ISOTHERMAL OXIDATION BEHAVIOR OF MO-SI-B INTERMETALLICS AT 1450-DEGREES-C

Five Mo-Si-B multiphase intermetallic compositions were synthesized an d oxidized isothermally at 1450 degrees C in flowing air, Average mass change rates were strongly dependent on sample composition, particula rly boron content, An Mo5Si3 matrix material containing 1.6 wt% boron exhibited parabolic mass gain with a rate of 5.3 x 10(-4) mg(2)/(cm(4) . h), while a similar material with 0.14 wt% boron oxidized rapidly i n a linear manner at a rate of -3.3 mg/(cm(2) . h). Oxidation rates of the Mo-Si-B intermetallics were compared to that of MoSi2 oxidized at 1450 degrees C under identical conditions.