Reduced anisotropic properties of Cold Isostatic Pressed graphite matrix compacts

Abstract

Matrix graphite (MG) compacts were produced by conventional uniaxial pressing (UP) and Cold Isostatic Pressing (CIP). An additional premolding procedure with UP was also carried out before CIP to manufacture MG compacts with a cylinderical shape which was not achievable using CIP alone. It was noted that the MG compacts made by CIP revealed more isotropic microstructural and thermal properties compared to the MG compacts made by UP. The MG compacts made by UP had graphite grains aligned in the transverse direction and severe anisotropic thermal expansion and conductivity according to direction of orientation (axial and transverse). On the other hand, the MG compacts made by CIP showed randomly aligned graphite grains, almost identical linear thermal expansion and shrinkage behaviors, and a reduced thermal conductivity difference between the axial and transverse directions compared to that of the UP MG compacts. The properties of the premolded CIP MG compacts also revealed considerable anisotropic properties. Finally, three-point bending experiments showed that the MG compacts made by CIP obtained 230% higher fracture toughness to the transverse direction compared to that of the UP MG compacts.