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quench-temper (QT) samples reflect formation of fine
martensite with precipitation of carbides.
The precipitation of carbides (M
23
C
6
) with different
sizes was observed. The size and shape of carbides are
a function of both heat input and initial microstructure.
Lower and moderate heat input (Figs. 3a and b) result
in fine carbide particles compared to higher heat input
(Fig. 3c), which has very large carbide particles.
Figure 4 shows the influence of heat treatment on
the hardness of AISI 420. Heat treatment increases
hardness, which can be caused by the formation of a
finer microstructure. On the other hand, the volume
fraction and size of the carbide particles present in the
stainless steel and the amount of retained austenite
Fig. 3—
QT heat treatment influence on AISI 420 microstructure: (a) Low heat input (P=200 W, V=1000 mm/s);
(b) Moderate heat input (P=300 W, V=1000 mm/s); and (c) High heat input (P=300 W, V=800 mm/s).
(a)
(b)
(c)
25
m
m
Fig. 4 —
Heat input and heat treatment influence the hardness
of 420 stainless steel.
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A D V A N C E D
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