Effect of Vacuum Environment on Creep-Rupture Properties of SUS 316 Stainless Steel at Elevated Temperatures
1976 Volume 25 Issue 277 Pages 991-997
Details
1976 Volume 25 Issue 277 Pages 991-997
The creep-rupture properties of SUS 316 stainless steel were studied in both air and vacuum of 10-3 torr at 600°C. In the test, unnotched and notched cylindrical specimens were used.
The following conclusions were obtained.
(1) The rupture lives of both unnotched and notched specimens in vacuum were shorter than those in air. Especially, a larger environmental effect was observed for unnotched specimens.
(2) The rupture time ratio, tr (notched) /tr (unnotched), in vacuum was larger than that in air. The environmental rupture time ratio, tr (air) /tr (vacuum), decreased with increase of stress concentration factor Kt.
(3) No difference between the structure of the crept unnotched specimen in air and that in vacuum was observed in terms of intergranular cracks, densities of elements in oxide layer, the size and distribution of precipitated Cr23C6 in the grain boundaries.
(4) It was considered that the remarkable increase of steady state creep rate in vacuum resulted from the increase of dislocation density or the associated lattice strain on the basis of the measurement of micro strain by X-ray diffraction technique.
