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SURFACE TREATMENTS
Bright Finish
A bright finish tool has no surface treatment and is suitable for general
purpose use.
Blue Finish
A blue finish is achieved by steam tempering - a thermal process
which imparts a non-metallic surface to the tool. This surface is
porous and by absorbing lubricant, helps prevent rusting, reduces
friction and cold welding, resulting in increased tool life.
Steam tempered products can successfully be used at slightly
increased machining rates or on more difficult to machine materials.
Gold Oxide
This is a metallic brown coloured surface treatment achieved by a
low temperature temper and is normally only used on cobalt products
for identification purposes.
Nitriding
Nitriding imparts a hard surface to the tool and is used for prolonging
tool life and machining difficult to machine materials. Because
nitriding makes the edge more brittle, care must be exercised in the
type of application.
Nitrided tools are normally also steam tempered.
Titanium Nitride Coating (TiN)
TiN coating is a very hard, gold coloured surface coating a few
microns thick which is applied bymeans of a complex process, called
Physical Vapour Deposition (PVD), by advancedmodern equipment.
The coating is non-metallic and therefore reduces cold welding.
In certain applications increased speed and feed rates can be
achieved because of:
(a) The hardness of the coating.
(b) The reduction in cutting force required due to a decrease in
friction between the tool and the workpiece.
Tool performance will deteriorate after re-sharpening.
