POTENTIALS OF NIOBIUM CARBIDE (NBC) AS CUTTING TOOLS AND FOR WEAR PROTECTION

摘要

The existence of different pseudo-cubic phases beside NbC, like Nb_4C_3, Nb_4C_5, define a large range of homogeneity of NbC_x (0.75≤x ≤1.0) in the binary phase diagram and enable a large process window. Properties, like micro-hardness, hot hardness, sliding wear resistance, elastic modulus and toughness can be tailored by theC/Nb ratio, the addition of secondary carbides and the type of binder. The initial NbC grade was substoichiometric, SPS sintered and cobalt bonded (NbC_(0.88)-12Co SPS). So far, NbC and Nb_20_5 do not have a REACH (Registration, Evaluation, Authorisation and Restriction of Chemical substances programme) classification related to human toxicology and are not listed as substances of very high concern contrary to WO_3 and C0_3O_4-. The NiMo-bonded stoichiometric NbC_(1.0)grades enable the substitution of cobalt by nickel, SPS by conventional sintering and NbC_(0.88) by NbC_(1.0) in view of functional properties. Nickel bonded NbC grades have improved toughness versus cobalt bonded NbC grades, but exhibit lower hardness. NiMo and NiM0_2C bonded NbCi.o grades compensated for the loss in hardness while keeping the toughness.