Abstract
The ratcheting boundaries of 316LN austenitic stainless steel under room temperature and 350 °C were determined by efficiency curve method. The iso-cumulative plastic strain curves of the material were obtained through numerical interpolation method. It is indicated that the primary stress and secondary stress range increase with the increase of cumulative plastic deformation. Under the same cumulative plastic strain, the iso-cumulative plastic strain curve at 350 °C is higher than that at room temperature. The effective primary stress was introduced to obtain ratcheting boundary curves. The results show that the material at 350 °C has a higher ratcheting boundary compared with that at room temperature. It is indicated that, under equivalent stress condition, the bearing capacity of 316LN at 350 °C is stronger than that at room temperature. This is due to the dynamic strain aging of the material at high temperature. At 350 °C, the solid solution atoms and dislocations are pinned together, which leads to a strengthening effect on the material. The ratcheting boundary curves determined in this study are compared with relevant standards. The test results suggest that the material served in different environments should be checked by different ratcheting boundary curves.
