Effect of nitrogen on microstructure and corrosion resistance of Cr15 super martensitic stainless steel

ABSTRACT

To investigate the influence of nitrogen on structure and corrosion resistance of Cr15 super martensitic stainless steels (SMSS), two types (N-free and N-0.12%) of specimens were quenched at 1050°C and tempered at different temperatures, and then, optical microscope, transmission electron microscopy, X-ray diffraction, potentiodynamic polarisation, immersion experiments and Kelvin Probe Force Microscope were used to characterize its microstructures and corrosion properties. The experimental results show that the microstructure in the N-free Cr15 super martensitic stainless steel is a biphasic tissue with alternating martensite and austenite distribution while quenched at 1050°C and tempered between 600 and 700°C. The nitrogen addition increases the content of austenite, and changes the austenite morphology significantly into the coarse block and strip distribution. What’s more, micro-galvanic corrosion is formed between austenite and martensite, which deteriorates the corrosion resistance of the SMSS.

KEYWORDS:

• Super martensitic stainless steel
• nitrogen
• austenite
• galvanic corrosion

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge support from National Key R&D Program of China [2016YFB0300204], National Natural Science Foundation of China [grant number U1806220] and National Natural Science Foundation of China [grant number U1660114].