Abstract
The effect of grain size, ranged from 22 to 404μm, on the creep behavior of carbon free 17Cr-14Ni steel was studied at the temperature of 850 and 900°C.
The creep properties, mainly steady state-or minimum-creep rate, strongly depend on the grain size, that is, 1) steady state creep rate, ∈s, is independent of grain size for the grain sizes from 100 to 200μm, where ∈s reaches the minimum, 2) below about 100μm, ∈s increases with the decrease of grain size, whereas, 3) above about 200μm, ∈s increases with the increase of that.
From the measurement of internal stress (σi) and the observation of the microstructures, it was concluded that under the constant applied stress the increase in ∈s with the decrease of grain size is attributable to the increase of effective stress, σe=σa-σi, where σa is the applied stress.
On the other hand, the recrystallization at the grain boundary triple points between large grains induced by the stress concentration seems to increase ∈s with the increase of grain size above 200μm.
