The effects of thermal conductivity and anisotropy on the electro discharge machinability of ceramics containing graphene platelets

Abstract

In this study, the electro discharge machinability of spark plasma sintered ceramics such as AlN and SiAlON, which achieves almost the same electrical conductivity level with the addition of GPLs, were comparatively investigated depending on anisotropic thermal and electrical conductivity. The lower thermal conductivity of both materials in the through-plane direction than in-plane direction led to higher surface roughness and material removal rates in the through-plane direction machining. Similarly, the lower thermal conductivity of GPLs-SiAlON than GLPs-AlN in both machining directions resulted in rougher machined surfaces and slightly higher material removal rate values. Due to the generation of the strong spark, higher material removal rate but lower surface quality obtained at high pulse current compared to low pulse current. Microstructures and EDS-SEM analyzes showed that melting + evaporation and oxidation + decomposition were effective material removal mechanisms. Through-plane direction processing was suitable when a high material removal rate was required, while in-plane direction processing could be preferred for good machining surface quality.