The use of electric arc or gas welding in the manufacture of titanium components often results in low quality welded joints due to large residual stresses and strains. A successful solution to this problem can be found in the application of friction stir welding. However, friction stir welding (FSW) of titanium alloys is complicated by rapid tool wear under high loads and temperatures achieved in the process. This paper studies the durability of a tool made of ZhS6U Ni-based superalloy used for friction stir processing of commercially pure titanium and the effect of the tool wear on the weld quality. The total length of the titanium weld formed by the tool without failure comprised 2755 mm. The highest wear of the tool is observed at the base of the pin, which brings about the formation of macrodefects in the processed material. The tool overheating causes an increase in the dendrite element size of ZhS6U alloy. The transfer layer contains chemical elements of this alloy, indicating that the tool wear occurs by diffusion and adhesion. As a result of processing, the tensile strength of commercially pure titanium increased by 25%.

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A review of the state of research in the field of friction stir welding and processing has been carried out. The features of plastic flow in friction stir welding and their connection with the processes of adhesion friction are shown. The main direction of research is related to the features of friction stir welding of titanium alloys. Special attention is paid to the selection of working tool materials from various alloys for friction stir welding and the processing of titanium alloys. The main advantages and disadvantages of applying different types of tools for friction stir welding of titanium alloys are shown. Different mechanisms of tool wear in friction stir welding associated with the interaction of processed material and tools are demonstrated. Information on the influence of tool and material interaction at welding on the mechanical properties and operational characteristics of obtained joints is given.

Friction stir welding (FSW) of titanium alloy was carried out using liquid cooling of the FSW tool made of heat-resistant nickel superalloy. Cooling of the nickel superalloy tool was performed by means of circulating water inside the tool. The FSW joints were characterized by microstructures and mechanical strength. The mechanical strength of the joints was higher than that of the base metal.

Titanium alloys are widely used in industry, especially (α+β)-alloys, among which Ti-6Al-4V alloy is the most popular one. Another common alloy that often appears in patents for titanium products is Ti-4Al-3Mo-1V. Here, we investigate welded joints of (α+β)-alloy Ti-4Al-3Mo-1V obtained by friction stir welding (FSW) using a working tool made of nickel-based heat-resistant alloy ZhS6U. In addition, welded joints of Ti-6Al-4V and Ti-4Al-3Mo-1V alloys with similar mechanical characteristics were considered. Mechanical tests showed that the obtained joints had a tensile strength greater than that of the base metal. This result was achieved in the welding mode where the axial load was varied during the welding process. X-ray diffraction analysis revealed a change in the phase structure of the welded joint.