Detection of microstructural changes of 9% Cr‐martensitic steels during heat treatment and aging by polarization tests

9–12% chromium martensitic steels are widely used as pipe material in steam power plants. Their good creep behavior is based on a finely adjusted microstructure, which is strengthened by precipitates. During long‐term use at higher temperatures degredation mechanisms occur, which affect the initial microstructure. Subgrain and precipitate coarsening as well as phase formation like Laves‐phase ((Fe, Cr)2(Mo, W)) proceed and lead to a reduced creep resistance. For lifetime assessment a nearly nondestructive electrochemical test method would be beneficial to identify microstructural changes during periodical inspections. The paper is focussed on the usability of an adapted electrochemical potentiodynamic reactivation (EPR)‐method and deals with the adjustment of test conditions like electrolyte composition and polarization parameters. The results obtained under optimized test conditions show a clear indication of precipitate formation by changing the characteristics of the EPR‐curves for the well established alloy T/P91 (X10CrMoVNb9‐1) as well as for the boron containing advanced alloy MARBN (X10CrWCoVNb9‐3‐3).     «

9–12% chromium martensitic steels are widely used as pipe material in steam power plants. Their good creep behavior is based on a finely adjusted microstructure, which is strengthened by precipitates. During long‐term use at higher temperatures degredation mechanisms occur, which affect the initial microstructure. Subgrain and precipitate coarsening as well as phase formation like Laves‐phase ((Fe, Cr)2(Mo, W)) proceed and lead to a reduced creep resistance. For lifetime assessment a nearly nond...     »