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Cobalt aluminides

Calorised Coatings The nickel- and cobalt-base superalloys of gas turbine blades, which operate at high temperatures, have been protected by coatings produced by cementation. Without such protection, the presence of sulphur and vanadium from the fuel and chloride from flying over the sea promotes conditions that remove the protective oxides from these superalloys. Pack cementation with powdered aluminium produces nickel or cobalt aluminides on the surfaces of the blade aerofoils. The need for overlay coatings containing yttrium have been necessary in recent times to deal with more aggressive hot corrosion conditions. [Pg.477]

Pack cementation is the most widely used process for making diffusion aluminide coatings. Diffusion coatings are primarily aluminide coatings composed of aluminum and the base metal. A nickel-based superalloy forms a nickel-aluminide, which is a chemical compound with the formula NiAl. A cobalt-based superalloy forms a cobalt-aluminide, which is a chemical compoimd with the formula CoAl. It is common to incorporate platinum into the coating to improve the corrosion and oxidation resistance. This is called a platinum-aluminide coating. Diffusion chrome coatings are also available. [Pg.792]

Reactive Sputtering. Nanocomposite films of Ni3N/AlN, CoN/BN, and CoN/ Si3N4 were synthesized by reactive sputtering of a nickel aluminide, a cobalt boride,... [Pg.416]

In order to improve the wear resistance of machining tools made of hard metals, steel, tungsten carbide cobalt, titanium aluminide, titanium and silicon substrates have been coated with SiBNsC via CVD of TABB [107, 108]. Layers produced in this fashion are dense and exhibit a Vickers hardness of 1000-2300 kg mm S depending on the specific process parameters. [Pg.169]

Very interesting are the results of recent investigations on the mechanisms of Co(II) mediated reductions of nitriles, alkenes and alkyl halides by LiAlH4 and NaBH4. Those studies have unambiguously identified borides and aluminides of cobalt as catalysts in all three reductions, a finding clearly at odds with commonly held notions about the mechanisms of such processes and which could also be relevant to other transition-metal—hydride systems [12]. [Pg.72]

As mentioned in the preceding text, pack aluminizing is commonly carried out on nickel- and cobalt-base superalloys. Diffusion-coated superalloys develop an aluminide (NiAl or CoAl) outer layer with enhanced corrosion resistance. It is estimated that more than 90% of all coated gas turbine engine hot section blades and vanes made from superalloys are coated by pack cementation and related processes. Detailed information on protective diffusion coatings for superalloys can be found in Ref 24. [Pg.118]


See other pages where Cobalt aluminides is mentioned: [Pg.233]    [Pg.183]    [Pg.183]    [Pg.233]    [Pg.183]    [Pg.183]    [Pg.130]    [Pg.136]    [Pg.108]    [Pg.233]    [Pg.761]    [Pg.410]    [Pg.108]    [Pg.515]    [Pg.460]    [Pg.439]    [Pg.307]    [Pg.117]    [Pg.142]   


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Aluminides

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