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Studies were made on
low temperature ion nitriding of aluminum and its
alloys by dc glow discharge in nitrogen atmosphere.
Aluminum-nitride layers were formed on the surfaces
of aluminum and its alloys even at temperatures
as low as 450 as a result of argon sputtering prior
to nitriding. In this ion nitriding process, not
only formation of nitride layers but also sputtering
of the formed nitride layers due to nitrogen ion
bombardment proceeded simultaneously. The growth
rate of the layers strongly depends on nitriding
temperature and alloy elements. The sputtering rate
depends on nitrogen pressure and glow discharge
voltage. Magnesium and silicon in alloys increase
the growth rate and titanium, vanadium, manganese,
iron and nickel in alloys bring about strong adhesion
between the layer and the substrate. Micro-vickers
hardness of the layers ranged from HV1000 to HV1600,
depending on the kind of alloys. The formed layers
showed excellent resistance to wear compared with
those of commercially available surface treating
such as anodic oxidation, plasma sprays and electrodeposition.
The nitriding provides improved corrosion resistance
in 1N-HCl. The nitriding treatment can be operated
with the apparatus which is similar to a conventional
type for ion nitriding of steels.
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