Carbonitriding treatment is a process in which the activated carbon atoms and nitrogen atoms decomposed by the infiltrating agent are used to penetrate into the surface of the workpiece at a temperature of 820-860 °C. For the dual effect of nitriding, the co-infiltration time is related to the thickness of the infiltration layer, the temperature and the medium used, and the carbon and nitrogen content of the co-infiltration layer depends on the co-infiltration temperature.
When the co-infiltration temperature of carbonitriding treatment increases, the carbon content increases and the nitrogen content decreases; when the co-infiltration temperature decreases, the carbon content decreases and the nitrogen content increases. 15% to 0.5%, mostly used for low carbon steel, medium carbon steel and alloy steel, etc. There are three types of infiltration agents: solid, gas and salt bath. After carbonitriding, quenching and low-temperature tempering are carried out. The surface structure after tempering is nitrogen-containing martensite + retained austenite + a small amount of carbon and nitrogen compounds, and the core is low-carbon martensite or medium-carbon tempered horse. body.
After carbonitriding treatment, the surface hardness, wear resistance and fatigue strength are improved on the premise of ensuring high toughness inside the workpiece, and nitrogen reduces the formation temperature of austenite, so the workpiece can be realized at a lower temperature. Co-infiltration; and the workpiece can be directly quenched after co-infiltration, which is not easy to overheat, and the deformation of the workpiece is small; the hardenability of the infiltration layer can be improved, and it can be quenched in a moderate medium; the infiltration rate is fast, and the operation cycle is short.
Compared with it, the surface of the steel parts after carburizing has obtained a carbon content of more than 0.8%. Methanol as a diluent can improve the hardness, wear resistance and fatigue strength of the workpiece surface under the premise that the core of the carburized part has a certain strength and toughness, so as to obtain excellent comprehensive mechanical properties.
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