Advantages and Disadvantages of Powder Metallurgy Gears

Whether by weight or by quantity, the proportion of powder metallurgy (PM) and metal injection molding (MIM) gears is much larger than that of PM parts in other fields. Gears, ratchets and cams are all suitable for powder metallurgy, because, in terms of powder metallurgy and MIM gears, besides low cost and high production efficiency, there are also the following advantages.

(1) The dimensional accuracy of powder metallurgy gears produced in large quantities is uniform, especially when carbide die is used.

(2) Because of the porosity in the material structure, it is helpful for the gear to run smoothly and self-lubricate.

(3) Powder metallurgical gears with blind angle can be made, which can eliminate undercutting and retracting grooves when cutting gears. When making this kind of gear by powder metallurgy, special support is needed at the blind end.

(4) Gear can be combined with other shape parts, such as cam, ratchet, other gears, etc., and integrated production can be realized by powder metallurgy process.

(5) Bevel gears, bevel gears with equal diameter, helical gears and other special tooth-shaped gears can be made.

(6) Standard involute gears can be made, which is simpler and cheaper than other methods.

(7) The ratchet wheel, like the gear, is easily manufactured by powder metallurgy and MIM. Root cutting should be avoided, and large radius should be allowed at the top and root of teeth.

Powder metallurgy and metal injection molding have the characteristics of excellent surface roughness, uniform performance among parts and self-lubrication, which is especially advantageous for making gears and cams. Sintered cams with self-lubricating properties often have more durable surfaces than grinders. Powder metallurgy gears can be formed at one time, which not only saves cost, but also improves productivity.

Harbermetal is a professional manufacturer and solution provider of metal powder injection molding process (MIM) and PM process. We provide our customers with high volume structural, functional and appearance parts of various materials with high precision, complex shapes, good performance and exquisite appearance, and we have the ability to develop ceramic and titanium alloy materials to meet the needs of different types of customers. The company mainly provides all kinds of precise and complex hardware structure parts and components to worldwide enterprises in the fields of 3C consumer electronics, new energy, drones, medical devices, automobiles, aerospace, civil consumer goods …… etc.

Powder metallurgy has lots of advantages, such as material saving, energy saving, high efficiency, suitable for mass production, good size and shape repetition, low noise and low wear when gears are running etc., so it has been widely used. The main defects are impacting resistance and poor impact function. Therefore, it is very important to enhance its strength.

A. Strength characteristics of powder metallurgy gears

1. The expansion coefficient of materials and the accuracy of dies mostly depend on the accuracy of powder metallurgical gears. Generally, the domestic die for gear within 50 diameters is between 8-9 grades, while the imported die is between 7-8 grades. If it is helical gear, it can also be a higher grade. The greatest advantage of powder metallurgy gear is that it can be produced in large quantities and has good consistency.

2. For ordinary FN0205 powder metallurgy gear, it can carry torque up to 14NM, warm-pressed parts can reach 20NM, and warm-pressed FD0405 can reach 25NM. Therefore, in the case of professional powder metallurgy design, gears weight can still be reduced by 30-40%.

B. Increasing the strength of powder metallurgical gears

1. For high strength powder metallurgical gears, they should have high density and follow the process of “pressing-preheating-reheating-heat treatment”.

2. Lower carbon content can ensure that the product has high surface hardness and wear resistance in heat treatment. Low carbon will make the product have excellent impact resistance.

3. Adding 2%-3% Ni and 2% Cu into the material can obviously improve material impact strength after sintering.

4. Compared with carburizing and quenching, carbonitriding products have excellent wear resistance. Lower carbonitriding temperature guarantees parts core strength and reduces the quenching deformation.