Atmospheric electron-beam surface alloying of titanium with tantalum

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 CaF2 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.