Page 6 - Vol_1_Chapter_VI

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Fig. 6. 1 Surface engineering

6.2 Carburization

Carburization is a process which involves adding a hard, protective shell to the outside of an otherwise
soft steel. This process allows for intricately shaped metals to possess a strength and toughness that
they otherwise wouldn't be able to possess. One of the most sophisticated and common forms of case
hardening is carburizing. This is a method which involves introducing steel items to carbon atoms. 2
There is not just one carburization process available. In fact, generally, there are four different types
of carburization used. Each different process offers its own advantages and disadvantages.
− Vacuum Carburization
− Liquid Carburization
− Pack Carburization
− Gas Carburization

Vacuum Carburization

Process description
The vacuum carburizing process involves taking iron, steel or alloy steel and infusing it with carbon in
order to make it harder. First, the metal is placed in a vacuum furnace and heated to the correct
temperature. Then propane gas is released into the furnace. As a result of the heat, the propane breaks
down into the elements carbon, hydrocarbon and hydrogen. The carbon diffuses into the metal,
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making it harder (Fig. 6. 2).

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