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Open AccessFeature PaperArticle

TiN-Nanoparticulate-Reinforced ZrO2 for Electrical Discharge Machining

1
Department for Nanostructured Materials, Jožef Stefan Institute, 1000 Ljubljana, Slovenia
2
Jožef Stefan International Postgraduate School, 1000 Ljubljana, Slovenia
3
Max-Planck-Institut for Iron Research, Max-Planck Straße 1, 40237 Düsseldorf, Germany
*
Author to whom correspondence should be addressed.
Materials 2019, 12(17), 2789; https://doi.org/10.3390/ma12172789
Received: 19 July 2019 / Revised: 26 August 2019 / Accepted: 27 August 2019 / Published: 30 August 2019
(This article belongs to the Special Issue Mechanical Properties and Applications of Advanced Ceramics)
This study presents a fabrication route for an electrically conductive ZrO2–TiN ceramic nanocomposite with a nanoscale TiN phase occupying ≤30 vol% to improve the mechanical reinforcement of the zirconia matrix, and at the same time provide electrical conductivity to facilitate electro-discharge machining (EDM). The TiN nanoparticles were incorporated into a 3 mol% yttria-stabilized tetragonal zirconia (Y-TZP) powder, either by admixing a TiN nanopowder (MCP) or by using in-situ synthesis (ISS) via the forced hydrolysis of a titanyl sulphate aqueous solution and the direct nitriding of as-synthesized titania nanoparticles, followed by consolidation and rapid sintering in a spark plasma sintering (SPS) system. The initial phase composition and crystal structure of the as-synthesized powders and the sintered samples were characterized by transmission electron microscopy (TEM) and X-ray difraction (XRD). The influence of the different fabrication routes on the microstructural evolution, electrical and mechanical properties, and affinity for EDM were assessed using TEM, focused ion beam scanning electron microscopy (FIB-SEM, Vickers indentation, electrical conductivity measurements, and profilometry. The MCP synthesis route resulted in finer microstructures that are less prone to microstructural inhomogeneities; however, using the ISS route, it was possible to fabricate electrically conductive Y-TZP nanocomposites containing only 15 vol% of the TiN nanoparticulate phase. Both synthesis routes resulted in an increase of the fracture toughness with an increase of the TiN phase due to the nanoparticulate TiN reinforcement of the Y-TZP ceramic matrix via crack-bridging toughening mechanisms. As both synthesis routes yielded Y-TZP nanocomposites capable of successful EDM machining at a TiN content of ≥30 vol% for the MCP and ≥ 15 vol% TiN for the ISS, a possible mechanism was developed based on the microstructure evolution and grain growth. View Full-Text
Keywords: zirconia; titanium nitride; spark plasma sintering; nanocomposite; mechanical properties; electrical conductivity; electrical discharge machining zirconia; titanium nitride; spark plasma sintering; nanocomposite; mechanical properties; electrical conductivity; electrical discharge machining
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MDPI and ACS Style

Lazar, A.; Kosmač, T.; Zavašnik, J.; Abram, A.; Kocjan, A. TiN-Nanoparticulate-Reinforced ZrO2 for Electrical Discharge Machining. Materials 2019, 12, 2789.

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