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Advantages of Case Hardening

November 22nd, 2017

Not every metal is created equal. Some metals are sturdy and strong, while others are much more malleable and less durable. Steel parts often require treatment to obtain maximum strength and durability. We can change the mechanical properties of metals through the manufacturing process. One method is case hardening. In this process, the metal surface is reinforced through the addition of a thin layer of another metal alloy that increases durability and hardness. Sometimes, this process is called surface hardening. It has many applications, such as producing cooking utensils, reinforcing metal girders and enhancing the functionality of firearms. There are many advantages of the metal case hardening process.

There are many types of case hardening processes. Which one is used will be determined by the metals used in manufacturing and the desired properties of the finished product.

metal case hardening


In carburizing, the surface hardness of the steel is increased by adding carbon to the component. The component that requires hardening is heated to 9000C and exposed to a carbon environment. The carbon penetrates the surface of the metal and strengthens it. The agent used can be solid, liquid or gas. The initial investment costs are generally higher than other processes. In liquid carburizing, it is difficult to control the depth of hardness and it may not be uniform throughout the object. This process must be carried out in a controlled environment to prevent oxygen from being present in the process which changes the outcome of the metal hardening. Partial vacuum processes shorten the time involved and provide a few economic advantages of case hardening.


With this process, the material is heated to about 5500C and then exposed to atomic nitrogen, which can penetrate the steel or iron. Atomic nitrogen reacts with the metal to increase its hardness and resistance. This process offers a high degree of hardness, but cannot be used with all of the alloy steels. Following this process, there may additional manufacturing costs in the form of an expensive grinding process to remove the thin white layer which forms on the surface. However, there are no other heat processes which follow nitriding, which means less deformation to the object.


Cyaniding is a process that introduces both nitrogen and carbon into the case. Typically, it’s liquid carburizing bath that contains cyanide. There are environmental concerns with this method, but there are liquid carburizing baths that use a special grade of carbon instead of cyanide. Thin depths are possible with this process, but it often entails two separate processes to achieve the desired results.

Flame hardening

In this process, the surface of the material is heated with an oxyacetylene flame to a certain temperature, then quenched with water. With this method, the depth of hardening can be easily controlled and there is less distortion of the material, but there is a medium investment cost. However, the product can be used without any additional processes. In this method, selective parts of the item can be hardened without treating the entire object. Also, flame hardening required skilled operators to ensure that the product is treated correctly.

Induction hardening

Induction heating is a quicker process that can be included in the manufacturing process. An inductor coil heats the surface layers of the material, allowing the depth of the hardening to be easily maintained. Following the procedure, light machining may be required, but the process has a low energy consumption with a high output rate. However, irregular shapes do not work well with this process. Set up costs might be high.

Benefits of Case Hardening

Objects which need to have a hard exterior to endure wear and tear while maintaining a soft interior to withstand shock benefit from case hardening. The advantages of case hardening are:

  • Creating a more durable product
  • Increases wear-resistance of the metal
  • Increases lifetime of objects
  • Case hardening makes steel easier to weld
  • The metal is more flexible
  • Steel is tougher and stronger

Case hardening can be a beneficial process in many industries, but the right process must be used to get the right outcome. Case hardening is not compatible with welding. It’s important to work with experienced engineers who understand case hardening to get the desired effect on your final product. When you need solutions that concern case hardening, make sure it’s done right the first time and applied properly to save money down the road.

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