This document discusses diffusion and various diffusion processes. It describes diffusion as the movement of atoms from an area of high concentration to low concentration due to concentration differences. It also discusses factors that influence diffusion like temperature, atom size, and material structure. Specific diffusion processes covered include carburizing, nitriding, and carbonitriding which involve diffusing carbon, nitrogen, or both into steel to increase hardness.

1. HERU IKHSANI YUSBAR
05 171 053
Mechanical engineering andalas university, 2008
DIFFUSION
/HERU
IKHSANI
YUSBAR

2. Mechanical engineering andalas university, 2008
DIFFUSION
KONSENTRASI RENDAH
PERPINDAHAN ATOM
DARI KONSENTRASI TINGGI
KARENA ADANYA PERBEDAAN
KONSENTRASI ATOM
PENYEBAB
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3. Mechanical engineering andalas university, 2008
DIFFUSION
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4. Mechanical engineering andalas university, 2008
DIFUSI PADA CUNi
DIFFUSION
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5. Setelah material mengalami difusi, maka akan terjadi
perubahan sifat material tersebut
Sifat yang di maksud :
•Sifat fisik
warna
•Sifat mekanik
Kekuatan tinggi
Tahan aus
Contoh :
pada roda gigi dilakukan karburizing
krn perlu kekerasan yang tinggi pada permukaannya
agar lebih tahan aus, tahan gesek, dan berumur panjang
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DIFFUSION
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6. Mechanical engineering andalas university, 2008
FAKTOR YANG MEMPENGARUHI
 JENIS DIFUSI
•VACANCY DIFFUSION
•INTERTITIAL DIFFUSION
KENAIKAN ENERGI
KINETIK ATOM
(GETARAN)
TEMPERATUR NAIK,
MEMBANTU
PROSES DIFUSI
DIFFUSION
 TEMPERATUR

7. Kedalaman
(mm)
Waktu (jam)
PENGARUH TEMPERATUR
TERHADAP KEDALAMAN ATOM
BERDIFUSI
DIFFUSION
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8. Mechanical engineering andalas university, 2008
 KOEFISIEN DIFUSI (D0)
MEMPUNYAI NILAI YANG BERBEDA UNTUK SETIAP ATOM
DIFFUS

9.  UKURAN ATOM YANG BERDIFUSI
ATOM YANG MEMILIKI UKURAN YANG LEBIH KECIL
AKAN LEBIH MUDAH BERDIFUSI
 TYPE (SEL SATUAN)
•BCC (BODY CENTERED CUBIC)
•FCC (FACE CENTERED CUBIC)
Mechanical engineering andalas university, 2008
DIFFUSION

10. Mechanical engineering andalas university, 2008
DIFFUSION MECHANISM :
•INTERTITIAL DIFFUSION
•VACANCY DIFFUSION
DIFFUS

11. Mechanical engineering andalas university, 2008
VACANCY DIFFUSION
DIFFUSION
an substitutional atom exchanges its
position with the neighboring vacancy

12. Distance
Atom
Vacancy
E
Energy
UNTUK PINDAH, PERLU ENERGI
DIDAPAT DARI PANAS (THERMAL ENERGY)
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13. INTERTITIAL DIFFUSION
FASTER THAN VACANCY DIFFUSION,
SOME ATOMS WHICH DIFFUCE
INTERTITIAL IS C, H, DAN O
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DIFFUSION
impurities which have small ionic radii can
travel directly from one interstitial site to
another one
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14. Mechanical engineering andalas university, 2008
MATEMATICS OF DIFFUSION :
• STEADY STATE DIFFUSION
• NON-STEADY STATE DIFFUSION
DIFFUSION

15. Mechanical engineering andalas university, 2008
STEADY STATE DIFFUSION
TIDAK ADA PERUBAHAN KONSENTRASI
ATOM YANG LARUT
JUMLAH ATOM YANG BERPINDAH LINIER
JUMLAH ATOM YANG BERPINDAH DALAM JARAK TERTENTU
DI TIAP TITIK SAMA
DIFFUSION

