Electrical Discharge Machining of SiAlON Ceramics Using Multifunctional Coatings and Assistive Powder

Producing complex-shaped products of oxynitrides is one of the biggest challenges of the modern industry. The machining of those ceramics encounters challenges in terms of their physical and mechanical properties, such as their high brittleness and insulating electric properties. The problem may be solved by assisted electrical discharge machining by depositing multifunctional coatings by a plasma vacuum method that can contribute to electrical conductivity of the ceramic surface to provide wear-resistant properties. And that is the original solution because other authors either prefer using monofunctional coatings to provide electrical conductivity on the ceramic surface. The study employed TiN and quatronitride (Ti,Al,Cr,Si)N coatings, which were deposited on SiAlON samples. The adhesion strength and wire electrical discharge machining tests revealed the most favorable option (TiN coating) that demonstrated better adhesion and less brittle behavior. In addition to multifunctional coating, it is proposed to combine it with assisting powder by adding it in the interelectrode gap. MgO and CoO powder suspension (150 g/L) and erosion product suspension were chosen for kerf production. The MgO suspension was produced based on mineral oil, taking into account the chemical properties of magnesium-containing substances. Other suspension options were produced based on deionized water.