Types of Nitriding Processes and Their Primary Advantages

10 January 2023

Various types of metals frequently undergo heat treatment so they can be formed into various parts and products. Heat treatment is an important process for industries since it can help alter the physical properties of metal workpieces. This process can introduce changes to metals as it exposes them to almost extreme temperatures.

Industries carry out different heat treatment techniques so they can attain their needed metal parts and products. Some of these techniques include annealing, tempering, carburising, quenching, normalising, case hardening, and precipitation strengthening.

Another heat treatment technique that industries can take advantage of is nitriding. Nitriding is a heat treatment technique that introduces nitrogen into the metal surface, creating a case-hardened finish to the workpiece. Metals that can undergo this heat treatment technique include low-alloy steels, aluminium, molybdenum, and titanium.

Primary Purposes of Nitriding

The formation of the case-hardened finish is possible as the nitrogen atoms latch onto the surface of the component. This finish can likewise form once nitrogen atoms are diffused along the grain boundaries and within the grains of the metal workpieces. The nitriding process is often done at temperatures of 350 to 590 degrees Celsius. As the temperature decreases, the time needed for the nitriding to reach a certain depth of the workpiece increases.

One of the primary purposes of nitriding is to achieve a high hardness on the surface of a workpiece. This heat treatment technique can also increase the wear resistance of the workpiece, improve its fatigue life, and enhance its corrosion resistance. Nitriding can likewise provide a high-temperature property to the surface of the workpiece.

Types of Nitriding Processes

There are three types of nitriding processes that are often maximised by different industries. These processes are gas nitriding, plasma nitriding, and salt-bath nitriding.

1. Gas Nitriding: The gas nitriding process involves the heating of metal to an optimal temperature while being in contact with ammonia or other nitrogenous gases. Once the gas reaches the surface of the heated workpiece, it tends to break down into hydrogen and nitrogen, which leads to the formation of the nitride layer. Gas nitriding only requires low equipment costs compared to other nitriding options. It can also work with workpieces in huge batches. Precautions, however, must be done when working with nitrogenous gases.

2. Plasma Nitriding: Plasma nitriding utilises a plasma discharge of reaction gases so that the workpiece surface can be heated. This process is done by using intense high-voltage electric fields to create ionised nitrogen gas molecules or plasma. The plasma will then accelerate to clean the surface, heat the workpiece, and generate active nitrogen ions. This nitriding process does not cause too much distortion. It is also energy-efficient and quick. It does not even require the workpiece to undergo further machining or polishing.

3. Salt-Bath Nitriding: Salt-bath nitriding is a process that uses molten salt to draw nitrogen. It also maximises carbon that is released by the decomposition of cyanide into cyanate. Usually, a workpiece is immersed in a bath of preheated molten cyanide salt. A hard and ductile iron nitride outer layer is then introduced into the workpiece as time passes. Salt-bath nitriding can be advantageous for industries since it is quick and straightforward.

To expose your workpieces to nitriding, you can contact us at Alpha Detroit Heat Treatment.

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