Fabrication and Mechanical Properties of Al₂O₃-BN/TiC/Ni FGMs

Abstract

Symmetrically graded materials of the Al₂O₃-BN/TiC/Ni were fabricated by SHS/HIP. High residual compressive stresses were produced in the outer layer due to the thermal expansion mismatch between the outer Al₂O₃-BN ceramic and the inner TiC/Ni cermet layer. The dispersion of BN in the Al₂O₃ layer increased the residual stress to higher levels than that induced in the Al₂O₃/TiC/Ni system. The BN has the layer structure with cleavage faces. The tribological properties of the outer Al₂O₃-BN layer were investigated at room temperature and 500°C in air. The friction coefficient of the outer layer was lower than that of monolithic Al₂O₃, especially at 500°C. The residual compressive stress was found to improve wear resistance of the surface layer.