Sialon ceramic with gradient microstructures

In order to combine the high hardness of alpha-Sialon and high toughness of beta-Sialon, a graded Sialon ceramic was developed in this work. The microstructures and the properties of the graded Sialon ceramic change gradually from spherical alpha-Sialon grains on the surface (HV10 = 19 GPa, HV0.1 = 34 GPa. and K-1c = 4.3 MPam(1/2)) to elongated beta-Sialon grains in the inner core (HV10 = 15.7 GPa, HV0.1 = 24 GPa and K-1c = 7.3 MPam(1/2)). Mixtures of the alpha-Sialon grains and the beta-Sialon grains were observed in the transitional zone with hardness HV0.1 = 24 similar to 30 GPa. The graded Sialon ceramic was produced in situ by using a green compact starting from a homogeneously mixed powder mixture. (C) 1998 Elsevier Science S.A.