1. Government Engineering College
Gandhinagar
MECHANICAL TESTING & CARBURIZING OF
TRANSMISSION GEAR IN AUTOMOBILE
Presented By:
• Patel Mihir H. (120130121009)
• Nadoda Hitesh D. (110130121025)
Guided by :
• Pro. Harsad Jadav
• Pro. Parth Bharmbhatt

2. OBJECTIVES
The main purpose of this project is experimental study of pack
carburizing of low alloy steels.
This study was conducted by using a Muffle furnace at campus.
This process is carried out at 8800C temperature for 2.30 hour.
Quenching medium is used here is air quenching.
From the experiment, the surface hardness and thickness of
carbon layer was different than original sample.
2

3. SAE 8620
SAE 8620 Steel Rod SAE 8620 Steel Gears

4. SAE 8620
SAE 8620 is a hardenable chromium, molybdenum, nickel low alloy steel, often used for
carburizing to develop a case-hardened part.
This case-hardening will result in good wear characteristics.
In gear industry mostly all gear are made from many different material.
SAE 8620 grade of steel is mostly used in automobile application
Power-transmission gears involve a wide variety of steels and cast irons.
In all gears, the choice of material must be made only after careful consideration of the
performance demanded by the application end-use and total manufactured cost.

5. WHY SAE 8620 ? Chemical
Steel in its basic form is a mixture of iron and carbon.
Increasing the carbon content increases the strength and hardness but reduces the ductility.
Producing a gear that is strong hard, and resistant to brittle failure is important, so special
alloying metals are added to the steel.
The addition of the elements allows the carbon levels to be kept moderate, preventing brittle
failure.
The three most prevalent costly metals used to alloy with gear steel are nickel, molybdenum,
and chromium.
These three metals alloyed together into the steel produce a material that is strong and tough
due to the nickel, hard and corrosion resistant because of the chromium, and thoroughly
hardened by the molybdenum.

6. Chemical Composition Of SAE 8620

7. Mechanical Properties
Properties Metric
Hardness, Rockwell B 80
Hardness, Vickers 155
Machinability 65

8. Muffle Furnace (at campus)
We use the muffle furnace at 8800C temperature for 2.30 hour for each sample.
It is very easy to use just set the temperature
It will reach the temperature very fast and now wait for soaking time as long you need.
Now open and take out sample for quenching process.

9. Sample of SAE8620
The sample we use here are SAE 8620 steel rod.
With the diameter of 16mm
And 4 inch long
Chemical Analysis of SAE8620
Mechanical hardness of this sample is 82
Component C Mn S P Si Ni Cr Mo Al
percentage 0.19 0.74 0.026 0.028 0.24 0.42 0.45 0.16 0.033

10. Experimental process
For study the pack carburizing process we need the sample which is SAE 8620 steel rod we used.
And for carburizing process we bring some pack carburizer from online market which carburizer are
BaCO3.
We grinded this all coal and pack carburizer in same size which is 600 microns .
Carburising process is done in two different circumstances,

11. Cont.
Condition of Process 1 :-
Pack all the coal in one box with one sample of SAE 8620 which is surrounded by coal.
Condition Of Process 2 :-
In other box, the sample is surrounded by pack carburizer(BaCO3) &Coal

12. Cont.
Now For Carburising process ,
This box are heated in muffle furnace for 2 hour and 30 minute at 8800C .
For some different result and study different process we don’t quenched them just make them
to slow cooling with the furnace

13. Machines are use in Process
Muffle Furnace Rockwell Hardness TesterJaw Crusher

14. Coal & Pack carburizer and the sample

15. Microstructure of SAE 8620
As Received condition Carburized sample with coal Carburized sample with carburizer

16. Mechanical Testing of SAE 8620
Mechanical testing will shown the result of the carburising process which is how much effective
on the sample during the process
And how deep carbon diffuse and how much hardness is change
Mainly hardness is main properties of the material which can show entire area of the
application of the material

17. Change In Properties
Mechanical properties of the SAE 8620 is change.
It’s hardness is increase due to carburizing process
Because as carbon percentage is increase in SAE 8620 its became more hard and tough.
Sample As Received Carburized with
coal
Carburized with
carburizer
Hardness 82 89 92

18. Conclusion
By this experimental study of pack carburizing process with SAE 8620,
By our study on carburising is suggest that if you need hardness only on thin layer of surface
there is chance with short time and low temperature
than ideal process you can get it. And if you need hardening in deeper core then you must
follow ideal condition for as today used.
We can also do some extra experiment like changing the pack carburizer, increase the time and
change the temperature.

19. THANK YOU