With its high magnetic energy product and excellent performance, Sm-Fe-N magnets have been increasingly widely used in motors, 传感器, magnetic separation and other fields. 然而, when many users choose or use SmFeN magnets for a long time, they often ask such questions: What level of stability can this material achieve? And how to improve its reliability in high temperature, humidity or other harsh environments?
To answer this question, we first need to figure out what the so-called “stability” mainly includes. Is it that the magnetic properties decrease more slowly over time, or that the magnets demagnetize less under high temperature conditions? Or is it to prevent the material itself from decomposing and pulverizing?
Why are SmFeN magnets easy to demagnetize?
Many people may be curious, since the performance of SmFeN magnets is so good, why is stability an issue that needs to be focused on? 实际上, the nitride of SmFeN is relatively less stable than that of SmCo magnets. Nitrogen elements are easy to escape at high temperatures, causing the lattice structure to be destroyed. 此外, this material is also sensitive to moisture. If the surface is not effectively protected, the oxidation reaction will gradually corrode the interior, resulting in the deterioration of magnetic properties. 所以, improving stability is inseparable from the dual improvement of material organization and external protection.
Improving stability from the material itself
First, optimizing the alloy composition is an effective means. 例如, adding an appropriate amount of titanium, aluminum and other elements during the preparation process can help improve the solid solution stability of nitrogen in the lattice and reduce nitrogen loss at high temperatures.
Secondly, it is also important to control the powder particle size and distribution. Too small a particle size will lead to an increase in specific surface area and increased oxidation sensitivity, while too large a particle size is not conducive to uniform sintering. Through strict screening and surface treatment, the corrosion resistance and demagnetization resistance of the material in the later use process can be significantly improved.
此外, the use of atmosphere protection sintering (such as nitrogen or hydrogen protection) can reduce the intrusion of impurities during the sintering process and stabilize the nitride structure.
Outer layer protection: must or optional?
Usually, many manufacturers will coat or electroplate the magnet products before leaving the factory. When the magnet needs to be exposed to a humid or high temperature environment for a long time, the importance of the coating is self-evident.
Common surface treatments include epoxy coating, nickel or zinc electroplating, chemical plating, ETC。, which can not only block oxygen and moisture, but also improve surface wear resistance.
For applications that require extremely high reliability, double-layer coating (such as electroplating first and then spraying) can further improve the protection effect.
此外, in addition to materials and protection, can the use conditions themselves be improved?
If the operating temperature of the magnet is close to its maximum operating temperature (usually around 150°C), even with the best protection, it is difficult to avoid performance degradation. Reasonably lowering the operating temperature and avoiding long-term humid or high-salt spray environments are simple and effective ways to improve stability.
In later applications and maintenance, regular inspections are equally important. Once the coating of the magnet is damaged or corroded, it should be repaired or replaced as soon as possible to prevent further oxidation penetration. Some manufacturers also provide packaging solutions to place the magnet in a closed cavity to further extend the service life.
总之, the stability of SmFeN magnets cannot be completely solved by a single technology or measure, but requires multiple dimensions from raw materials, processes, surface protection to usage management.
If you are considering purchasing or applying this type of magnet, you might as well ask yourself: How high a stability is required for your usage conditions and performance requirements? What targeted improvements should be made in the production and application links? Only on the basis of a full understanding of your own needs can you find a more suitable solution for you.
