In this paper, phase transitions and microstructure evolution in titanium Ti-6Al-4V alloy parts produced by electron beam melting (EBM) under hydrogenation was investigated. Hydrogenation was carried out at the temperature of 650 °C to the absolute hydrogen concentrations in the samples of 0.29, 0.58, and 0.90 wt. %. Comparative analysis of microstructure changes in Ti-6Al-4V alloy parts was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Furthermore, in-situ XRD was used to investigate the phase transitions in the samples during hydrogenation. The structure of Ti-6Al-4V parts produced by EBM is represented by the α phase plates with the transverse length of 0.2 μm, the β phase both in the form of plates and globular grains, and metastable α″ and ω phases. Hydrogenation to the concentration of 0.29 wt. % leads to the formation of intermetallic Ti₃Al phase. The dimensions of intermetallic Ti₃Al plates and their volume fraction increase significantly with hydrogen concentration up to 0.58 wt. % along with precipitation of nano-sized crystals of titanium δ hydrides. Individual Ti₃Al plates decay into nanocrystals with increasing hydrogen concentration up to 0.9 wt. % accompanied by the increase of proportion and size of hydride plates. Hardness of EBM Ti-6Al-4V alloy decreases with hydrogen content.

Influence of manufacturing parameters (beam current from 13 to 17 mA, speed function 98 and 85) on microstructure and hydrogen sorption behavior of electron beam melted (EBM) Ti-6Al-4V parts was investigated. Optical and scanning electron microscopies as well as X-ray diffraction were used to investigate the microstructure and phase composition of EBM Ti-6Al-4V parts. The average α lath width decreases with the increase of the speed function at the fixed beam current (17 mA). Finer microstructure was formed at the beam current 17 mA and speed function 98. The hydrogenation of EBM Ti-6Al-4V parts was performed at the temperatures 500 and 650 °С at the constant pressure of 1 atm up to 0.3 wt %. The correlation between the microstructure and hydrogen sorption kinetics by EBM Ti-6Al-4V parts was demonstrated. Lower average hydrogen sorption rate at 500 °C was in the sample with coarser microstructure manufactured at the beam current 17 mA and speed function 85. The difference of hydrogen sorption kinetics between the manufactured samples at 650 °C was insignificant. The shape of the kinetics curves of hydrogen sorption indicates the phase transition α_H + β_H→β_H.

Metallic Cr and multilayer CrN/Cr coatings with a thickness of 2.5 µm were deposited onto E110 alloy by magnetron sputtering. Oxidation tests in air were performed at 1100 °C for 10–40 min. The gravimetric measurements showed better protective properties of multilayer CrN/Cr coatings in comparison with metallic Cr coating. Multilayer coating prevented fast Cr–Zr inter-diffusion by the formation of a ZrN layer beneath the coating. The appearance of ZrN is caused by interaction with nitrogen formed from the decomposition of CrN to Cr₂N phases. Optical microscopy revealed a residual Cr layer for the multilayer CrN (0.25 µm)/Cr (0.25 µm) coating for all the oxidation periods. Additional in situ X-ray diffraction (XRD) studies of coated alloy during linear heating up to 1400 °C showed that the formation of the Cr₂Zr phase in the case of multilayer coatings occurred at a higher (~150 °C) temperature compared to metallic Cr. Multilayer coatings can decrease the nitrogen effect for Zr alloy oxidation. Uniform and thinner oxide layers of Zr alloy were observed when the multilayer coatings were applied. The highest oxidation resistance belonged to the CrN/Cr coating with a multilayer step of 0.25 µm.

The oxidation resistance under LOCA conditions of bilayer Cr/Mo coating deposited on Zr-1Nb zirconium alloy was investigated in this paper. The bilayer Cr (8 μm)/Mo (3 μm) coatings were deposited by magnetron sputtering. Then, oxidation resistance under high-temperature oxidation at 1200–1400 °C in a water steam was studied. The use of a Mo sublayer resulted in limiting Cr-Zr interdiffusion under high-temperature oxidation. It was shown that the Mo barrier sublayer (~3 μm) can provide the protective behavior of the Cr/Mo-coated Zr at 1330 °C in a water steam for at least 720 s. The weight gain of the bilayer Cr/Mo samples was comparable with the monolayer Cr samples after oxidation at 1400 °C. In addition, the analysis of the Cr/Mo-coated Zr alloy oxidation behavior at 1400 °C was carried out.

In this work, a laboratory X-ray diffraction complex for in situ investigations of structural phase evolution of materials under gaseous atmosphere and elevated temperatures was developed. The approbation of the complex was carried out using a commercially pure titanium (CP-Ti) powder, zirconium (Zr-1Nb) alloy and electron beam melted Ti-6Al-4V alloy. It was established that hydrogenation of the CP-Ti powder occurred at a temperature of 500 °C and a hydrogen pressure of 0.5 atm, accompanied by the formation of metastable γ titanium hydride (γ-TiH) phase. The lifetime of the γ-TiH phase was 35–40 min. Decomposition of the γ-TiH occurred after reaching a temperature of 650 °C as a result of the thermally stimulated desorption of hydrogen. The α-Zr → δ-ZrH phase transformation was observed under hydrogenation of the zirconium Zr-1Nb alloy at a temperature of 350 °C and a hydrogen pressure of 0.5 atm. It was revealed that the increase in hydrogenation temperature to 450 °C accelerated this transformation by two times. Hydrogenation of the electron beam melted titanium Ti-6Al-4V alloy at a temperature of 650 °C and hydrogen pressure of 0.5 atm was accompanied by the α → α + β → β + α₂ phase transformations.

The paper presents the study results of CrN/TiN multi-layer coatings, as well as single-layer TiN and CrN coatings on Cr12MoV cold work die steel deposited by the vacuum-arc plasma-assisted method. Three CrN/TiN coatings of 8-, 16-, and 32-layers were deposited, in which the thickness of each layer was 500 nm, 250 nm and 125 nm, respectively. All of the coatings reveal a face-centered cubic structure with highly oriented (111) growth. The hardness of the CrN/TiN multi-layer coatings was about 27 GPa. Changing the architecture of CrN/TiN multi-layer coatings by reducing the thickness of the CrN and TiN layers from 500 nm to 125 nm promotes a smooth decrease in both the wear parameter and the coefficient of friction. By using an X-ray phase analysis with synchrotron radiation, it was found that 32-layer CrN/TiN coating retained thermal stability during heating in air to a temperature of 1120–1125 °C, and in a vacuum at least to a temperature of 1200 °C.