42CrMo Gear Vacuum Nitriding Treatment

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A gear is a mechanical element that continuously meshes with gears on the rim to transmit motion and power. The main mechanical properties of the safe operation of gears are bending fatigue strength, contact fatigue strength, scratch resistance and gluing resistance, wear resistance, etc. The wear resistance of the gear after nitriding is 70% to 80% higher than that of the carburized gear, and the high scratch resistance and high anti-seizure ability are the specialties of the nitriding layer. Therefore, in addition to high-speed and heavy-duty gears, the use of nitriding treatment is increasingly recognized by more and more people. Vacuum nitriding can improve the strength and toughness of the nitriding layer, reduce deformation and improve accuracy. Therefore, in recent years, the gears for light vehicles have intentionally adopted vacuum nitriding technology in order to further improve the quality, reduce the deformation and reduce the cost.

Nitriding treatment refers to a chemical heat treatment process in which nitrogen atoms penetrate into the surface of the workpiece in a certain medium at a certain temperature. Nitrided products have excellent wear resistance, fatigue resistance, corrosion resistance and high temperature resistance, and increase the wear resistance, surface hardness, fatigue limit and corrosion resistance of steel parts.

Process flow:

(1) Gear material and parameters

Gear material is 42CrMo (nitriding). Parameters and accuracy of the test gear: modulus m=5mm, helix angle β=0º, tooth width b=20mm, pressure angle α=20º, stress correction coefficient Yst=2.0, root fillet parameter qs=2.5, root circle The corner surface roughness Rz≤10μm, and the precision is ISO1328-1:1995 grade 5.

(2) Gear processing procedures and related indicators

The technological process of nitriding gear is:

Blanking → forging → normalizing → roughing → quenching and tempering → semi-finishing → hobbing → finishing → grinding → nitriding → assembly. Quenching and tempering hardness requires 290 to 330HBW. Nitriding adopts gas nitriding, and the nitriding temperature is 520-530℃.

After testing, the higher surface hardness, core hardness, better hardness and microstructure uniformity of gears after nitriding are beneficial to the improvement of fatigue life of nitrided gears, and higher residual compressive stress is also beneficial to the improvement of fatigue life.

Equipment selection: The RVN series vacuum nitriding furnace produced by SIMUWU is a high-quality product for the vacuum heat treatment process of tooling and molds. Good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum nitriding process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.