Iron nitride containing

Figure 8.8 Structure of FeWN2. An example of a ternary transition metal nitride containing octahedral iron and trigonal prismatic tungsten. Small white = Iron, Black = Tungsten, Large...

Figure 8.1 Structure of Li,, FcN2. An example of a lithium-containing ternary nitride containing FeN2 chains. Gray = Lithium, Black = Iron, White = Nitrogen.

Iron nitride, Fe4N, has a ccp arrangement of Fe atoms with an N atom at the center of the face-centered cube (see Figure 5.57). The cubic cell contains one molecule, a0 = 3.7885 A. This places N in an octahedral layer. It fills one-half of sites in alternate O layers. The packing layer sequence is more complicated than the simple figure ... 

Mossbauer spectroscopy may be applied to compounds containing iron. Some limited data have been reported for the iron nitride and related iron carbide clusters.355 358365... 

There are numerous /i4-carbide- and nitride-containing clusters examples from the iron-triad include [M4C(CO)i3] (M = Fe, and [M4N(CO)i2] (M = Fe,... 

Steel is an alloy of iron. The production of iron from its ore is a chemical reduction process that results in a crude iron containing many undesired impurities. Iron from a blast furnace typically contains 0.6 to 1.2% silicon, 0.4 to 2.0% manganese, and lesser amounts of phosphorus and sulfur. In addition, there is considerable dissolved carbon. In the production of steel these impurity elements are removed by oxidation in a vessel called a converter. In modem steelmaking, the oxidizing agent is either pure O2 or O2 diluted with argon. Air cannot be used directly as the source of O2 because N2 reacts with the molten iron to form iron nitride, which causes the steel to become brittle. 

The case structure of nitiided steel depends on its type, concentration of alloying elements and particular conditions of nitiiding treatment. The diffusion zone is the original core microstructure with the addition of nitride precipitates and nitrogen solid solution. The surface compoxmd zone is the region where y (Fe4N) and e (Fe2-3N) intermetallics are formed. The corrosion resistance of steel varies with nitrided layer structure. The surface "white layer" can contain e nitride, y nitride or a two phase mixture e+y, below that is the diffusion zone. In add solutions the iron nitrides corrode more slowly than iron and when the "white zone" is formed on the steel surface the improvement of the corrosion resistance is a fact. In Fig. 1 is shown the typacal structure of nitrided plain carbon steel (Minkevich, 1965). 

Wad] Wada, H., Pehike, R.D., Nitrogen Solubility and Aluminium Nitride Precipitation in Liquid Iron Alloys containing Nickel and Aluminum , Metall Trans. B, lOB, 409-412 (1979) (Phase Diagram, Phase Relations, Thermodyn., Experimental,, 4)... 

Typically, Be-containing alloys and intermetallic phases have been prepared in beryllia or alumina crucibles Mg-containing products have been synthesized in graphite, magnesia or alumina crucibles. Alloys and compounds containing Ca, Sr and Ba have been synthesized in alumina , boron nitride, zircon, molybdenum, iron , or steel crucibles. Both zircon and molybdenum are satisfactory only for alloys with low group-IIA metal content and are replaced by boron nitride and iron, respectively, for group-IIA metal-rich systems . Crucibles are sealed in silica, quartz, iron or steel vessels, usually under either vacuum or purified inert cover gas in a few cases, the samples were melted under a halide flux . 

Burnishing is the formation of black-brown oxide films on iron and its alloys by controlled oxidation of cleaned metal surfaces. These films are extremely complex and contain, in addition to maghemite and magnetite (or a substituted magnetite for Ni, Mo or Co alloys), various nitride phases - Fe4N, FeaN and FeN. The nitride phases are adjacent to the metal and the iron oxides are in the outer layers of the film (Gebhardt, 1973). 

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