화학공학소재연구정보센터
Materials Chemistry and Physics, Vol.207, 203-211, 2018
Effect of grain size on self -healing behaviour of sensitized S304HCu stainless steel
S304HCu stainless steel is extensively used for superheater and reheater applications in power plants due to its superior creep strength and oxidation resistance which are derived from the coherently dispersed precipitates formed in austenite matrix. In addition to the beneficial precipitates, chromium carbide precipitates can also form. Formation of chromium carbide precipitates during service will lead to sensitization. In this investigation, S304HCu samples were solutionized at 1100 degrees C and 1200 degrees C for 1 h, and further aged at 750 degrees C for upto 400 h to introduce sensitization and subsequent healing. The influence of ageing time and grain size on the degree of sensitization (DOS) was evaluated by using oxalic acid and double loop electrochemical potentiodynamic reactivation (DLEPR) tests. DOS initially increased up to 10 h of ageing and subsequently was reduced due to healing and attained a steady value at 50 h. Faster and higher DOS was observed in coarse grain structure than in the fine grain structure. However, healing was largely delayed in coarse grained structure. The difference in solute and excess vacancy concentration and shifting of the nose in TTP curve were attributed to the difference in the kinetics of sensitization and healing. The extent of the attack on the grain boundary was analyzed using AFM. (C) 2017 Elsevier B.V. All rights reserved.