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.
The cladding of titanium and graphite powders on the cp-titanium workpieces using the electron beam injected to the atmosphere provided the formation of the surface layers with a high content of high-strength carbide particles. The main structural components in cladded layers are α-Ti (αʹ-Ti), titanium carbide and graphite. Electron beam current is the main technological parameter defining a thickness of the hardened layer. An increasing beam current ranged from 20 to 23 mA leads to the cladded layer growth up to 2.9 mm. However, in this case a significant decrease of the microhardness level and the wear resistance level of the cladded layer is not observed. An average microhardess value of the hardened layer is of 430 HV. Under the conditions of friction against fixed abrasive particles, a wear resistance level of the cladded layers is by 32-45 % larger than that of cp-titanium.
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