Gaseous cementation: a guide

What is gas cementation?

Gas cementation is a thermochemical process used in the metallurgical industry to improve the surface properties of metallic materials. This thermochemical treatment involves the introduction of chemical elements, typically carbon and nitrogen, into the metal surface by diffusion into an atmosphere rich in these elements at elevated temperatures. In particular, gas cementation or gaseous carbocementation is used to increase the hardness, wear resistance and corrosion resistance of metal parts.

Advantages and disadvantages compared with other types of cementation

Gas carburizing offers several advantages over other thermochemical treatment methods. Among the main advantages is the ability to achieve high treatment depths compared to other processes, allowing significant improvements in the wear and fatigue resistance of components. In addition, the ability to precisely control the chemical composition of the gas atmosphere allows for uniform and repeatable results. However, gas carburizing can have some disadvantages, such as the need for high energy consumption and longer cycle times than other thermochemical treatment processes.

The process of gaseous cementation

The gaseous carburizing process is based on the principles of atomic diffusion and chemical reaction between the gaseous atmosphere and the metal being treated. At high temperatures, carbon or nitrogen atoms in the atmosphere react with the surface of the metal, penetrating its crystalline structure. This atomic diffusion occurs through the intersection points between crystalline grains, changing the surface properties of the material.

Treatment Phases

Gas carbocementation is divided into several basic steps, each of which plays a crucial role in achieving the desired properties of the treated material.

  • Pre-treatment: In this stage, the surfaces of the metal components are prepared by cleaning, degreasing, and descaling operations in order to remove any surface impurities that could compromise the metal carburizing process.
  • Heating: The metal components are then heated to high temperatures inside a controlled atmosphere furnace or chamber. The treatment temperature depends on the type of material and process specifications, but is generally between 850°C and 1050°C.
  • Exposure to carbon or nitrogen atmosphere: During this step, heated components are exposed to an atmosphere rich in carbon or nitrogen. Carbon or nitrogen atoms in the atmosphere penetrate the surface of the metal, diffusing through its crystal structure.
  • Cooling: Once the exposure phase is completed, the components are gradually cooled to allow the formation of a cemented surface structure. Cooling can be done in a controlled manner inside the oven or by immersion in cooling liquids.

Process parameters (temperature, time, atmosphere)

Key process parameters for gas cementation include temperature, treatment time and atmosphere composition.

  • Temperature: Temperature is one of the most critical factors and directly affects the rate of diffusion of carbon or nitrogen atoms into the metal surface. Higher temperatures can accelerate the gaseous carburizing process, but it is essential to avoid overheating to prevent deformation or damage to components.
  • Time: The exposure time to the carbon or nitrogen atmosphere depends on the desired depth of carburizing and the chemical composition of the base material. A longer treatment time allows greater penetration of the elements into the metal surface, but a balance must be struck to avoid undesirable phenomena such as over-cementation.
  • Atmosphere: The composition of the atmosphere used during treatment is essential to ensure the formation of a uniform and homogeneous surface layer. The most common atmospheres are those rich in carbon (e.g., methane gas or carbon gas) or nitrogen (e.g., ammonia in the case of carbonitriding), but mixed atmospheres can also be used to achieve specific effects.
cementazione gassosa trattamento

Applications of gaseous carbocementation

Gas carburizing represents a versatile process with numerous applications in various industries that require improved wear, corrosion and fatigue resistance of metal parts. In the automotive and aerospace industries, for example, it is used extensively to improve the surface properties of critical components such as crankshafts, gears, bearings and valves that must be able to withstand intense mechanical stresses and extreme conditions such as high temperatures, high pressures and corrosive environments.

In the oil and gas industry, where components are subjected to high loads and corrosive environments, gas carburizing is used to improve the strength and durability of pump shafts, valves, piping, and drilling equipment, thus helping to reduce maintenance costs and improve plant reliability. Also in the steel and metallurgical industries, this treatment is essential for treating components such as rolling shafts, gears and metalworking tools to ensure resistance to high stresses during production and machining processes.

Simply put, gaseous carbocementation is essential to ensure reliable and durable performance of components in multiple industrial applications and contribute significantly to the quality and reliability of manufactured products.

ATP Europe: Expert in stop-off protective coatings for metals

ATP Europe offers solutions for protection during gas carburizing: stop-off suprficial coatings. These coatings are formulated to protect specific areas of metal parts that should not undergo heat treatment during the gas carburizing process.

ATP Europe’s stop-off metal surface coatings for gas carburizing are composed of special formulations that can withstand the high temperatures and chemical action of the carburizing atmosphere.They are applied to metal surfaces prior to heat treatment and create a protective barrier that prevents the diffusion of carbon or nitrogen atoms into the designated areas. The precise application of stop-off coatings is critical to ensure that only the desired areas of the metal part undergo the gas carburizing treatment, thus avoiding undesirable alterations in mechanical or surface properties. Specifically with regard to gaseous carburizing, the most effective product is METSEAL-300, a water-based stop-off coating for use primarily on steel.

Choosing ATP Europe as a supplier of stop-off coatings for gas carburizing offers customers the assurance of high-quality, customized solutions supported by a team of experts. The combination of experience, quality, technical support and innovation makes ATP Europe the ideal partner to meet protection needs during the heat treatment of metals.

Contact ATP Europe for more information for stop-off coatings for gas cementation or to request a quote! We are always available to show you the best product for your needs.