Compositional Factors Affecting the High-Temperature Degradation Behavior of Alloys Exposed to Relatively High P_(s2) - Low P_(o2) Atmospheres

摘要

The sulfidation rates of most metals and alloys are generally 10~4-10~6 times higher than their oxidation rates, depending on temperature (i.e., the activation energies are different). As a result, the maximum temperature for long-term service of metallic materials exposed to high- P_(s2) - low P_(o2) environments, such as those associated with low-NO_x combustion systems, is generally considered to be about 600°C (much lower than for oxidizing environments). However, as determined in this study, the extent of sulfidation attack of a given alloy is critically dependent on the amounts of Cr and base-metal constituents - Fe, Ni and Co. The relative proportions of base-metal constituent greatly affect the duration to breakaway attack and the nature of the reaction product formed. The alloy composition also significantly influences the location of the so-called kinetic boundary.