Low-Temperature Decomposition of the (Nb,W)C Carbide Solid Solutions in NbC–WC–Cu Composite Alloys

—NbC–WC–Cu composite alloys are fabricated at 1300°C by impregnating mixtures of compacted and noncompacted carbide powders with the copper melt under low-frequency (80 Hz) vibration. Under these conditions, carbides are shown to interact with the formation of core (NbC)–shell ((W,Nb)C) solid solution) structures in the copper melt. The formation of a (W,Nb)C solid solution on the surface of NbC particles promotes the wetting of the carbide with copper. The thermal stability of the carbide solid solutions is investigated during isothermal holding at 500 and 1000°C for 60 min and during slow (10 K/min) heating to 1300°C. A reversible decomposition is detected, and the boundaries of low-temperature latent decomposition of the (Nb,W)C solid solutions are determined by the mass ratio of monocarbides NbC : WC in their alloy with copper. The higher the ratio, the lower the (Nb,W)C decomposition temperature.