Oxidation behavior of Moss–Ti5Si3–T2 composites at intermediate and high temperatures

Abstract

Three Mo–Ti–Si–B-based alloys with the compositions of 35Mo–35Ti–20Si–10B, 35Mo–35Ti–15Si–10B–5Al and 32.5Mo–32.5Ti–20Si–10B–5Cr (at.%) were designed and produced by arc-melting in argon atmosphere, and their oxidation behavior was investigated at temperature between 700 °C and 1100 °C. All the alloys were composed of three phases, i.e., Mo-rich solid-solution, Ti5Si3 and Mo5SiB2. Specific weight change against oxidation time was obtained at both intermediate and high temperatures. A rapid mass loss occurred in the initial period of oxidation, after which the oxidation rate gradually decreased and sometimes even stayed stable. The total mass loss within 24 h was less than 2.0 mg/cm2 at all testing temperatures for all compositions. All the alloys demonstrated a relatively good oxidation resistance at intermediate temperatures, which was attributed to the relatively low viscosity of the borosilicate glass in the TiO2-borosilicate duplex scale. Pest phenomenon or spalling of the oxide scale did not occur for all alloys, and Al- or Cr-addition improved the oxidation resistance at intermediate temperatures through microstructure revolution. Continuous Al- or Cr-oxide layer was not observed on the alloys even after they were oxidized at high temperature. Besides, 32.5Mo–32.5Ti–20Si–10B–5Cr (at.%) had the best oxidation resistance at 1100 °C in this study because a dense borosilicate-matrix duplex layer formed on this alloy.