Corrosion Behavior of Plasma Nitrided and Nitrocarburised Supermartensitic Stainless Steel

Authors

Frederico Augusto Pires Fernandes, Universidade Federal do ABC
Carlos Alberto Picone, Universidade Estadual Paulista
George Totten, Portland State UniversityFollow
Luiz Carlos Casteletti, Universidade de São PauloFollow

Published In

Materials Research

Document Type

Article

Publication Date

3-2018

Subjects

Martensitic stainless steel -- Technological innovations, Nitriding, Plasma engineering, Corrosion

Abstract

Supermartensitic stainles steels (SMSS's) are a new generation of martensitic steels that have been increasingly used in oil and gas applications due to their adequate corrosion resistance and mechanical properties. In the present study, SMSS specimens (UNS S41425) were solution heat treated and air cooled followed by plasma nitriding and nitrocarburising at 400, 450 and 500°C for 5h. The produced layers were characterized by optical microscopy, microhardness testing, X-ray diffraction and corrosion testing in NaCl 3.5% solution. Surface alloying with nitrogen or both nitrogen and carbon results in increased surface hardness and homogeneous layers in which layer thickness increases with temperature. However, plasma nitriding yields a slightly thicker case than nitrocarburising. X-ray diffraction indicates very broad and overlapped peaks for the treatments conducted at 400°C. Increasing treatment temperature appears to result in the formation of chromium nitrides and iron nitrides and carbides, depending on the treatment. It was also found that treatment temperature drastically affects the corrosion response of the steel. The untreated steel presented a pitting potential close to 250mV. Plasma nitriding at 400°C was the only condition in which significant improvement of corrosion is observed. For plasma nitriding and nitrocarburising at 450 and 500°C, some pitting was detected.

Description

Originally appeared in Materials Research, volume 21, number 3, 2018. May be found at http://dx.doi.org/10.1590/1980-5373-mr-2016-0793.

DOI

10.1590/1980-5373-MR-2016-0793

Persistent Identifier

https://archives.pdx.edu/ds/psu/25876

Citation Details

Fernandes, Frederico Augusto Pires, Carlos Alberto Picone, George Edward Totten, and Luiz Carlos Casteletti. "Corrosion Behavior of Plasma Nitrided and Nitrocarburised Supermartensitic Stainless Steel." Materials Research 21, no. 3 (2018).