TiN-Nanoparticulate-Reinforced ZrO2 for Electrical Discharge Machining

Abstract

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.

Research on the influence of the discharge breakdown process on the crater formation during EDM

“…A copper of 1 mm in diameter was selected as the tool and die steel was selected as the workpiece. The working liquid was kerosene, and the positive polarity was applied (Lazar et al , 2019). The workpiece surface needs to be polished to remove its oxide layer before the experiment, as shown in Figure 19(b).…”

Enhanced Mechanical Properties of Yellow ZrN Ceramic with Addition of Solid Solution of TiN

“…They found that the relative density and Vickers hardness of the samples were improved when TiN was used as a sintering additive. Titanium nitride (TiN) demonstrated outstanding mechanical properties, such as high hardness, excellent chemical stability, and a high melting point [ 8 , 9 ]. Additionally, ZrN and TiN crystallize in the face-centered cubic (fcc) structure, resulting in the formation of solid solutions during the sintering process [ 10 ].…”

Microstructure and Properties of ZrO2-AlN Composite Ceramics by Microwave Sintering

“…Composite materials are expected to overcome the inherent shortcomings of single-phase ceramics and bring about an overall improvement in structure and functional characteristics [9][10][11] . For example, Al2O3-ZrO2 system [12] is one of the most studied and promising ceramic composites.…”