TEM investigations of active screen plasma nitrided Ti6Al4V and Ti6Al7Nb alloys

Krzysztof Szymkiewicz , Jerzy Morgiel , Łukasz Maj , Małgorzata Pomorska , Michał Tarnowski , Tadeusz Wierzchoń

Abstract

Direct current plasma nitriding (DC PN) helped to lower processing temperature as compared gas nitriding (GN) allowing to protect the surface with a layer of TiN compound and preserve the mechanical properties of the core material, which otherwise might lose its fine grain microstructure. However, samples of more complicated shapes are subjected to edge effects resulting in their overheating and uneven coverage. Introduction of active screen plasma nitriding (AS PN) should take care of both of these disadvantages, but the understanding on its effect on the compound and diffusive layers of processed parts is far from being clear. The present experiment was aimed at comparing the microstructure and the phase composition of DC PN and AS PN treated Ti6Al4V and Ti6Al7Nb alloys at temperatures of 680 °C and 740 °C. The microstructure investigations were performed with TEM/EDS methods, while phase analysis relied on electron diffraction indexing. It showed that switching from DC PN to AS PN resulted in covering it with a compact TiN layer backed with α″-Ti(N) martensite and Ti3Al-type layers, i.e. same as in the former case (DC PN) except the missing δ′-Ti2N layer. Additionally, it changes nitriding mechanism from absorption-diffusion of nitrogen ions to adsorption-diffusion of these species, what is a reason of slowing down of the rate of nucleation and growth of both the compound and diffusive layers. The growth of β-Ti(N) layer, which changes on cooling to α″-Ti(N) is controlled by in-diffusion of nitrogen to its front.

Author Krzysztof Szymkiewicz - Instytut Metalurgii i Inżynierii Materiałowej im. Aleksandra Krupkowskiego Polskiej Akademii Nauk (IMIM) [Polish Academy of Sciences (PAN)]
Krzysztof Szymkiewicz,,
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, Jerzy Morgiel - Instytut Metalurgii i Inżynierii Materiałowej im. Aleksandra Krupkowskiego Polskiej Akademii Nauk (IMIM) [Polish Academy of Sciences (PAN)]
Jerzy Morgiel,,
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, Łukasz Maj - Instytut Metalurgii i Inżynierii Materiałowej im. Aleksandra Krupkowskiego Polskiej Akademii Nauk (IMIM) [Polish Academy of Sciences (PAN)]
Łukasz Maj,,
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, Małgorzata Pomorska - [Instytut Metalurgii i Inzynierii Materialowej Polskiej Akademii Nauk]
Małgorzata Pomorska,,
-
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, Michał Tarnowski (FMSE / DSE)
Michał Tarnowski,,
- Division of Surface Engineering
, Tadeusz Wierzchoń (FMSE / DSE)
Tadeusz Wierzchoń,,
- Division of Surface Engineering
Journal seriesSurface and Coatings Technology, [Surface and Coatings Technology], ISSN 0257-8972
Issue year2020
Vol383
Pages1-8
Publication size in sheets0.5
Keywords in EnglishPlasma nitriding; Active screen; Ti6Al4V; Ti6Al7Nb; TEM
ASJC Classification1600 General Chemistry; 2505 Materials Chemistry; 2508 Surfaces, Coatings and Films; 3104 Condensed Matter Physics; 3110 Surfaces and Interfaces
DOIDOI:10.1016/j.surfcoat.2019.125268
URL https://www.sciencedirect.com/science/article/pii/S0257897219312587
Languageen angielski
File
1-s2.0-S0257897219312587-main.pdf 2.15 MB
Score (nominal)100
Score sourcejournalList
ScoreMinisterial score = 100.0, 23-07-2020, ArticleFromJournal
Publication indicators Scopus Citations = 1; Scopus SNIP (Source Normalised Impact per Paper): 2016 = 1.359; WoS Impact Factor: 2018 = 3.192 (2) - 2018=3.11 (5)
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