Oxidation resistance and microstructure of the oxide layers for TiB2-based cermets

Abstract

The oxidation behaviour of several TiB 2 cermets has been studied in air in a range of temperatures between 700 and 1000 °C for up to 70 h. The oxidation resistance of these materials has been characterised through measurements of mass gain as a function of time and temperature. The oxidation kinetics of these cermets was observed to change from a parabolic to a linear type at temperatures between 750 and 775 °C. Activation energies were observed to be 170-185 and 109-123 kJ mol−1 for the parabolic and linear ranges, respectively. The oxidation products and the microstructure of the oxide scales formed after these oxidation treatments were characterised by XRD and SEM. Table 1 Chemical composition (wt%) of the experimental cermets

Cyclic oxidation behavior of TiAl composites incorporated with TiB2 dispersoids

“…6(c)). It is known that TiB 2 oxidizes to TiO 2 and B 2 O 3 which has an appreciable vapor pressure at high temperatures [25][26][27][28].…”

Improving Hardness and Toughness of Boride Composites Based on AIMgB₁₄

“…Chemical analysis shows that even with approximately half the Fe concentration, the MM powder still sintered to slightly higher densities. In many cases, large amounts of metallic binders are added to TiB 2 powders to aid in sintering, often exceeding 10 wt% [67][68][124][125]. It has been…”

“…Metallic binders are particularly troublesome. Whether added for liquid or solid state sintering, most metals will react to form a number of different borides with lower strength and hardness than TiB 2 ; also, reaction of the binder eliminates the possibility of a ductile, toughening phase [65][66][67][68].…”

“…Significant amounts of metallic binders, nitrides, and/or carbides are typically used as sintering aids [63][64][65][66][67][68]. While these additions decrease porosity, they are largely detrimental to mechanical properties compared to monolithic TiB 2 .…”

“…Due to the refractory nature of this material, high-temperature powder consolidation methods such as HIP or hot-pressing are generally required. In order to obtain nearly fully dense material, sintering temperatures of 1800ºC or higher are usually needed unless large additions of sintering aids, especially metallic, are used [63][64][66][67][68][123][124][125]. Studies have shown that small additions of Si 3 N 4 or metallic elements such as Fe or Ni perform exceptionally well at reducing the temperatures and pressures required to sinter TiB 2 to near 100% density [102,126].…”