Abstract
An NbC–Fe composite powder was synthesized from an Nb2O5/Fe/C mixture by electrochemical reduction and subsequent carbonization in molten CaCl2–NaCl. The composite has a core–shell structure, in which NbC acts as the cores distributing in the Fe matrix. A strong bonding between NbC and Fe is benefit from the core–shell structure. The sintering and electrochemical reduction processes were investigated to probe the mechanism for the reactions. The results show that NbC particles about several nanometers were embraced by the Fe shell to form a composite about 100 nm in size. This featured structure can feasibly improve the wettability and sinterability of NbC as well as the uniform distribution of the carbide in the cast steel. By adding the composite into steel in the casting process, the grain size of the casted steel was markedly deceased from 1 mm to 500 μm on average, favoring the hardening of the casted steel.
Highlights
Niobium carbide (NbC) is a non-oxide ceramic material that has been widely used as cutting tools, protective coating for instruments, structural materials, magnetic and electric components because of its excellent chemical and physical properties, such as high melting point (3610 ◦ C), good thermal stability, chemical inertness, low friction coefficient and high hardness (1800 HV) [1,2,3,4].In particular, NbC powder is used as an additive into other metals or alloys to strengthen the mechanical properties of these materials [4,5,6,7]
Phase composition of the obtained sample was determined via a D/Max-2500PC X-ray diffractometer (XRD) with Cu Kα radiation, and the morphology and structure were characterized via a JSM-6360L V scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDS) and a JEM-2010 transmission electron microscope (TEM)
The predominant appearance of Fe(NbO3)2 implies the existence of Fe2O3 in the Fe source, and chemical reaction appearance of Fe(NbO
Summary
Niobium carbide (NbC) is a non-oxide ceramic material that has been widely used as cutting tools, protective coating for instruments, structural materials, magnetic and electric components because of its excellent chemical and physical properties, such as high melting point (3610 ◦ C), good thermal stability, chemical inertness, low friction coefficient and high hardness (1800 HV) [1,2,3,4]. NbC powder is used as an additive into other metals or alloys to strengthen the mechanical properties of these materials [4,5,6,7]. The composites consisting of metal and ceramic particle reinforcements play an essential role in the production of cost-competitive and environment-friendly materials [8,9,10]. It has been pointed out that the insufficient characteristics of individual carbides can be modified if they are backed by a relatively ductile metal prior to acting as an additive [18], since few challenges exist for the mutual dissolution between metals
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