Chemical heat treatment is a heat treatment process that places steel parts in an active medium at a certain temperature for insulation, allowing one or several elements to penetrate its surface layer, in order to change the chemical composition, structure, and properties of the surface layer of the steel part.
Chemical heat treatment consists of three basic processes: decomposition, absorption, and diffusion. Firstly, under certain conditions, active elemental atoms are decomposed from the medium; Then the active atoms infiltrate into the surface of the steel part, forming a certain thickness of infiltration layer to achieve the purpose of chemical heat treatment
At present, the most commonly used chemical heat treatments in the manufacturing industry are carburizing, nitriding, and carbonitriding.
(1) Carburizing of steel: carburizing is a heat treatment process in which steel parts are heated and insulated in a carburizing medium to allow carbon atoms to infiltrate the surface of the steel parts. The purpose is to increase the surface hardness and wear resistance of steel components. Important parts such as shafts, gears, and fine yarn machine steel rings in textile machinery are mostly subjected to carburizing treatment.
(2) Nitriding of steel: Nitriding is a chemical heat treatment process that allows active nitrogen atoms to infiltrate the surface of steel parts at a certain temperature. The purpose of nitriding is to improve the hardness, wear resistance, thermal hardening, fatigue strength, and corrosion resistance of the surface layer of steel parts.
The temperature of nitriding is low, and quenching is not required after nitriding, therefore, the deformation of steel parts is small; The nitrogen infiltrated surface has high hardness and wear resistance, as well as thermal hardening and corrosion resistance, and the fatigue strength of steel parts is high. But the nitriding layer is thin and brittle, and cannot withstand impact and vibration. Due to the long production cycle and high prices of equipment and nitriding steel, the production cost is high.
Therefore, nitriding is suitable for precision parts that require wear resistance, high temperature resistance, and corrosion resistance on the surface, such as precision gears, precision spindles, cylinder liners, valves, etc.
(3) Carbon nitrogen co infiltration of steel: Carbon nitrogen co infiltration is a chemical heat treatment process in which carbon and nitrogen atoms are simultaneously infiltrated into the surface of steel parts. This process is a combination of carburizing and nitriding, combining the advantages of both. Currently, there are two widely used methods in production: low-temperature gas carbonitriding and medium temperature gas carbonitriding