Improvement of the Long-Term Strength and Operating Life of Ti-Based Composites for High-Temperature Applications

Novel Ti-based composites are being developed for applications in power equipment and modern rocket and aircraft engines as they provide low specific weight simultaneously with high fracture toughness and strength in a temperature range of 20–700 °C. In this work, the creep behavior of Ti–Si–X composites aimed at high-temperature applications in power equipment was investigated. The material of the Ti–Si–X system (X = Zr and/or Al) was produced by melting using an electric arc furnace with the addition of fine alloying elements. Three variants of the material, which differed in silicon and aluminum content, were obtained. Billets of material after casting were machined to prepare cylindrical specimens. Creep tests of specimens were performed at temperatures of 600, 700, and 800 °C in air at various levels of engineering stress. It was found that at medium levels of engineering stress, all materials demonstrated classical creep behavior, and the creep curve contained three characteristic sections: deceleration, steady-state creep, and accelerated failure. Average creep rates for the applied levels of engineering stress were estimated in the sections of steady-state creep. Based on the fracture analysis of the specimens, characteristic patterns of temperature-dependent creep of Ti–Si–X composites were noted. Using XRD analysis, the phase content and percentage of the main phases were determined and consolidated with the creep parameters (stress, creep rate) for the corresponding composites. The dominant micromechanisms of strengthening and the role of silicides in achieving appropriate levels of long-term strength and increasing the operating life of the Ti-based composites aimed at high-temperature applications are discussed.