Microstructure and mechanical properties of a multilayered CoCrNi/Ti coating with varying crystal structure
Date
2018
Authors
Cao, F.
Munroe, P.
Zhou, Z.
Xie, Z.
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Journal Title
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Journal article
Citation
Surface and Coatings Technology, 2018; 350:596-602
Statement of Responsibility
Fuyang Cao, Paul Munroe, Zhifeng Zhou, Zonghan Xie
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Abstract
Medium entropy alloys (MEAs), such as CoCrNi, have been demonstrated to combine high hardness and excellent ductility, thereby outperforming many high entropy alloys reported to date. In this study, a multilayered CoCrNi/Ti coating was deposited onto a M2 steel substrate using a DC magnetron sputtering system. Columnar grains can be observed in both the CoCrNi and Ti layers. A high density of periodic twin boundaries, aligned in a direction normal to the growth direction, was also observed within the columnar CoCrNi grains. Moreover, different crystal structures were identified for different CoCrNi layers. The outermost CoCrNi layer exhibited a FCC structure, whilst in contrast, both the middle and bottom CoCrNi layers exhibited a BCC structure. It was assumed that Shockley partial dislocations were responsible for the FCC to BCC transition occurring in both the bottom and middle CoCrNi layers. A high hardness of ~7.6 GPa and elastic modulus of ~233 GPa were determined for this multilayered coating by nanoindentation testing. Further, extraordinary damage tolerance was found in the multilayered CoCrNi/Ti coating under indentation loading. The steady shear banding behaviour during deformation may benefit energy dissipation and promote structural plasticity.
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Dissertation Note
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Available online 20 July 2018
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© 2018 Elsevier B.V. All rights reserved.