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The study has been conducted in line with the current approach to investigation of materials obtained by considerably deep surface alloying of the titanium substrate with Ta, Nb, and Zr. The thickness of the resulting alloyed layer was equal to 2 mm. The coating was formed through weld deposition of a powder with the use of a high-voltage electron beam in the air. It has been lately demonstrated that manufactured such a way alloyed layers possess corrosion resistance which is significantly higher than the resistance of titanium substrates. It has already been shown that such two-layered materials are weldable. The study objective is to investigate the feasibility of rolling for necking the sheets with the Ti-Ta-Nb anticorrosion coating with further fourfold decrease in their thickness. The research is also aimed at investigation of the material properties after rolling. Anticorrosion layers were formed both on CP-titanium and on VT14 (Ti-4Al-3Mo–1 V) durable titanium alloy. The results of chemical composition determination, structure examination, X-ray phase analysis and mechanical properties observations (including bending properties of the alloyed layers) are presented in the paper. The combination of welding, rolling, and bending enables the manufacture of corrosion-resistant vessels and process pipes which are made from the developed material and find technological application.

Titanium and titanium alloys are highly important structural materials for many industries where low density in combination with high mechanical strength and corrosion resistance are required. However, titanium is not applicable for tribological or high temperatures purposes due to its interaction with atmospheric gases and friction seizure during the contact with most metallic materials. To protect the surface of titanium and improve its wear resistance intermetallic coatings can be applied. In this study, the Ti-Al intermetallic layers were fabricated on Ti surface by electron beam melting of Al and Ti powders. By variation of Al/Ti ratio in the initial powders it was possible to control elemental and phase composition of the layers. The formation of TiAl, Al2Ti and Ti3Al phases was observed in the layers. Independently on Al content the layers had lamellar type of structure. Microhardness, wear resistance and oxidation resistance were measured to evaluate the quality of the layers. The microhardness and wear resistance were in good agreement with each other. The coating, consisted of pure Ti3Al phase, demonstrated the highest level of these properties. Oxidation resistance of the coatings increased proportionally to the aluminium content due to formation of alumina in oxide scale.

Ti-Al-Nb based intermetallic layers of sufficient quality and thickness were obtained by non-vacuum electron beam cladding on the surfaces of Ti workpieces. Optical microscopy and X-ray tomography did not reveal any dramatical defects in the structure of cladded layers. X-ray diffraction as well as scanning and transmission electron microscopy were applied to thoroughly investigate the structure and phase composition of coatings. It was found that non-equilibrium cooling conditions of coatings provided by fast removal of heat to untreated Ti substrate after the electron beam cladding was terminated induced the proceeding of metastable phase transformations. For example, γ-phase formation was suppressed in these coatings. In coatings with 8 and 20 at.% Nb (46 and 43% Al respectively) along with ordered with α2, formation of disordered solution of the alloying elements in α-Ti took place. In high-Nb alloys β(B2) phase has undergone the diffusionless transformation to ω’, which is the intermediate phase in β → ω and the coating with the maximum Nb content characterized by appearance of γ1 as a main phase. ω-phase had negative influence to hardness and wear resistance of coatings, however, generally this paremeter increased in 1.3–1.75 times compared to cp-Ti. The high temperature creep and oxidation properties decreased proportionally with increasing Nb and decreasing Al content in the cladded layers.

In this work, we present a wear-resistant coating fabricated by non-vacuum electron beam cladding of Fe62Cr10Nb12B16 at.% powder on a mild steel substrate. The protective coating was 1.3 mm thick, dense, and exhibited an α-(Fe,Cr) matrix reinforced by a significant fraction of hard borides formed upon solidification. Micrometric and nanometric borides homogeneously dispersed within the matrix were formed due to the homogeneous melting and the relatively fast cooling to suppress the excessive phase growth. An intimate metallurgically bonded interface between the coating and substrate was characterized by low compositional dilution and a fine eutectic-like transition zone microstructure anchoring the dissimilar materials. The coatings displayed a higher wear resistance compared to the mild steel substrate, showing specific wear rates, κ, about one order of magnitude lower (10−5 against 10−4 mm3/N.m, respectively). The abrasive wear mechanism was dominant for the coating sample when tested at low sliding velocity, 10 cm/s, due to the detachment of hard borides from the surface and their incorporation into the tribosystem. The adhesive wear mechanism was found to be dominant at higher sliding velocities of 20 and 40 cm/s. Dry sand/rubber wheel testing revealed the higher resistance of the coating against abrasive wear compared to the mild steel substrate. Regardless of the wear mechanism, the Fe62Cr10Nb12B16 at.% coatings showed a superior sliding and abrasive wear resistance and represented an interesting protective measure to extend the service of inexpensive mild steel components.

A method of surface alloying of titanium substrates with tantalum in order to obtain corrosion-resistant layers is described. An electron beam injected into the atmosphere is used as a power source. A powder layer containing a composition of alloying components and a fluxing agent was placed on the surface of a Ti plate. The plate exposed to a scanning beam was moved at a speed of 1cm/sec. The scanning range was 5cm, the scanning frequency was 50 Hz and the beam power was 33.5 kW. To enhance the degree of alloying the coating procedure was repeated up to 4 times. Alloyed layers 2-3 mm thick containing up to 40 wt % Ta were obtained. The rate of corrosion in HNO3 depends on the Ta concentration in the deposited material. It is tens and hundreds times lower than the rate of corrosion of unalloyed titanium for all coatings. Surface deposition by the proposed method can be used to protect internal surfaces of chemical reactors operating in media containing aggressive acids at increased temperatures up to the boiling temperature.

This paper presents the results of studies of the structure and properties of coatings produced by cladding 10 mm thick titanium plates with titanium–tantalum powder mixtures using an electron beam extracted into air. A mixture of CaF 2 and LiF salts was used as a flux that protected the heated material from the air atmosphere. The electron beam power was 33.5 kW, the velocity of the sample relative to the beam 10 mm/s, and the beam scanning frequency 50 Hz. High-performance titanium–tantalum layers 2–2.5 mm thick with a tantalum content of 3.9–22.4 wt% were obtained. The surface layers have a dispersed α(α′)+β structure. The tensile strength of the alloy containing 3.9% tantalum is 620 MPa. Increasing the Ta content to 22.4% increases the tensile strength to 735 MPa. For the coating material containing 22.4 wt% Ta, the rate of corrosion in a 68% solution of boiling nitric acid was 190 times lower than that for unclad titanium. The conditions of formation of the layer structure by high-velocity electron-beam cladding of powder materials are significantly different from equilibrium. For this reason, the resulting materials are characterized by a number of features, including a high degree of dispersion of the structural components and inhomogeneous chemical composition.

This paper presents a brief review of research made by the authors to determine feasibility of using a titanium-based bilayer material in industrial applications. One layer, corrosion preventive, is formed by surface alloying with highly corrosion-resistant doping elements, in particular, Ta, Nb and Zr. These elements have significantly higher corrosion resistance than titanium. Applying them on the titanium substrate allows formation of a coating resistant, in particular, to boiling strong acids. Resistance of obtained coatings in said media is many times higher than that of titanium or stainless steel. The coatings are formed using a high-penetration electron beam ejected to the atmosphere. This article contains references to findings of previous works and offers some new data.