consisting of the matrix phase grains and intergranular eutectic: BCC matrix phase + FCC Laves phase ZrFe2. The highest resistance to oxidation in air at temperature of 1300 degrees C is observed in the alloy doped with yttrium and molybdenum. Microhardness, nanohardness and yield strength have close values for all alloys except for the Zr-doped alloy which has significantly higher values of these parameters. The Fe-Cr-Al alloy doped by Y, Mo and Zr is the most cavitation resistant one.

The paper presents the results of the study on the influence of a high substrate bias voltage from 300 up to 1300 V on the titanium nitride coating deposition under nitrogen pressure of 2 Pa. The deposition rate, phase and chemical composition, adhesion and mechanical properties of coatings, macroparticle number and size distribution were investigated.

This paper presents the data obtained on the density, microhardness, structure, erosion damage of surface layers of Mo and W monocrystals, of amorphous Zr-based and W-based alloys subjected to the cavitation erosion and sputtering with argon ions. The dependence of the erosion rates of samples on their microhardness H-mu has been established. It was found that in the range of H-mu from 1.5 to 6...7 GPa, the erosion rates are changing for both types of loading in a similar way proportional to H-mu(-n), where for the cavitation effect n congruent to 3.6. The minimum values of erosion rates are referred to amorphous alloys. For samples with H-mu > 7 GPa, the erosion rates are increasing as the ductility of materials decreases.

At the NSC KIPT and PJSC "Turboatom" test rigs the investigations were carried out to measure the 15Khl1MV blade steel sample erosion caused by the cavitation action and water drop impact. The test samples were materials in as-received condition, as well as, after ultrasonic machining, rolling, hardening, hardening + ultrasonic machining, nitriding, high-frequency current (HFC) hardening. (HFC) + coating deposition. It has been found that depending on the surface layer hardening method, the sample erosion rate decreases from 1.7 to 5 times as compared to the erosion rate of as-received material samples. It is shown that hardened TiNi, W3Co, WR27 alloys have about 1.7-5 times higher erosion resistance as compared to the same samples in as-received condition.

It is shown, that small silicon admixtures (to 3 %) in coatings on the basis of titanium nitrides lead to the considerable changes of performances (resistance against the wear and the ion sputtering, erosion resistance, a roughness) of deposited condensates in comparison with coatings on the basis of "pure" titanium nitrides. So, with growth of concentration of silicon in the coatings, the resistance against the wear and the ion sputtering raises, and resistance against cavitation decreases. Presence of essential interior stresses in the coatings synthesised in the field of pressures of nitrogen nearby 10(-3)Torr, leads to restrictions on the limiting thickness of condensates owing to occurrence of surface fragments exfoliations.

The results of investigations of the structure, hardness and mechanical resistance of TiN, Ti0.5Al0.5N, and Ti0.5-xAl0.5YxN (x <= 0,01) coatings deposited from the vacuum-arc source with the macroparticle filter at high voltage pulsed substrate bias are presented. All of the tested coatings are characterized with high hardness of 30 ... 36 GPa and erosion wear of low level. Doping of the Ti0.5Al0.5N coating with yttrium results in additional increase in its durability. The average rates of cavitation and erosion wear of the (Ti, Al)N+1at.%Y coating is 3-5 times lower than that of (Ti, Al)N one, and 10 times lower than that of TiN one. The influence of the low additions of yttrium on the structure and properties of the coatings are discussed.

It is shown, that insertion of silicon additives into TiN coatings and of yttrium into TiAlN coatings in explored limits (to a few wht. %) leads to increasing of rasistance against abrasive friction wear. At the same time silicon or yttrium presence in the coatings leads to loos of their columnar structure and demonstrate decrease in the cavitation resistance. It is supposed, that such distinction in behaviour of the given working performances is a consequence of that mechanisms of the coating surface fracture at action of cavitation and abrasive friction are diferent. All explored coatings of (Ti-Si)N composition are not oxidised up to 600 degrees C, and of (Ti-Al-Y) N coatings - up to 800 degrees C.