Oxidation behavior of in situ-synthesized (TiB+TiC)/Ti6242 composites

The oxidation behaviors of TiB and TiC particle-reinforced, titanium-matrix composites (TMCs) were studied in air at 550-650 degrees C, The oxidation kinetics follow approximately a parabolic rate law. The oxidation rates, which were lower than those of Ti6242, decrease gradually as oxidation proceeds. The oxide scales formed on TMCs were predominantly rutile and alpha-Al2O3. No B2O3 and other oxides were observed within the oxide scale. The in situ-synthesized TiB and TiC reinforcements can increase the oxidation resistance of TMCs. The oxide scales that formed exhibited excellent spallation resistance under all testing conditions. No scale cracking or spallation could be observed, implying that growth and thermal stresses generated during heating and cooling have been effectively released. The mechanisms of the decrease in oxidation rate and the improvement on spallation resistance are discussed based on microstructure studies.