Powder Metallurgy Processing of TiC-FeCrMo Cermets: Sintering and Thermal Treatments

Densification of TiC-FeCrMo cermets by vacuum sintering increases as the pressure of the furnace chamber decreases. This is due to a more efficient reduction of powder oxides. Ar injection above 1300ºC avoids iron evaporation. However, some gas is entrapped leaving residual porosity after sintering. High carbon contents lead to precipitation of undesired M7C3 carbides at the (Ti1-x,Mox)yCz - metal interface and the formation of retained austenite. Continuous cooling experiments prove that TiC-FeCrMo cermets are suitable for air-quenching, simplifying their fabrication. The bainitic transformation is sensitive to the carbon content of the matrix. These materials exhibit complex microstructures consisting of TiC grains in a matrix comprised of martensite, ferritic bainite, M7C3 and M23C6 carbides. TiC-FeCrMo cermets with optimum heat treatments present a combination of hardness, strength and toughness in the range of those reported for WC-Co cemented carbides used as roller guides in hot rolling applications.