Analysis of Wire-EDM finishing cuts on large scale ZrO2-TiN hybrid spark plasma sintered blanks

Technical ceramics have numerous application in the industrial and biomedical field because of material properties such as: high hardness, high Young’s modulus, chemical resistance and dimensional stability. These superior properties make it difficult to shape technical ceramics in a flexible and accurate way. By embedding an electrically conductive phase inside tough, hard and brittle non-conductive technical ceramics, e.g.: ZrO2, Al2O3 & SiC, it is possible to create ceramic blanks which can be processed by electro-chemical processes, such as Wire Electrical Discharge Machining (W-EDM). Till today, research on EDM machining of ceramic parts is often limited to the machining of small sized samples, mainly due to the fact that larger blanks are difficult to produce or not commercially available. Today, novel sintering techniques make it possible to create large fully dense ceramic composite blanks, allowing the production of bigger monolithic ceramic parts in a more cost effective manner. In the presented research, the effect of higher cutting dimensions on the Wire EDM performance is investigated. ZrO2-TiN blanks (diameter: 250 mm, height: 16 mm) made by hybrid plasma spark sintering are processed by W-EDM. Different finishing steps are used to obtain Ra roughness values below 0.5 μm, and for each finishing step a detailed analysis is made of the surface characteristics and material removal mechanism. The surface quality and material removal mechanisms are compared to findings in literature for small scale blanks. Beside melting and evaporation, other phenomena such as chemical decomposition and recast layers can be observed. Furthermore the effect of the finishing cuts on the bending strength is tested using 4 point bending setup and correlated to the surface roughness. Analysis from this research show that large scale ZrO2-TiN blanks are industry ready to be machined by W-EDM, hopefully bringing forward new applications.status: publishe