16. Mechanical engineering andalas university, 2008
J= FLUX / ALIRAN ATOM (Kg/M2)
D= KOEFISIEN DIFUSI
•TIAP ATOM MEMPUNYAI KOEFISIEN DIFUSI YANG BERBEDA
HUKUM I FICK :
•Tanda (–) berarti atom berpindah dari konsentrasi tinggi ke
konsentrasi rendah
DIFFUSION

17. Mechanical engineering andalas university, 2008
NON-STEADY STATE DIFFUSION
JUMLAH ATOM YANG BERPINDAH DALAM JARAK TERTENTU
DI TIAP TITIK TIDAK SAMA
DIFFUSION

18. Mechanical engineering andalas university, 2008
DIFFUSION’S CLASSIFICATION BASED ON
THE MOVING ATOM
•KARBURIZING
•NITRIDING
•KARBUNITRIDING
DIFFUSION

19. Carburizing is the best method
for low carbon steels.
The carburizing process does not harden
the steel. It only increases the carbon
content to some predetermined depth below
the surface to a sufficient level to allow
subsequent quench hardening
•CARBURIZING

20. CARBURIZATION PROCESSES
•PACK CARBURIZATION
•GASS CARBURIZATION
•LIQUID CARBURIZATION
All of the carburizing processes (pack, gas, liquid)
require quenching from the carburizing temperature
or a lower temperature or reheating and quenching.
Parts are then tempered to the desired hardness.

21. CARBORIZING PRODUCTS :
RODA GIGI
PUNCHING TOOLS
SPROCKETS
BEARING

22. •PACK CARBURIZATION
Carburizing Time: 4 to 10 hours
Carburizing Temperature:
1750 O F
It is difficult to quench the part immediately, as the
sealed pack has to be opened and the part must be
removed from the pack. One technique that is used
often is to slow cool the entire pack and subsequently
harden and temper the part after it is removed from the
sealed pack.

23. •GAS CARBURIZATION
The advantage of this process over pack carburizing is an
improved ability to quench from the carburizing temperature.
Most carburizing gases are flammable and
controls are needed to keep carburizing gas
at 1700 oF from contacting air(oxygen)
COMMON GASS THAT USED :
•methane,
•ethane,
•propane,
•natural gas

24. •LIQUID CARBURIZATION
GENERALLY USED SODIUM CYANIDE (NaCN)
Cycle times for liquid cyaniding is much shorter
(1 to 4 hours) than gas and pack carburizing
processes.
DISADVANTAGES :
•ENVIRONMENTAL PROBLEM
•EXPENSIVE

25. NITRIDING
In this process, nitrogen is diffused into the surface of the
steel being treated.The reaction of nitrogen with the steel
caused the formation of very hard iron and alloy nitrogen
compounds (harder than carburized steel)
ADVANTAGE :
•HARDNESS IS ACHIEVED WITHOUT THE OIL OR WATER QUENCH
•CAN BE USED FOR CERTAIN TYPE OF STEELS SUCH AS CHROMIUM-
MOLYBDENUM ALLOY STEEL OR NITRALLOY-TYPE STEELS

26. Nitriding temperature is below the lower critical temperature of
the steel and it is set between 925 oF and 1050oF.
The nitrogen source is usually Ammonia (NH3). At the nitriding
temperature the ammonia dissociates into Nitrogen and
Hydrogen.

27. • Punches
• Forging Dies
• Extrusion Dies
• Extrusion Screws
• Springs
• Piston Rings
• Casting Dies
• Plastic & Rubber Molds
• Gears
• Couplings
Nitriding for a Variety of
Manufactured Parts
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28. CARBONITRIDING
This process involves with the diffusion of both
carbon and nitrogen into the steel surface.
Carbonitriding is performed at temperatures
above the transformation temperature of the
steels (1400 oF -to 1600 oF)

29. The process is performed in a gas atmosphere
furnace using a carburizing gas such as
•Propane or Methane (source of carbon)
•Ammonia (source of nitrogen)
The advantages of this process is :
•It can be applied to plain carbon steels
•Produc’s surface wear characteristics is
better than carburizing

30. Terima kasih
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