Oxidation-resistant nanocrystalline coatings

The corrosion behavior of sputtered Ni-based superaUoy K38 nanocrystalline coatings in molten sulfate (75 wt.% Na2S04 + 25 wt.% K2SO4) was investigated at 900 °C in air. The results indicated that nanocrystaUization triggers rapid formation of a protective oxide layer. The addition of yttrium to the coating improved its corrosion resistance [38]. 

X. Peng, F. Wang, Oxidation - resistant nanocrystalline coatings. Development in high-... 

New prospects for the development of coating materials resistant to high-temperature sulfide corrosion have been created by combined alloying of common metals with molybdenum and aluminum and in particular by the development of novel nanocrystalline aluminum based refractory metal alloys containing silicon which are highly resistant to both sulfidizing and oxidizing environments. 

To increase the wear resistance of surfaces, silicon and metals are often coated with a hard nitride, carbide, boride, or oxide film. Nanoindentation and fracture simulations have been used extensively to elucidate failure mechanisms of these typically more brittle surfaces, which include crack propagation and film delamination. Considerable attention has also focused on nanocomposite materials, which possess nanocrystalline inclusions in an otherwise amorphous matrix. The nanocrystalline component is sufficiently small to preclude the formation of stable dislocations, and thus provide a higher hardness. 

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