What is Oxidation? How to Apply?

Oxidation, or darkening, is a practice that increases the corrosion resistance of the metal used. A degreasing process is applied to the metal before the process, which operates at high temperatures. In this way, a dark black appearance is formed on the coated metal and the process is continued with protective oil. In metal injection applications where oxidation adhesion and related adhesive wear occur, the process of forming an oxide film with lubricating properties on the mold surface occurs. After the process, the 2-5 µm thick Fe2O3 and Fe3O4 iron oxide film formed on the surface creates a barrier between the mold and the molten metal and prevents adhesion due to mechanical and intermetallic phase formation. It is very important to apply the oxidation process before first use, especially in molds with complex figures where cooling may be insufficient or lubricant and coolant spray are difficult to reach. Oxidation Properties Conductivity, black oxidation reduces conductivity by at most 1%. This makes it a suitable process for electrical parts as well. It is not brittle and, unlike painted or coated parts, there is no hydrogen embrittlement in black oxidation. However, caustic brittleness may occur in very hard parts and very thin springs. However, this situation can be minimized by controlling the oxidation process times. What is the Purpose of the Oxidation Process? Oxidation is a process applied especially to hot work tool steels to prevent adhesion and increase wear resistance. It cannot be applied to all kinds of molds. In this regard, the knowledge and experience of the heat treater becomes important, and the oxidation process can also be used specifically to increase the cutting life of high-speed steels after the special nitriding process. What are the areas where oxidation is used? Some of the areas where gas nitriding and oxidation are used can be listed as follows. These can be listed as aluminum injection molds, gas shock absorber shafts, pump shafts, textile machinery parts, gun parts and automotive mechanical parts. https://www.aht.com.tr/