Gas Nitriding versus Ferritic Nitrocarburizing in Surface Hardening of Extrusion Dies
George J. Tymowski and Achilles Nikopoulos, Nitrex Metal Inc., Montreal, Canada
Track: EXTRUSION/DIE, PRACTICAL - Tooling Performance
ABSTRACT --- Both nitriding technologies are used extensively to enhance
wear resistance of extrusion dies. The referenced technologies differ in the type
of the nitriding case configuration they produce. Controlled gas nitriding carried
out at the low nitriding temperature range produces typically a very hard, wear
resistant nitrided case with relatively low toughness levels. The controlled ferritic
nitrocarburizing process (FNC) carried out at the higher end of the nitriding
temperatures spectrum produces less hard and less wear resistant nitrided case.
While high hardness/wear resistance at the die bearing may be the desirable
effect of die nitriding, the inadequate die handling procedures, often leading to
die flaking, frequently overshadow the benefits of good wear resistance. The
different structure and stress distribution of the nitrocarburized case plays
therefore an important role in overcoming one of the common die failure modes
such as flaking and corner chipping in or around the bearing area of the die.
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