The carburization process

This treatment, also known as cementation, is used to increase the hardness of the material and its resistance to abrasion, while maintaining its softness and the core’s ductility. This effect can be achieved by carburizing the surface layers of steel. Please note that this type of heat treatment is only used in steel with a carbon content of up to 0,25%. Steel is heated to 850-900oC during the process of carburization. The carburizing process takes between 3 and 20 hours, depending on the thickness of the surface layer in which the changes resulting from the carburization are to occur. The workpieces are then hardened and tampered.

Piro-carb Vacuum Carburising

Thanks to its high-tech furnaces, Sacher also offers modern Piro-carb vacuum carburization technology. It does not oxidize or deform the material and leaves a clean surface for details. It is also faster than a conventional process and as such – is more environmentally friendly due to lower energy consumption.

How does steel carburizing work?

As we have already mentioned, this effect is achieved by coating steel surface layers with carbon. However, how does this process work in detail?

As steel has a crystalline structure, it is necessary to heat the material (up to the previously mentioned levels of 850-900°C) to allow it to become carburized, i.e. saturated with carbon. In addition, it is also necessary to ensure case-specific concentrations of carbon atoms in the immediate vicinity of the surface to be improved. The diffusion phenomenon is then used to move to the correct phase of the introduction of carbon atoms into the structure of steel. This phenomenon allows the material previously accumulated in its vicinity to absorb carbon. Absorption occurs until the concentration level between the sites even out and later turns into depth diffusion.

Throughout the entire process of carburization, the supply of free carbon atoms into steel’s structure can occur both by means of an appropriate liquid solution and by using solid bodies or gases. After the steel has been activated (by heating), the carbon atoms move through the structure of the crystal network until the nearest free nodes are reached.

How much time diffusion or, more generally, carburization will take depends largely on the availability of free atoms of the described element in the vicinity of the material, as well as on the temperature of the material.

Steel carburization is carried out within heterogeneous media. An example of the presence of a solid body is, for example, a powder derived from charcoal enriched with activator additives. In terms of liquids, salts such as carbonate and alkali metal chloride are mainly used. What about carburization using gasses?

It is most often based on using carbon monoxide or methane and is very popular, as it provides superior control over the amount of carbon present in the environment. It is also worth noting here that plasma based ion-carburization is also possible, as well as vacuum carburization described by us earlier in this subsection. The latter is also referred to as low pressure, high temperature carburization.

Full list of advantages resulting from Vacuum Carburization

The high-temperature carburization offered by Sacher is characterized by numerous advantages over alternative techniques. We briefly touched upon it earlier, focusing solely on the speed of the process and on the lack of oxidation and distortion in the material being improved. As such, below is a complete list of the key benefits that this carburization variant offers:

– the ability to precisely control the dimensions and the enormous repeatability,
– high and even undersurface hardness of the carburized components throughout the entire profile,
– product purity is substantially higher than that achieved using conventional machining techniques,
– a significantly reduced number of operations for the entire production procedure, including, for example, no need for final cleaning or sanding,
– excellent control over the uniformity of hardness, microstructure and depth of diffusion layers,
– the option of carburizing even very small and non-pass-through holes
– the absence of an internal oxidation zone, in other words, the elimination of internal oxidation, which results in optimized mechanical and fatigue properties of the machined components.

Steel carburization with Sacher

At Sacher, we work hard to deliver perfect results for every order, while also maintaining attractive service resources. With our years of experience, solid and constantly updated industry knowledge and a wealth of technical resources, you can be confident that we’ll be able to professionally carry out any carburization process you request and do so on the basis of a design that focuses on maximizing performance. We would like to cordially invite you to contact our staff.