Vitaliy V. Samoylenko

The Structure and Corrosion Resistance of the Coatings Obtained by Non-Vacuum Electron Beam Cladding of the Ti-Nb Powder Mixture on a Titanium Substrates

In this study Ti-Nb coatings formed on the surfaces of cp-titanium plates by electron beam cladding were investigated. It was found that the coatings were characterized by a dendrite structure and a quenched structure was observed in the interdendritic space. The energy dispersive X-ray analysis revealed some differences between the elemental composition of different areas corresponding to dendritic crystals and the space between them. The corrosion resistance of the Ti-Nb alloy obtained on the titanium surface in the concentrated nitric acid was almost 8 times higher than the cp-titanium corrosion resistance.

Structure and Corrosion Resistance of Ti-Ta-Nb Coatings Obtained by Electron Beam Cladding in the Air-Atmosphere

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.

Structure and corrosion resistance of Ti-Nb layers obtained by non-vacuum electron-beam cladding on CP titanium substrates

Structural investigations and estimation of the properties of Ti-Nb layers fabricated by non-vacuum electron-beam cladding on the surfaces of cp-titanium substrates are carried out. It is found that the structure of the clad layers has mainly a dendritic morphology. At high magnification, the structure is characterized by a lamellar morphology. Defects, such as cracks, pores and undissolved niobium particles, are not observed. The microhardness of the alloyed surface layers is 3.5 GPa, the titanium substrate microhardness is 1.3 GPa. Electron-beam cladding of Ti-Nb layers contributes to a 35 times increase in corrosion resistance in a boiling nitric acid solution.

Structure and properties of surface-alloyed layers formed by non-vacuum electron beam cladding of Ta and Zr powders on commercially pure titanium plates

In this paper surface-alloyed layers formed on titanium VT1-0 substrates by non-vacuum electron beam cladding of Ta and Zr powder mixture are investigated. It has been found that the clad layers have a defect-free structure with a distinct dendritic segregation over the cross section of the layer. The tantalum and zirconium concentration in the clad layer is 17 wt. % and 20 wt. %, respectively. Electron beam cladding does not significantly reduce the fracture toughness of the “clad layer – titanium substrate” bimetallic composite; the value of fracture energy remained at a sufficiently high level of 172.9 J/cm2. The surface alloying of titanium with tantalum and zirconium allows the corrosion resistance of titanium in a boiling 5 % HCl solution to be increased 17.3 times.In this paper surface-alloyed layers formed on titanium VT1-0 substrates by non-vacuum electron beam cladding of Ta and Zr powder mixture are investigated. It has been found that the clad layers have a defect-free structure with a distinct dendritic segregation over the cross section of the layer. The tantalum and zirconium concentration in the clad layer is 17 wt. % and 20 wt. %, respectively. Electron beam cladding does not significantly reduce the fracture toughness of the “clad layer – titanium substrate” bimetallic composite; the value of fracture energy remained at a sufficiently high level of 172.9 J/cm2. The surface alloying of titanium with tantalum and zirconium allows the corrosion resistance of titanium in a boiling 5 % HCl solution to be increased 17.3 times.

Structure and mechanical properties of coatings fabricated by nonvacuum electron beam cladding of Ti-Ta-Zr powder mixtures

In this paper structural investigations and mechanical tests of Ti-Ta-Zr coatings obtained on surfaces of cp-titanium workpieces were carried out. It was found that the coatings had a dendrite structure; investigations at high-power magnifications revealed a platelet structure. An increase of tantalum concentration led to refinement of structural components. The microhardness level of all coatings, excepting a specimen with the maximum tantalum content, was 370 HV. The microhardness of this coating reached 400 HV. The ultimate tensile strength of cladded layers varied from 697 to 947 MPa. Adhesion tests showed that bimetallic composites were characterized by high bond strength of cladded layers to the substrate, which exceeded cp-titanium strength characteristics.

The Structure and Wear Resistance of the Surface Layers Obtained by the Atmospheric Electron Beam Cladding of TiC on Titanium Substrates

In this study the structure and properties of surface layers obtained on cp-titanium workpieces by non-vacuum electron beam cladding of titanium carbide powder were investigated. The structure of modified materials was examined by optical microscopy and scanning electron microscopy. It was shown that the cladded layer had a high quality and thickness of about 2.3 mm. The cladded layer microstructure consisted of high-strength titanium carbide crystals distributed in titanium matrix. Morphology of titanium carbide particles and their volume fraction changed in the direction from the surface layer to the heat affected zone. The average microhardness value of the cladded layer was ~500 HV. Surface alloyed layers were of higher wear resistance compared to cp-titanium.

Welding of a corrosion-resistant composite material based on VT14 titanium alloy obtained using an electron beam emitted into the atmosphere

The study investigates the possibility of inert gas arc welding of a double layer composite material on a titanium base with an anti-corrosive layer obtained by fused deposition of a powder mix containing tantalum and niobium over a titanium base using an electron beam emitted into the atmosphere. Butt welding and fillet welding options were tested with two types of edge preparation. Welds were subjected to a metallographic examination including a structural study and an analysis of the chemical and phase composition of the welds. A conclusion was made regarding the possibility of using welding for manufacturing of items from the investigated composite material.

Fabrication of Multi-Layered Ti-Ta-Zr Coatings by Non-Vacuum Electron Beam Cladding

In this study Ti-Ta-Zr coatings fabricated on VT1-0 titanium substrates by non-vacuum electron beam cladding in one, two and three passes were investigated. Coatings were characterized by a high quality; such defects as cracks and voids were not observed. The structure of coating was commonly dendritic. The acicular structure in the one-layered coating and in the first layer of multilayered coatings was revealed by using scanning electron microscopy (SEM). The results of the energy dispersive X-ray (EDX) analysis indicated the presence of tantalum and zirconium segregations in dendrite arms and in the space between them. It was found that dendritic branches contained the maximum of tantalum while an increased amount of zirconium was concentrated in the interdendritic space. The maximum concentration of alloying elements (56.87 wt. % Ta and 22.22 wt. % Zr) was obtained in the layer cladded in the third pass of an electron beam. The microhardness of Ti-Ta-Zr layers rose from 4.5 GPa to 6 GPa with an increase in .the percentage of alloying elements

The study of the modes of Ta-Zr powder mixture non-vacuum electron-beam cladding on the surface of the cp-titanium plates

The effect of the modes of non-vacuum electron-beam cladding of Ta-Zr powder mixtures on the structure and properties of the layers formed on the surface of cp-titanium were studied. The mode of the electron-beam alloying of titanium with zirconium and tantalum, which ensured the formation of a defect-free layer with a high content of alloying elements was selected. Metallographic examination indicated the presence of a dendritic- and plate-type structure of cladded layers. The microhardness of the layers, formed at the optimum mode, was not changed in the cross section and was equal to 450 HV.

Corrosion resistance of Ti-Ta-Zr coatings in the Boiling Acid Solutions

In this study corrosion resistance of Ti-Ta-Zr coatings fabricated on VT14 titanium alloy workpieces using a high-energy electron beam injected in the atmosphere was investigated. Estimation of corrosion resistance of surface alloyed layers was carried out by the weight-change method. Boiling solution of 65 % nitric acid in water and 5 % of sulfuric acid in water were used as the corrosive environments. Investigation of samples after corrosion tests was carried out using a Carl Zeiss EVO 50 XVP scanning electron microscope.