Influence of heat treatment on corrosion resistance of martensitic stainless steels 1.4034 and 1.4021

摘要

In the last years, new approaches for the evaluation of the corrosion resistance of stainless steels were developed which allow short term corrosion testing with increased information content. This work analyses the extensive influence of heat treatment on microstructure and the resulting corrosion resistance of the martensitic stainless steels 1.4034 and 1.4021 with advanced methods. Different heat treatments at various austenitization temperatures up to 1100℃ and the effect of different cooling rates were evaluated; the last has not yet been studied in literature at all. The resulting corrosion behaviour in relation to the different carbon content in the two used alloys and the applied heat treatment will be presented and discussed. The applied methods of investigation were conventional evaluation of the critical pitting corrosion potential (PP), modified electrochemical potentiodynamic reactivation (mEPR) and the 'KorroPad' (KP) technique. The performance of modified EPR and its interpretation were optimized to provide additional information about the general passivation ability and the extent of chromium depletion as result of applied heat treatment. The aim using PP and KP was the correlation between the parameters of the mEPR with the changes in the pitting corrosion resistance. Furthermore the results will demonstrate the functionality and usability of the short term corrosion test methods mEPR and KP in order to increase their acceptance within the scientific community. The results indicate a surprisingly large influence of both austenitization temperature and cooling rate on the corrosion resistance within all three used test methods, which can explain the different corrosion behaviour of martensitic stainless steels in earlier investigations.