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What is Oil Cementation under Vacuum?

Oil carburising under vacuum is a process that involves heating metal parts in a furnace filled with oil and carburising compound. The purpose of this process is to improve the surface hardness, wear resistance and corrosion resistance of metal parts.


What is Oil Cementation under Vacuum?
What is Oil Cementation under Vacuum?

The process consists of four main steps: preparation, heating, cooling and cleaning. In the preparation step, the metal parts are cleaned and degreased to remove dirt, oil or rust. The cementing compound is a mixture of carbonaceous materials such as charcoal, graphite or coke and additives such as chromium, manganese or silicon. The cementing compound is placed in a container and covered with oil. The metal parts are then placed in the container and immersed in the oil.


In the heating step, the container is placed in a vacuum oven and heated to a temperature between 800°C and 1000°C for several hours. The vacuum prevents oxidation and reduces gas formation in the oil. The oil acts as a carrier of carbon and other elements from the cementing compound to the surface of the metal parts. Carbon diffuses into the metal and forms a hard layer called the sheath. The other elements form alloying compounds that improve the properties of the sheath.


In the cooling step, the container is removed from the furnace and cooled slowly to room temperature. The cooling rate affects the microstructure and hardness of the container. A slower cooling rate produces a softer and more ductile case, while a faster cooling rate produces a harder and more brittle case.


In the cleaning step, the metal parts are removed from the container and cleaned with solvents or alkaline solutions to remove excess oil or cementing compound. The metal parts are then ready for machining or use.


Oil carburising under vacuum is a widely used technique for surface hardening of steel parts such as gears, shafts, bearings and tools. It offers several advantages over other methods such as carburising or nitriding. Some of these advantages are as follows:


- It produces a uniform case depth and hardness throughout complex shapes and geometries.

- Reduces distortion and cracking of metal parts due to low thermal stresses.

- Improves the lubricity and anti-friction properties of metal parts due to the presence of oil.

- Allows precise control of carbon content and other elements in the case by adjusting the composition and amount of the cementing compound.

- Reduces environmental pollution and energy consumption by using less oil and gas than conventional methods.

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