Effect of Graphite Microstructure on their Physical Parameters and Wettability Properties

To produce castings of titanium, nickel, zinc, copper and many other metal alloys, graphite molds can be used. Using graphite molds has many advantages, including that no lubricate or coating layers are needed, a high cooling rate, and ease of production of complex shapes. However, for high quality castings, high quality graphite is required with high mechanical properties and a high heat transfer coefficient. Since there is no room for adjusting the chemical composition of graphite molds, the most important factor determining the properties of the molds is their production process. Thus, in the present study, mechanical properties of two different types of graphite are investigated. The two types of graphite were produced by different technological processes: a typical process of graphite production from isotropic coke, and an electrolytic method of production. The research included mechanical testing and structural investigation by scanning electron microscopy. Chemical analysis was performed by Energy Dispersive x-ray Spectroscopy, and x-ray phase analysis was performed by XRD. Mechanical properties were determined by compression and three-point flexural testing at room temperature. It was found that the porosity of graphite is the key parameter determining its mechanical properties. In addition, it was found that mechanical anisotropy of graphite is dependent on the production method where the size and distribution of pores play an important role.