Improvement of the mechanical properties of gas turbine engine parts made of two-phase titanium alloys

Abstract

The subject of this study is the features of weld seam formation in complex alloyed titanium alloys during electron beam welding in a vacuum and argon arc welding. The aim of this research is to ensure the required level of mechanical properties of welded joints for aviation and aerospace components made from complex alloyed two-phase titanium alloys. The objectives are: to analyze the mechanisms of structure formation to ensure the necessary level of mechanical properties of welded joints from titanium alloys; to investigate the effect of fusion welding on the structure and mechanical properties of complex alloyed titanium alloys. Research results. It was found that the weld metal forms a structure with a predominance of metastable β-phase, which leads to a reduction in plasticity and impact toughness. The best combination of strength and plasticity of the investigated welded joints was obtained after heat treatment. The use of filler wire helps to achieve a nearly homogeneous structure and the decomposition of metastable phases in the weld and heat-affected zone, resulting in a tensile strength of 1250 MPa. Conclusions. It was established that the weld seams form an unregulated, coarse-grained lamellar structure, with the size of the primary β-phase ranging from 180 to 300 µm. The size of the heat-affected zone for argon arc welding is 5 mm, and for electron beam welding, it is 2 mm. The study of the mechanical properties and the nature of the failure of the welded joints showed that structural changes during fusion welding lead to a reduction in mechanical properties, with the strength of the obtained welded joints being no more than 80-85% relative to the strength of the base metal. The absence of structural changes during electron beam welding preserves the level of mechanical properties, with the strength of the obtained welded joints from high-strength titanium alloys being more than 90% relative to the base metal.