Creep Behavior
Refractory metals and alloys attract the attention of investigators because of their remarkable properties and on account of promising practical prospects.
Physical properties of refractory metals, such as molybdenum, tantalum and tungsten, their strength, and high-temperature stability make them suitable material for hot metalworking applications and for vacuum furnace technology. Many special applications exploit these properties: for example, tungsten lamp filaments operate at temperatures up to 3073 K, and molybdenum furnace windings withstand to 2273 K.
However, poor low-temperature fabricability and extreme oxidability at high-temperatures are shortcomings of most refractory metals. Interactions with the environment can significantly influence their high-temperature creep strength. Application of these metals requires a protective atmosphere or coating.
The refractory metal alloys of molybdenum, niobium, tantalum, and tungsten have been applied to space nuclear power systems. These systems were designed to operate at temperatures from 1350 K to approximately 1900 K. An environment must not interact with the material in question. Liquid alkali metals as the heat transfer fluids are used as well as the ultra-high vacuum.
The high-temperature creep strain of alloys must be limited for them to be used. The creep strain should not exceed 1–2%. An additional complication in studying creep behavior of the refractory metals is interactions with environment, which can significantly influence the creep behavior.
Read more about this topic: Refractory Metals
Famous quotes containing the words creep and/or behavior:
“The awful shadow of some unseen Power
Floats though unseen among us, visiting
This various world with as inconstant wing
As summer winds that creep from flower to flower;”
—Percy Bysshe Shelley (1792–1822)
“The modern world needs people with a complex identity who are intellectually autonomous and prepared to cope with uncertainty; who are able to tolerate ambiguity and not be driven by fear into a rigid, single-solution approach to problems, who are rational, foresightful and who look for facts; who can draw inferences and can control their behavior in the light of foreseen consequences, who are altruistic and enjoy doing for others, and who understand social forces and trends.”
—Robert Havighurst (20th century)