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Title: Magnetic layer formation on plasma nitrided CoCrMo alloy
Authors: Öztürk, Orhan
Okur, Salih
Pichon, L.
Liedke, M. O.
Riviere, Jean Paul
Keywords: CoCrMo alloy
Expanded austenite structure
Plasma nitriding
Issue Date: Jul-2011
Publisher: Elsevier Ltd.
Source: Öztürk, O., Okur, S., Pichon, L., Liedke, M.O., and Riviere, J.P. (2011). Magnetic layer formation on plasma nitrided CoCrMo alloy. Surface and Coatings Technology, 205(SUPPL. 2), S280-S285. doi:10.1016/j.surfcoat.2011.01.047
Abstract: In this study structural and magnetic character of the expanded austenite phase (γN) layer formed on a medical grade CoCrMo alloy by a low-pressure Radio-Frequency plasma nitriding process was investigated. The formation of the expanded austenite phase is facilitated at a substrate temperature near 400°C for 1, 2, 4, 6 and 20h under a gas mixture of 60% N2-40% H2. The magnetic state of the γN layers was determined by a surface sensitive technique, magneto-optic Kerr effect (MOKE), and with a scanning probe microscope in magnetic force mode (MFM). Strong evidence for the ferromagnetic nature of the γN-(Co,Cr,Mo) phase is provided by the observation of stripe domain structures and the hysteresis loops. The ferromagnetic state for the γN phase observed here is mainly linked to large lattice expansions (~10%) due to high N contents (~30at.%). As an interstitial impurity, nitrogen dilates the host lattice i.e. the Co-Co (or Fe-Fe) distance is increased, which strongly influences the magnetic interactions. An analogy between the magnetic properties of the expanded phases, γN-(Fe,Cr,Ni) and γN-(Co,Cr,Mo), formed in austenitic stainless steel alloys and the CoCrMo alloy of this study is made, and it is suggested that the ferromagnetic states for the γN-(Co,Cr,Mo) and γN-(Fe,Cr,Ni) phases may be correlated with the volume dependence of the magnetic properties of fcc-Co/Co4N and fcc-Fe/Fe4N, respectively.
ISSN: 0257-8972
Appears in Collections:Physics / Fizik
Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

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