Titanium-molybdenum-carbon-nitrogen

In many of the transition metals, such as titanium, vanadium and molybdenum, carbon, nitrogen and oxygen atoms can fit into octahedral holes, and hydrogen into the teualredral holes. The fit here is estimated by assuming the atoms all have incompressible radii, and die contact must be such tlrat tire interstitial atoms do not rattle around in the holes. 

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

Interstitial alloys form when small nomnetallic atoms fit within the octahedral or tetrahedral holes of the crystalline lattice of the metal. The formulas for these alloys depend both on the type of hole occupied by the nomnetallic atom and on the fraction of holes occupied. For example, titanium and carbon form an alloy with a closest-packed structure for titanium in which all of the octahedral holes are filled with carbon atoms. Since the number of octahedral holes in a closest-packed structure is equal to the number of atoms in the structure, the ratio of carbon atoms to titanium atoms must be 1 1 and the corresponding formula is TiC. In the compound formed between molybdenum and nitrogen, by contrast, only one-half of the octahedral holes in the closest-packed structure of Mo are filled with N. Therefore, the formula for this compound is M02N. Table 23.3 lists the formulas and relative number of holes filled for several different interstitial alloys. 

Stainless steels are alloys of iron with a low carbon content (usually < 2%) and a minimum of 10.5% chromium. Dependant on the grade, stainless steels can also contain nickel, manganese, molybdenum, titanium, copper and nitrogen. These other alloying elements are used to enhance properties such as formability, strength and cryogenic toughness. The main requirement for stainless steels is that they should be corrosion resistant for a specified application or environment. 

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. 

Residual Elements. In addition to carbon, manganese, phosphoms, sulfur, and silicon which are always present, carbon steels may contain small amounts of hydrogen, oxygen, or nitrogen, introduced during the steelmaking process nickel, copper, molybdenum, chromium, and tin, which may be present in the scrap and aluminum, titanium, vanadium, or zirconium, which may have been introduced during deoxidation. 

The compacted powder mixtures of these materials are usually liquid phase sintered with Ni or Ni-Co binder metal alloys. The microstracture features a core-and-rim stracture of the hard phase with a molybdenum- and carbon-rich (Ti,Mo)C rim and a titanium- and nitrogen-rich Ti(C,N) core. This microstructure can be made visible in the SEM (Figure 16). The metallurgy of the phase reactions is not... 

Emission spectroscopy with arc and spark excitation has been used since the 1930s for many industrial analyses. In metaUurgy, for example, the presence in iron and steel of the elements nickel, chromium, sihcon, manganese, molybdenum, copper, aluminum, arsenic, tin, cobalt, vanadium, lead, titanium, phosphoms, and bismuth have been determined on a routine basis. Modem instruments can also measure oxygen, nitrogen, and carbon in metals, which used to require separate measurements with dedicated high-temperature... 

The Mo-Cr stainless steels of controlled purity, described earlier, although in some instances containing more than 0.01% C, are immune to intergranular corrosion. This is accounted for by their molybdenum content, which slows down diffusion of carbon and nitrogen, and by their titanium or niobium content which, if present, reacts preferentially with carbon and nitrogen. 

Alloying additions of chromium, nickel, molybdenum, increase the pitting resistance, whereas silicon, sulfur, carbon and nitrogen, decrease the resistance to pitting. Addition of titanium increase resistance of steels only in solutions of FeCl3 and not in other mediums. 

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