ta 201 l10
Post on 24-May-2015
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Pearlite Martensite Bainite
Transformation of Austenite
γ-Fe
PearliteAustenite
MartensiteAustenite
Furnace
Water Bucket
R. Martens
Martensite
Martensite
Hardness of Martensite
BainiteAustenite
Feathery appearance
Fe3CFerrite
T-T-T Diagram
T-T-T Diagram
Pearlite
Bainite
Martensite
www.worldpress.com
Mechanical Property
Case Hardening:Gears
www.gearandstuff.com
Spur GearsBevel Gears
Worm Gears
Helical Gears
Sproket
Fatigue Failure of Gears Tooth failed!
Scars on worm wheel surface!
Internal surface cracked!
Case Hardening of Gears
Carburizing
Nitriding
Carbo‐nitriding
Carburizing
Carburizing is a process of adding Carbon to the surface. This is done by exposing the part to a Carbon rich atmosphere at an elevated temperature and allows diffusion to transfer the Carbon atoms into steel.
Carburizing Process
Heat the gears to 850 ‐9500 C
Burn some carbonaceous gas(CH4 , C2H6 C3H8 in O2 )
2CO ↔ CO2 + C
CH4 + 3/2O2 ↔ CO +2H2O
↔ Diffuse ↔ Fe3C
•Gas carburizing
•Plasma carburizing
•Salt bath carburizing
•Pack carburizing
Carburizing
Carburizing: Case Depth
NitridingNitriding is a surface-hardening heat treatment that introduces nitrogen into the surface of steel at a temperature range (500 to 550°C), while it is in the ferrite condition. Thus, nitriding is similar to carburizing in that surface composition is altered, but different in that nitrogen is added into ferrite instead of austenite
Plasma Nitriding
Carbo‐nitriding ProcessCarbonitriding is a modified form of gas carburizing, rather than a form of nitriding. The modification consists of introducing ammonia into the gas carburizing atmosphere to add nitrogen to the carburized case as it is being produced.
Induction Hardening
Precipitation HardeningWidely used in aluminum‐copper alloys
Courtesy: Boeing
Precipitation Hardening Process
κ
κ+θ
κ+L
Precipitation Hardening Process
Precipitation Hardening Microstructure
κ
κ κκ
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