Mechanochemically synthesized NbC cermets: Part II. Mechanical properties

The mechanical behavior of mechanochemically synthesized NbC cermets was in vestigated. Material hardnesses range from a high of 19.6 GPa for as-synthe sized cermets containing about 4 vol% of Fe to a low of about 4 GPa for hea t-treated cermets containing about 34 vol% Cu. Higher hardness generally co rrelates with lower fracture toughness (about 2 MPa m(1/2) for cermets cont aining the highest percentage of NbC) and vice versa. Highest fracture toug hness (about 7.5 MPa m(1/2)) is found in NbC-18 vol% Fe cermets heat treate d extensively following consolidation. Abnormally low fracture toughnesses are found in high-Cu-content cermets in which Cu segregation takes place du ring heat treatment. Current models of ceramic toughening can be applied to describe the fracture behavior of NbC-Fe cermets.