Chemical and thermal treatment of metals and alloys

Chemical heat treatment technology is used to increase the strength and durability of finished products. Thanks to this technology, the surface of the part becomes resistant to corrosion, cavitation and strength. The service life is also extended. The product becomes more reliable. When the outer layer of the metal is subjected to this type of treatment, solid substitution substances are formed on its surface. Nitrogen and carbon are responsible for the formation of a solid solution of embedding. The formation of a protective layer is quite fast. The energy consumption depends on the characteristics of the metal – gamma iron takes longer than alpha iron.

The main types of technology

We offer to consider different types of chemical heat treatment.

Cementation

This type of treatment for alloy steel and alloy and low carbon steel is carried out using carbon and its compounds in different states. The substance used to introduce the carbon is called a carburizer. This technology in the process of using the carbon saturation technique is effective at very high temperatures (up to 950 degrees). After carburizing, the metal is also hardened and tempered.

Thanks to the use of this type of technology and processing at high temperature, the workpiece becomes resistant to twisting, as the outer layer becomes very strong, but the inner component of the metal retains its flexibility. This processing method can be used even at home if you have the appropriate equipment. The gas carburizing method can only be used in industrial environments.

Nitriding

This process involves holding the metal in an ammonia atmosphere at a temperature of 650 degrees. During the holding process, nitrogen chemically reacts with the alloy components. This results in the formation of metal nitrides, which have exceptional strength. Nitriding technology allows the metal to resist rust, increase wear resistance and improve strength.

This process is widely used in the automotive industry. The high strength of steel treated with this technology is maintained even at temperatures of 500 degrees. Nitriding takes place at lower temperatures and the treated metal surface does not change shape.

Nitro cementation and cyanidation

These technologies are used to introduce sufficient carbon and nitrogen into the metal surface. This reduces fatigue, increases wear resistance and provides corrosion protection. Nitro cementation is carried out under the influence of ammonia and methane gases. Depending on the function of the future metal product, the billet is subjected to low- or high-temperature treatment. Low-temperature processing is used for various high-speed steel tools. The high-temperature method is suitable for products made of low-alloy and carbon steel. The technology is in demand due to its low price and safe processing. After the processing is complete, the workpiece is quenched and tempered. Hardening is performed inside a special furnace. After nitro-cementation, a fine-grained layer is formed with carbonitrides evenly distributed within it. The thickness of this layer is usually no more than 1000 microns. It is also possible to form a thicker layer, but this will lead to the formation of defects, which in turn causes a deterioration in the metal’s characteristics. Gas-assisted nitro-cementation is used for products with non-standard geometric shapes.

Liquid cyanidation is also commonly used, which is carried out by exposing the metal to cyanide salts at a temperature of 900 degrees. In this case, carbonates and chlorides are exposed to the metal. Cyanidation has the following advantages:

• Low time and low energy consumption.
• Rare cases of marriage, because they do not deform.
• This technology can replace cementation and nitriding under certain conditions. Cyanidation has one drawback: the high cost of the process.

This type of treatment also requires special training due to the high level of danger associated with the high toxicity of cyanide.

Boronization

This process creates a very strong surface layer saturated with boron. The process is performed at a temperature of 900 degrees. Iron borides appear in the interior of the layer, which increases resistance to abrasion and corrosion. Boriding is often used on molds and other equipment.

Siliconization

The finished protective coating has a porous structure and low strength. However, if the siliconized surface is treated with oil at a temperature of 200 degrees, the hardness of the metal can be increased. This process makes the part resistant to acid and marine corrosion.

Companies and individuals can order metal heat treatment services such as cementation, hardening, annealing, normalizing, and nitriding. To order a service, please call the phone numbers listed on the website.