Manufacturer’s Guide to Heat Treatment of Large Gears

15 January 2021

Industries such as mining, construction, marine, and energy usually utilise the capabilities of large gears. And as these industries foresee a growing demand for tools and equipment that rely primarily on these mentioned gears, the production of these gears is now more prioritised compared before.

Just like any other tools and equipment, large gears must be able to resist wear and other elements that could negatively affect their functions and longevity. One way to ensure their durability and reliability is through effective heat treatment methods. Though, different manufacturers maximise varying heat treatment processes in producing high-quality large gears. 

Heat Treatment Processes for Large Gears

Some of the most notable heat treatment processes for large gears include carburising, nitriding, induction hardening, and through hardening. These processes have unique approaches in making sure that the specifications of the large gears can meet the needs and demands of industries.

  • Carburising: Manufacturers usually carry out carburising to increase the pitting, wear, and impact resistance of the large gears. With carburising, large gears are expected to boast greater mechanical properties and strength. One of the downsides of this process, alternatively, is that it can cause distortion. Carburising large gears likewise require additional processes that can increase costs. 
  • Nitriding: Nitriding, alternatively, is carried out to form a thin layer at the surface part of the large gears. Compared to a carburised surface, the surface made by nitriding is much harder, making the large gears more resistant to wear and corrosion. This heat treatment process can also avoid distortion. Nitriding, however, may not meet certain metallurgical results and specifications. 
  • Induction Hardening: Induction hardening is done by heating the areas that need to obtain high strength and wear resistance through localised induction fields. With this process, a hard layer on the gear tooth surface and the root is produced, which can be great for added wear resistance.
  • Through Hardening: Through hardening may have been around for a long time. However, it is known for minimising the decarburising of the large gears in the austenitic range. This process is conducted by heating the gears under a protective atmosphere, quenching them in oil or other similar media, and ultimately tempering them. 

Challenges in Heat Treating Large Gears

Heat treatment processes may be effective in enhancing the properties of large gears. But there are few factors that can affect these processes as well as their respective outcomes. For one, the final part dimensions of large gears can be hugely affected by these processes, especially if residual stresses are not eliminated properly. And as the size of the gears increases, the challenges of distortion are known to be greater. In fact, problems with distortion may also occur during the final heat treatment step.

Other challenges that manufacturers often encounter during the heat-treating process of large gears are temperature uniformity, carbon uniformity within the process gas, transport of gears from one furnace component to the other, investment and running costs, the construction of the quenching equipment, and meeting the expertise needed for an effective heat-treating application.

For more information about heat treating large gears, just contact us at Alpha Detroit Heat Treatment. 

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