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Volume 156, 2012
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Why can TiAlCrSiYN-based adaptive coatings deliver exceptional performance under extreme frictional conditions?

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Abstract

Adaptive TiAlCrSiYN-based coatings show promise under the extreme tribological conditions of dry ultra-high-speed (500–700 m min−1) machining of hardened tool steels. During high speed machining, protective sapphire and mullite-like tribo-films form on the surface of TiAlCrSiYN-based coatings resulting in beneficial heat-redistribution in the cutting zone. XRD and HRTEM data show that the tribo-films act as a thermal barrier creating a strong thermal gradient. The data are consistent with the temperature decreasing from ∼1100–1200 °C at the outer surface to ∼600 °C at the tribo-film/coating interface. The mechanical properties of the multilayer TiAlCrSiYN/TiAlCrN coating were measured by high temperature nanoindentation. It retains relatively high hardness (21 GPa) at 600 °C. The nanomechanical properties of the underlying coating layer provide a stable low wear environment for the tribo-films to form and regenerate so it can sustain high temperatures under operation (600 °C). This combination of characteristics explains the high wear resistance of the multilayer TiAlCrSiYN/TiAlCrN coating under extreme operating conditions. TiAlCrSiYN and TiAlCrN monolayer coatings have a less effective combination of adaptability and mechanical characteristics and therefore lower tool life. The microstructural reasons for different optimum hardness and plasticity between monolayer and multilayer coatings are discussed.

  • This article is part of the themed collection: Tribology
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Publication details

The article was received on 21 Dec 2011, accepted on 02 Feb 2012 and first published on 03 Feb 2012


Article type: Paper
DOI: 10.1039/C2FD00131D
Faraday Discuss., 2012,156, 267-277

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    Why can TiAlCrSiYN-based adaptive coatings deliver exceptional performance under extreme frictional conditions?

    B. D. Beake, G. S. Fox-Rabinovich, Y. Losset, K. Yamamoto, M. H. Agguire, S. C. Veldhuis, J. L. Endrino and A. I. Kovalev, Faraday Discuss., 2012, 156, 267
    DOI: 10.1039/C2FD00131D

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