HIGH TEMPERATURE GAS NITRIDING TREATMENT OF AISI 430 USING LOW AND HIGH PURITY NITROGEN GAS
ABSTRACT: The properties of
stainless steels can be improved by high temperature gas nitriding (HTGN) treatment.
The improving of their properties are obtained from nitrogen atom which diffuse
intostainless steel. Nitrogen gas is the main source of nitrogen atom on the
HTGN treatment. Generally, these treatment use high purity of nitrogen gas. The
aim of this research is to investigate the effect of nitrogen gas purity on the
HTGN treatment for AISI 430. Stainless steel AISI 430 plate 2 mm thick was
processed by HTGN treatment. The specimens was exposed at nitrogen gas
atmosphere at temperature 1200oC and held for 2 hours prior quenching in water.
The treatment used industrial/welding grade (99.5%) as low nitrogen gas purity
and ultra high purity (UHP) grade (99.999%) as high nitrogen gas purity. The
vickers micro-hardness test was conducted to evaluate the hardness distribution
from surface into middle section of the specimens before and after treatment. Light
optical microscope was applied to examine the microstructure of specimens after
treatment. Metallographic examination shows both treatments using low and high
purity gas have the same grain size. However HTGN treatment using low purity of
nitrogen gas produces hardness slightly lower than the high purity. This is due
the high content of impurity of the low purity gas that reduces the partial pressure
of nitrogen gas. Another effect of impurity is the reaction between nitrogen
gas and its impurity especially oxygen gas. These reactions reduce the amount
of free nitrogen atom which diffuses on the stainless steel.
Penulis: Agus Suprihanto
Journal Code: jptmesingg160006
