Microstructure and load bearing capacity of TiN/NbN superlattice coatings deposited on medical grade CoCrMo alloy by HIPIMS

Papken Ehiasar Hovsepian; Arunprabhu Arunachalam Sugumaran; Mark Rainforth; Jiahui Qi; Imran Khan; Arutiun Papken Ehiasarian

doi:10.1016/j.jmbbm.2022.105267

Microstructure and load bearing capacity of TiN/NbN superlattice coatings deposited on medical grade CoCrMo alloy by HIPIMS

J Mech Behav Biomed Mater. 2022 Aug:132:105267. doi: 10.1016/j.jmbbm.2022.105267. Epub 2022 May 10.

Authors

Papken Ehiasar Hovsepian¹, Arunprabhu Arunachalam Sugumaran², Mark Rainforth³, Jiahui Qi³, Imran Khan⁴, Arutiun Papken Ehiasarian²

Affiliations

¹ National HIPIMS Technology Centre, Materials and Engineering Research Institute, Sheffield Hallam University, United Kingdom. Electronic address: p.hovsepian@shu.ac.uk.
² National HIPIMS Technology Centre, Materials and Engineering Research Institute, Sheffield Hallam University, United Kingdom.
³ University of Sheffield, Mappin Street, Sheffield, United Kingdom.
⁴ Zimmer-Biomet UK Limited, Dorcan Industrial Estate, Swindon, United Kingdom.

PMID: 35569291
DOI: 10.1016/j.jmbbm.2022.105267

Abstract

In recent years significant progress has been made in the application of various ceramic, namely Metal nitride (MeN) functional coatings to engineer the surfaces of medical implants utilising metal-on-metal (MoM) articulation. This article reports on the load bearing capacity and structural response of TiN/NbN superlattice coatings deposited on medical grade CoCrMo alloy substrate under the application of localised load and the subsequent crack formation mechanism. The coatings have been deposited by mixed High Power Impulse Magnetron Sputtering-Unbalanced Magnetron Sputtering (HIPIMS-UBM) process. In the case of TiN/NbN coating deposited on CoCrMo substrate where E_coating/E_substrate is as high as 1.81 indicating that the substrate does not provide the necessary load bearing support for the brittle thin film, the utilisation of the Berkovich indentation technique proved to be a potent approach to study coating material as well as structural response to applied concentrated load. FIB/SEM analyses of the indented coatings revealed that in the hard-on-soft material systems cracks will initiate due to sub-coating substrate deformation and then propagate towards the coating surface. The FIB/SEM and low magnification XTEM analysis showed that an exceptionally strong TiN/NbN coating substrate adhesion bonding was achieved due to the utilisation of the HIPIMS pre-treatment. High resolution XTEM analyses revealed, for the first time, that during the indentation a collective rotation and alignment of the individual layers of the superlattice stack takes place without compromising coatings integrity which is clear evidence for the exeptionally high coating fracture toughness. The high toughness of the superlattice structured TiN/NbN coatings combined with their exceptionally high adhesion on madical grade CoCrMo ranks them as a strong candidate for medical implant applications.

Keywords: Crack initiation; High power impulse magnetron sputtering; Medical implants; Superlattice coating; Toughness.

MeSH terms

Alloys* / chemistry
Coated Materials, Biocompatible / chemistry
Materials Testing
Metals
Nuclear Proteins
Surface Properties
Weight-Bearing

Substances

Alloys
Coated Materials, Biocompatible
Metals
Nuclear Proteins