Chemical heat treatment The chemical heat treatment of forgings is one of the types of heat treatment for forgings. Chemical heat treatment of forgings is the use of chemical reaction, sometimes combined with physical methods to change the chemical composition and structure of the surface of the steel to obtain better technical and economic benefits than homogeneous materials. Process. The performance of the surface layer is particularly important because most failures and failures of mechanical parts germinate in the surface layer, especially in parts that may cause wear, fatigue, metal corrosion, oxidation, and the like. The chemically heat-treated steel parts can essentially be considered as a special composite material. The heart is the original composition of the steel, the surface is the material that infiltrated the alloying elements. There is a tight crystal-type bond between the heart and the surface, which is much stronger than the combination of the heart and the surface obtained by electroplating and other surface resurfacing technologies.
The basic process of chemical heat treatment
1. Decomposition of chemical permeation agents into active atoms or ions;
The osmotic agent forms a reactive medium containing infiltrated elements through a chemical reaction or evaporation at a certain temperature, and then reaches the surface of the workpiece by diffusion of the active atoms in the osmotic agent.
2. Absorption process of active atoms or ions absorbed and dissolved by the surface of steel parts;
The active atom that has penetrated the element is adsorbed on the surface of the workpiece and undergoes phase interface reaction, that is, the adsorption-desorption process occurs between the active material and the metal surface.
3. The diffusion process of the infiltrated element atoms continuously diffuses into the interior.
The adsorbed active atoms diffuse from the surface of the workpiece to the interior and form a solid solution or compound with the metal matrix.
Chemical heat treatment characteristics
1. Metallurgical bonding between the penetrating layer and the base metal, high bonding strength, the penetrating layer is not easy to fall off or peel off.
2. Due to the infiltration of external atoms, a compressive stress layer is usually formed on the surface of the workpiece, which is beneficial to improving the fatigue strength of the workpiece.
3. By selecting and controlling the infiltrated elements and the depth of the infiltration layer, the surface of the workpiece can be given different performance to meet various working conditions.
4, chemical heat treatment is usually not limited by the geometry of the workpiece, and most of the chemical heat treatment has a small deformation of the workpiece, high precision, good dimensional stability.
5, all chemical heat treatment can improve the overall performance of the workpiece surface. Most of them improve the mechanical properties, but also improve the surface layer of corrosion resistance, oxidation, friction reduction, wear resistance, heat resistance and other properties.
6, chemical heat treatment of the workpiece actually has (surface - core) composite material characteristics, can greatly save precious metal materials, reduce costs, significant economic benefits.