Molybdenum nickel carbides

Fra] Fraker, A.C., Stadelmaier, H.H., The q Carbides of Molybdenum-Iron, Molybdenum-Cobalt and Molybdenum-Nickel , Trans. AIME, 245, 847-850 (1969) (Phase Diagram, Crys. Structure, Experimental, Morphology, 20)... 

Figure 7.17 contains the XRD pattern for the precursor molybdenum powder. Although the XRD pattern for the black powder in Figure 7.18 contained peaks for unreacted molybdenum that correspond to those in Figure 7.17, no unreacted nickel was detected. Molybdenum and nickel carbide peaks were both present. The XRD pattern of the light gray powder is shown in Figure 7.19. Although nickel and molybdenum carbides are again present, less unreacted molybdenum was present than in the black powder. The cause of reaction of molybdenum with the carbide powder in the presence of nickel is unclear. Recall that in the absence of nickel, molybdenum processed for 1 h reacted only minimally at the surface.

Tip-based oxidation experiments were first performed on Si(lll) and polycrystaline tantalum faces. - Since then a large number of materials have been locally oxidized, such as compound 111-V semiconductors silicon carbide several metals such as titanium, tantalum, aluminum, molybdenum, nickel, and niobium perovskite manganite thin films dielectrics such as silicon nitride... 

Catalytic activity of double molybdenum and nickel carbides and nickel-promoter molybdenum carbides... 

We performed three series of experiments to study the catalytic activity of double molybdenum and nickel carbides and nickel-promoter molybdenum carbides (Table 4.11.1 series A, B, C). 

Table 4.11.1 gives the products of the carbonization of molybdenum-nickel alloys synthesized under various conditions. The optimum carbonization conditions lead to the formation of M02C and double carbides rather than MoC, since it has a low catalytic activity. Figure 4.11.2 shows the XRD patterns of the coatings... 

We proposed a new two-stage method for synthesizing double molybdenum and nickel carbides and nickel-promoter molybdenum carbide. It consists in the electrochemical synthesis of molybdenum and nickel alloys in chloride melt followed by carbonization in a chloride-carbonate melt. 

Moissanite, see Silicon carbide Molybdenite, see Molybdenum disulfide Molybdite, see Molybdenum(VI) oxide Molysite, see Iron(III) chloride Montroydite, see Mercury(II) oxide Morenosite, see Nickel sulfate 7-water Mosaic gold, see Tin disulfide Muriatic acid, see Hydrogen chloride, aqueous solutions... 

Chrome—nickel alloy heating elements that commonly ate used in low temperature furnaces are not suitable above the very low end of the range. Elements commonly used as resistors are either silicon carbide, carbon, or high temperature metals, eg, molybdenum and tungsten. The latter impose stringent limitations on the atmosphere that must be maintained around the heating elements to prevent rapid element failure (3), or the furnace should be designed to allow easy, periodic replacement. 

Carbon content is usually about 0.15% but may be higher in bolting steels and hot-work die steels. Molybdenum content is usually between 0.5 and 1.5% it increases creep—mpture strength and prevents temper embrittlement at the higher chromium contents. In the modified steels, siUcon is added to improve oxidation resistance, titanium and vanadium to stabilize the carbides to higher temperatures, and nickel to reduce notch sensitivity. Most of the chromium—molybdenum steels are used in the aimealed or in the normalized and tempered condition some of the modified grades have better properties in the quench and tempered condition. 

AISI 321 and 347 are stainless steels that contain titanium and niobium iu order to stabilize the carbides (qv). These metals prevent iatergranular precipitation of carbides during service above 480°C, which can otherwise render the stainless steels susceptible to iatergranular corrosion. Grades such as AISI 316 and 317 contain 2—4% of molybdenum, which iacreases their creep—mpture strength appreciably. In the AISI 200 series, chromium—manganese austenitic stainless steels the nickel content is reduced iu comparison to the AISI 300 series. 

The physical and mechanical properties of steel depend on its microstmcture, that is, the nature, distribution, and amounts of its metaHographic constituents as distinct from its chemical composition. The amount and distribution of iron and iron carbide determine most of the properties, although most plain carbon steels also contain manganese, siUcon, phosphoms, sulfur, oxygen, and traces of nitrogen, hydrogen, and other chemical elements such as aluminum and copper. These elements may modify, to a certain extent, the main effects of iron and iron carbide, but the influence of iron carbide always predominates. This is tme even of medium alloy steels, which may contain considerable amounts of nickel, chromium, and molybdenum. 

Mechanical properties depend on the alloying elements. Addition of carbon to the cobalt base metal is the most effective. The carbon forms various carbide phases with the cobalt and the other alloying elements (see Carbides). The presence of carbide particles is controlled in part by such alloying elements such as chromium, nickel, titanium, manganese, tungsten, and molybdenum that are added during melting. The distribution of the carbide particles is controlled by heat treatment of the solidified alloy. 

Another type of nickel alloy with which problems of intergranular corrosion may be encountered is that based on Ni-Cr-Mo containing about 15% Cr and 15% Mo. In this type of alloy the nature of the grain boundary precipitation responsible for the phenomenon is more complex than in Ni-Cr-Fe alloys, and the precipitates that may form during unfavourable heat treatment are not confined to carbides but include at least one inter-metallic phase in addition. The phenomenon has been extensively studied in recent years . The grain boundary precipitates responsible are molybdenum-rich M C carbide and non-stoichiometric intermetallic ix... 

Properties of the deposits Almost any material which can be melted is suitable for plasma spraying, giving a vast range of possible coatings of single or mixed metallic or non-metallic substances. It is often possible to produce types of coatings which are not obtainable in any other way. Typical of the materials which are plasma sprayed are copper, nickel, tantalum, molybdenum. Stellites, alumina, zirconia, tungsten and boron carbides, and stainless steels. 

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