Molybdenum carbonitride

Nitrogen and carbon are the most potent solutes to obtain high strength in refractory metals (55). Particulady effective ate carbides and carbonitrides of hafnium in tungsten, niobium, and tantalum alloys, and carbides of titanium and zirconium in molybdenum alloys. 

Molybdenum carbide is also used in TiC—Ni-based alloys and in titanium carbonitride-based cermets for metal-cutting appHcations. 

In the polyacrylic synthetic fibre industry, carbonitrided molybdenum guides have been used in place of chromium plated steel because of their resistance to corrosion and erosion. Chemicals that attack molybdenum are listed in Table 5.9. 

The first carbonitride alloys based on Ti(C,N)—Ni—Mo were introduced in 1970 followed by (Ti, Mo)(C,N)-based compositions having fine microstructures that provided a balance of wear resistance and toughness (4). Continued research on the titanium carbonitride alloys, often called TiC—TiN cermets, in the 1980s led to the development of complex cermets having a variety of additives such as molybdenum carbide(2 1) [12069-89-5], Mo2C, TaC, NbC, zirconium carbide [12020-14-3], ZrC, hafnium carbide [12069-85-1], HfC, WC, vanadium carbide [12070-10-9], VC, chromium carbide (3 2)... 

The boundary between hardmetals and cermets is not strict because many of these compacts resemble microstructure features of both type of materials [106] faceted WC crystals together with round-shaped titanium carbonitride-based hard particles. Generally, these titaniiun carbonitride hardmetals are comparable with respect to properties and microstructure to WC-based hardmetals. The powders of these materials are liquid phase sintered with Ni or Ni-Co binder metal alloys. The core-and-rim structure of the hard phase usually exhibit a molybdenum- and carbon-rich (Ti,Mo)C rim and a titanium- and nitrogen-rich Ti(C,N) but can also be inverted (compare Fig. 26). The metallurgy of the phase reactions is (because of the complexity of the multicomponent system) not yet fully understood [69]. 

Typical cermet material is generally composed of titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), tantalum (Ta), nickel (Ni), cobalt (Co), tungsten carbide (WC), molybdenum (Mo), and vanadium (V). 

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