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The aim of this investigation was to study the influence of Nb-enriched powder mixtures on structure and oxidation resistance of protective layers based on Ni-based self-fluxing alloy, produced by non-vacuum electron beam cladding technique on low-carbon steel substrates. The oxidation resistance of coatings was studied by thermogravimetric analysis (TGA). The samples held at 900°C for two hours in air atmosphere. TGA results indicate that the highest oxidation resistance has the material, obtained by cladding of pure Ni-based self-fluxing alloy. Samples, produced by cladding of Ni-based self-fluxing alloy in combination with Nb-enriched powder mixtures demonstrate lower level of oxidation resistance. Structure of the coatings was characterized by optical and scanning electron microscopy combined with electron microprobe analysis as well as X-ray diffraction.

The effect of Nb content on microstructure, mechanical properties and phase formation in as-melt and annealed binary Ti-Nb alloys were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. The content of Nb varied in the range 25-35 mass % leading to significant changes in the microstructure. The annealed and furnace-cooled binary Ti-Nb samples exhibited HCP martensitic α` phase at a Nb content below 27.5 mass % and metastable BCC β phase at higher contents of Nb. The mechanical properties of alloys depended strongly on the Nb content and type of the dominating phase.

This paper is devoted to the investigation of structure and properties of Ti-Ta-Mo layers produced on the surface of commercially pure (cp) titanium using non-vacuum electron beam processing. Due to electron-beam surface alloying, a thick defect-free layer with increased hardness was produced. The average concentration of Ta and Mo was 22 % (wt.) and 9 % (wt.) respectively, which led to the formation of the β-Ti matrix with nanoscale precipitation of the ω-phase. The electron backscatter diffraction (EBSD) study revealed the formation of a cubic texture along the direction ofβ-Ti normal to the sample surface, during crystallization of the surface layer. The results of this study can be used to predict the properties, particularly, the Young modulus of surface alloyed titanium, which may be of interest for biomedical application.

The possibility of joining titanium substrates with Ti-Ta corrosion-resistant coatings was investigated. Joints were obtained by manual tungsten inert gas welding. Microstructure investigations revealed the inhomogeneous distribution of alloying elements and a martensitic microstructure in joints. Microhardness values in Ti-Ta coatings and welded seams were approximately equal and varied from 380 to 420 HV. The value of titanium substrate microhardness was about 180 HV. An ultimate strength of welded joints was equal to 580 MPa while the strength of the starting material was 365MPa.

The results of structural investigations, mechanical properties and corrosion resistance testing of materials produced by the electron beam cladding of tantalum and niobium powders on cp-titanium substrates are presented in this paper. The treatment resulted in the formation of remelted alloyed layers of ~2 mm thickness. Any voids or cracks were not observed in coatings. Dendritic segregation of alloyed elements during cladding process occurred, however the microstructure was represented by fine laminar-type crystals. X-ray diffraction analysis showed the presence of α’-, α”- and β-phases. Formation of such structure is explained by a high crystallization rate. Microhardness of cladded layers was equal to ~ 350 HV while the base material hardness level was 170 HV. The corrosion resistance was estimated based on the sample mass loss. A concentrated solution (68%) of HNO3 at the boiling temperature was used as a corrosion medium. It was found that alloying the titanium with 16 wt. % Ta and 5 wt. % Nb decreased the corrosion rate by factor of 24 against cp-titanium while adding 16 wt. % Ta and 16 % wt. Nb decreased the corrosion rate by factor of 96.

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.