Metals and alloys undergo various heat treatment processes to obtain changes in terms of their general properties and microstructures. Most of the time, these processes can strengthen the structure of the mentioned materials by heating and cooling activities. They can likewise relieve stresses, increase surface hardness, amplify strength, and make them easier to machine or weld.
A wide array of heat treatment processes can now be utilised in altering the properties of metals and alloys. Some of these processes include annealing, case hardening, precipitation strengthening, quenching, and tempering. Another process that can be done to specific types of metals is carbonitriding.
An Overview of Carbonitriding
Before knowing what carbonitriding is, you should understand two concepts first. One of these concepts is the case hardening process. The case hardening process is a process of granting metals additional thin layer of harder metal on their surfaces while retaining their softness underneath. Another concept that you should know about is carburising. Carburising is a thermochemical process wherein low carbon steels are diffused with carbon, yielding a durable surface layer.
And with these two concepts, carbonitriding can now be easily understood. Carbonitriding is a case hardening process that closely resembles the carburising technique. Just like carburising, carbonitriding also integrates carbon into metals for them to have durable surfaces. Nitrogen, however, is also added during the carbonitriding process, further increasing the wear resistance and surface hardness of metals being processed. A hardened surface layer is expected out of this process.
Carbonitriding Main Processes
When conducting the carbonitriding process, metal workpieces are often heated in a sealed chamber before adding the nitrogen and carbon elements. The temperature of the heating process typically ranges between 820 to 900°C. During the heating, the workpieces are expected to generate some phase changes on their crystal structure, allowing carbon and nitrogen elements to diffuse into them easily.
The amount of carbon that is added to the workpieces typically ranges between 0.5 to 0.8%, while the amount of nitrogen added to the same workpieces would range between 0.2 to 0.4%. Most metal workpieces that undergo carbonitriding are plain carbon steel or low alloy steel since they do not harden well with other heat treatment processes.
To ensure metal workpieces will obtain high surface hardness and ductile core, the entire carbonitriding process should take from a few hours up to a day. Once the diffusion process is completed, the workpieces are then directly quenched in oil.
Key Benefits and Applications
As previously stated, the carbonitriding process helps metals attain a strong, durable, and wear-resistant case. Distortion and quench cracking among metal workpieces are likewise reduced as carbonitriding only requires lower temperature and slower quenching speed compared to other processes. Aside from obtaining this type of case, this process can also benefit industries since it can cater to a cleaner mass production of small metal components.
All these benefits of carbonitriding make them great for producing small components such as gears, shafts, rollers, bearings, pistons, and levers in various systems.
To know more about carbonitriding, you can call us at Alpha Detroit Heat Treatment.
The general properties of metal materials allow them to undergo numerous processes. These processes can help modify and even improve their core properties so that they can be useful for a lot of industries.
One of the processes that can be done on metals is carburization. Carburization is a process that hardens the exterior of metals by diffusing carbon atoms into their surface and other workable layers. Metals that undergo carburization often have low tensile strength and hardness, preventing them from withstanding wear and tear after prolonged use. Through carburization, their strength and hardness are expected to improve given the integration of carbon to the metals.
An Overview of Carburization
Carburization, as previously stated, entails the hardening of metal workpieces through diffusing carbon atoms into their surface and other possible layers of the materials. Before the process is conducted, the surface and other parts that will be diffused with atoms will be cleaned first to remove any contaminants. During the process, the metal workpiece is heated in an environment filled with carbon-rich solids, liquids, or gases. Over time, these carbon sources will decompose, allowing the carbon atoms to be liberated and subsequently diffused into the metal workpiece.
The duration of the process typically depends on the temperature of the heating. It is also affected by the carbon potential of the workpiece. Ferrous metals can fully maximise the effects of carburization, particularly those that are comprised of low carbon.
Aside from obtaining better strength and hardness, carburization allows metal workpieces to attain better corrosion resistance, improved fatigue strength and mechanical strength, remarkable toughness, respectable wear resistance, and relieved internal stresses.
Positive and Negative Impacts
The process of carburization, as expected, can bring tons of positive impacts to the processed metal workpieces. As stated earlier, the process allows metal materials to develop hardened layers, improving their mechanical strength, fatigue strength, toughness, wear resistance, durability, corrosion resistance, ductility, and surface hardness. With the improvements over these qualities, metal workpieces that undergo carburization are projected to last for a long time.
The depth of the hardened layers or cases may be altered based on the applications of the metal materials. Metal workpieces that must be replaced all the time may have a shallow hardened case, while those that must sustain shock loads or crushing loads may benefit from higher case depths.
But just like other processes, carburization may also have some negative impacts or limitations. For metal workpieces that are asymmetrical, the application of carburization to these materials may lead to stress build-up and cracking due to the cooling rate differential. These things may also happen if the process is done with nonuniform materials. Aside from these effects, carburization can also yield expensive machining costs due to the consistent changes in dimensions, shapes, and distortions during the process.
To know more about carburization, feel free to give us a call at Alpha Detroit Heat Treatment.