Title: Deformation and fracture analysis of nitrided steels by acoustic emission measurement

Authors: Sergey Nikulin; Anatoliy Nikitin; Vladimir Khatkevich; Stanislav Rogachev

Addresses: Department of Physical Metallurgy and Physics of Strength, The National University of Science and Technology "MISIS", Leninsky pr. 4, 119049 Moscow, Russia ' Department of Physical Metallurgy and Physics of Strength, The National University of Science and Technology "MISIS", Leninsky pr. 4, 119049 Moscow, Russia ' Department of Physical Metallurgy and Physics of Strength, The National University of Science and Technology "MISIS", Leninsky pr. 4, 119049 Moscow, Russia ' Department of Physical Metallurgy and Physics of Strength, The National University of Science and Technology "MISIS", Leninsky pr. 4, 119049 Moscow, Russia

Abstract: The purpose of this work is to study the processes of static tension deformation and fracture of nitrided sheet samples of 08Kh17T (type AISI 439) and 15Kh25T (type AISI 446) steels using the acoustic emission method. The nitriding was performed with pure nitrogen, at T = 1000-1100°C. Nitriding followed by annealing at 675ºC leads to the formation of the nitrogen ferrite structure with the Cr2N type precipitation and decreasing of the grain size across the full cross-section of both steel specimens. In spite of the significant strengthening, the nitrided specimens fail mostly by the ductile or quasi-ductile mechanism. The number of the brittle fracture elements in the fractures of the 15Kh25T steel is higher than in the 08Kh17T steel. Crack nucleation on large particles is a cause of the plastic flow stability loss in 15Kh25T steel in the nitrided state.

Keywords: corrosion-resistant ferritic steel; high-temperature nitriding; tensile test; acoustic emission; deformation; fracture; strain hardening exponent.

DOI: 10.1504/IJMMP.2017.091104

International Journal of Microstructure and Materials Properties, 2017 Vol.12 No.3/4, pp.183 - 192

Received: 24 May 2017
Accepted: 19 Jul 2017

Published online: 03 Apr 2018 *

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