Low-temperature plasma nitriding of AISI F51 duplex stainless steel

Author(s)

Pinedo, Carlos Eduardo ^[1] ; Varela, Luis Bernardo ^[2] ; Tschiptschin, Andre Paulo ^[2]

Affiliation

^[1] Heat Tech Technol Heat Treatment & Surface Engn L, BR-08830000 Mogi Das Cruzes, SP - Brazil

^[2] Univ Sao Paulo, Met & Mat Engn Dept, BR-05508900 Sao Paulo - Brazil

• Document type: Journal article
• Source: SURFACE & COATINGS TECHNOLOGY; v. 232, p. 839-843, OCT 2013.
• Web of Science Citations: 12

Abstract

AISI F51 duplex stainless steel, with aligned ferrite and austenite stringers, was DC-plasma nitrided at 400 degrees C, in a 75% N-2 + 25% H-2 atmosphere. A modulated nitrided layer formed on the specimen's surface, the nitrided layer on the ferritic regions being thicker than on the austenitic regions of the microstructure. X-ray diffractometry and electron backscattered diffraction patterns (EBSD) revealed two phases in the nitrided layer: expanded austenite (gamma(N)) formed on the surface of austenite grains and expanded ferrite (alpha(N)) formed on the surface of ferrite grains. The nitrogen contents of both expanded phases were measured by wavelength dispersive X-ray diffractometry (WDX), being 3.8 wt.% in expanded austenite and 4.4 wt.% N in expanded ferrite. N supersaturation led to the strong hardening of the surface, up to 1350 HV. Microhardness profiles of the nitrided layer, measured on ferrite and austenite stringers, allowed estimating the nitrided layer thicknesses of each of the expanded phases. The expanded ferrite regions (alpha(N)) showed very fine deformation bands while the expanded austenite regions showed slip lines formed as a consequence of large compressive stresses developed in the nitrided layer. (C) 2013 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 11/16211-5 - Evolution of the micro/nanostructureof high nitrogen stainless steels, related to the deformation mechanisms on the cavitation erosion resistance of stainless steels
• Grantee: Luis Bernardo Varela Jiménez
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 12/50890-0 - Improvement of surface properties of stainless steel used in the oil and gas industries through plasma assisted thermochemical treatment
• Grantee: Andre Paulo Tschiptschin
• Support Opportunities: Regular Research Grants