Effect of 6-ferrite on the corrosion resistance of the 9Cr high nitrogen heat-resistant martensitic-steel

The effect of 6-ferrite on the mechanical properties and corrosion of martensitic steel is controversial, owing to the difficulty in studying the role of 6-ferrite and the segregated carbides separately. Herein, we investigate the role of 6-ferrite in the corrosion resistance of the high nitrogen heat-resistant martensitic-steel (HNHM), which is strengthened by well distributed nitrides, substituting the segregated carbides. 6-ferrite with much higher surface potential (~50 mV) than martensite, accelerates the formation of adherent corrosion layer at the initial state of corrosion, causing the corrosion inhibition and resulting in slow corrosion. Additionally, the formation of highly protective film originates from the similar alloy-elements distribution except for N between both 6-ferrite and martensite.

Automated summary

It has been found that 6-ferrite can accelerate the formation of adherent corrosion layer in high nitrogen heat-resistant martensitic steel, thereby improving the corrosion resistance of the steel.