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Carbonitridingis a metallurgicalsurface modificationtechnique
that is used to increase the
surfacehardnessof a metal, thereby reducingwear.
During the process, atoms of carbonandnitrogendiffuse
interstitially into the metal, creatingbarriers to slip, increasing
the hardness andmodulusnear the surface. Carbonitriding is
often
applied to inexpensive, easily machined low carbon steel to
impart the surface properties of more
expensive and difficult to work grades of steel.[1!urface
hardness of carbonitrided parts ranges
from "" to #$ %&C.
Certain pre'industrialcase hardeningprocesses include not only
carbon'rich materials such as
charcoal, but nitrogen'rich materials such as urea, which
implies that traditional surface
hardening techniques were a form of carbonitriding.
Contents
[hide
1(rocess
$Characteristics of carbonitrided parts
)*dvantages
+*pplications
"!ee also
#&eferences
Process[edit
Carbonitriding is similar to gascarburiationwith the addition of
ammoniato the carburiing
atmosphere, which provides a source of nitrogen. -itrogen is
absorbed at the surface
anddiffusesinto the workpiece along with carbon. Carbonitriding
around /"0 C 2 1""0 34 iscarried out at temperatures substantially
higher than plain nitriding around ")0 C 2 550 34 but
slightly lower than those used for carburiing around 5"0 C 2
1600 34 and for shorter times.
Carbonitriding tends to be more economical than carburiing, and
also reduces distortion
during quenching. 7he lower temperature allows oil quenching, or
even gas quenching with a
protective atmosphere.
Characteristics of carbonitrided parts[edit
Carbonitriding forms a hard, wear'resistant case, is typically
0.06 mm to 0." mm thick, andgenerally has higher hardness than a
carburied case. Case depth is tailored to the application8
https://en.wikipedia.org/wiki/Surface_modificationhttps://en.wikipedia.org/wiki/Surface_modificationhttps://en.wikipedia.org/wiki/Hardnesshttps://en.wikipedia.org/wiki/Hardnesshttps://en.wikipedia.org/wiki/Wearhttps://en.wikipedia.org/wiki/Wearhttps://en.wikipedia.org/wiki/Wearhttps://en.wikipedia.org/wiki/Carbonhttps://en.wikipedia.org/wiki/Carbonhttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Slip_(materials_science)https://en.wikipedia.org/wiki/Young's_modulushttps://en.wikipedia.org/wiki/Carbonitriding#cite_note-1https://en.wikipedia.org/wiki/Carbonitriding#cite_note-1https://en.wikipedia.org/wiki/Case_hardeninghttps://en.wikipedia.org/wiki/Case_hardeninghttps://en.wikipedia.org/wiki/Case_hardeninghttps://en.wikipedia.org/wiki/Ureahttps://en.wikipedia.org/wiki/Carbonitridinghttps://en.wikipedia.org/wiki/Carbonitriding#Processhttps://en.wikipedia.org/wiki/Carbonitriding#Characteristics_of_carbonitrided_partshttps://en.wikipedia.org/wiki/Carbonitriding#Advantageshttps://en.wikipedia.org/wiki/Carbonitriding#Applicationshttps://en.wikipedia.org/wiki/Carbonitriding#See_alsohttps://en.wikipedia.org/wiki/Carbonitriding#Referenceshttps://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=1https://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=1https://en.wikipedia.org/wiki/Gashttps://en.wikipedia.org/wiki/Carburizinghttps://en.wikipedia.org/wiki/Carburizinghttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Diffusionhttps://en.wikipedia.org/wiki/Diffusionhttps://en.wikipedia.org/wiki/Quenchinghttps://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=2https://en.wikipedia.org/wiki/Hardnesshttps://en.wikipedia.org/wiki/Wearhttps://en.wikipedia.org/wiki/Carbonhttps://en.wikipedia.org/wiki/Nitrogenhttps://en.wikipedia.org/wiki/Slip_(materials_science)https://en.wikipedia.org/wiki/Young's_modulushttps://en.wikipedia.org/wiki/Carbonitriding#cite_note-1https://en.wikipedia.org/wiki/Case_hardeninghttps://en.wikipedia.org/wiki/Ureahttps://en.wikipedia.org/wiki/Carbonitridinghttps://en.wikipedia.org/wiki/Carbonitriding#Processhttps://en.wikipedia.org/wiki/Carbonitriding#Characteristics_of_carbonitrided_partshttps://en.wikipedia.org/wiki/Carbonitriding#Advantageshttps://en.wikipedia.org/wiki/Carbonitriding#Applicationshttps://en.wikipedia.org/wiki/Carbonitriding#See_alsohttps://en.wikipedia.org/wiki/Carbonitriding#Referenceshttps://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=1https://en.wikipedia.org/wiki/Gashttps://en.wikipedia.org/wiki/Carburizinghttps://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Diffusionhttps://en.wikipedia.org/wiki/Quenchinghttps://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=2https://en.wikipedia.org/wiki/Surface_modification
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a thicker case increases the wear life of the part.
Carbonitriding alters only the top layers of the
workpiece8 and does not deposit an additional layer, so the
process does not significantly alter
the dimensions of the part.
9aximum case depth is typically restricted to 0.6" mm8 case
depths greater than this take toolong to diffuse to be economical.
!horter processing times are preferred to restrict the
concentration of nitrogen in the case, as nitrogen addition is
more difficult to control than carbon.
*n excess of nitrogen in the work piece can cause high levels
ofretained austeniteand porosity,
which are undesirable in producing a part of high hardness.
Advantages[edit
Carbonitriding also has other advantages over carburiing. 7o
begin, it has a greater resistance
to softening during temperingand increased fatigueand impact
strength. :t is possible to use
both carbonitriding and carburiing together to form optimum
conditions of deeper case depths
and therefore performance of the part in industry. 7his method
is applied particularly to steels
with low case hardenability, such as the seat of the valve. 7he
process applied is initially
carburiing to the required case depth up to $." mm4 at around
500'5""C, and then
carbonitriding to achieve required carbonitrided case depth. 7he
parts are then oil quenched, and
the resulting part has a harder case than possibly achieved for
carburiation, and the addition of
the carbonitrided layer increases the residual compressive
stressesin the case such that the
contact fatigue resistance and strength gradient are both
increased.
https://en.wikipedia.org/w/index.php?title=Retained_austenite&action=edit&redlink=1https://en.wikipedia.org/w/index.php?title=Retained_austenite&action=edit&redlink=1https://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=3https://en.wikipedia.org/wiki/Tempering_(metallurgy)https://en.wikipedia.org/wiki/Fatigue_(material)https://en.wikipedia.org/wiki/Fatigue_(material)https://en.wikipedia.org/wiki/Residual_stresshttps://en.wikipedia.org/w/index.php?title=Retained_austenite&action=edit&redlink=1https://en.wikipedia.org/w/index.php?title=Carbonitriding&action=edit§ion=3https://en.wikipedia.org/wiki/Tempering_(metallurgy)https://en.wikipedia.org/wiki/Fatigue_(material)https://en.wikipedia.org/wiki/Residual_stress
