Thermal spraying

Quantum mechanics

Metallurgy

Materials science

Coating

Salt spray test

Neodymium magnet

Physics

Alloy

Microstructure

Composite material

Corrosion

Magnet

Journal of Magnetism and Magnetic Materials

AlCoCrFeNi high-entropy alloy (HEA) coating was formed on the surface of sintered NdFeB magnets by high-velocity oxygen-fuel (HVOF) spraying. The surface and fractured cross-sectional morphologies, phase composition and corrosion resistances of the coating were investigated using SEM, XRD, accelerated corrosion immersion test and electrochemical test, respectively. At the same time, the effect of AlCoCrFeNi coating on magnetic properties of NdFeB magnet was also studied. The results show that the surface of HEA coating exhibits the typical spraying morphologies, and the thickness is approximately 15 μm. The HEA coating is mainly composed of single BCC phase, and has little effect on the magnetic properties of the NdFeB magnet. In the sulfuric acid immersion test, few bubbles can be generated on the surface of the HEA coated sample after immersed for 300 min, and the weight loss is only 0.49 g/dm2, only 0.93 % of the uncoated sample. In the electrochemical test, the AlCoCrFeNi coated NdFeB sample also shows better corrosion resistance than the uncoated NdFeB sample. The present work provides a promising coating to improve the corrosion resistance of sintered NdFeB magnets.

Microstructure and corrosion resistance of AlCoCrFeNi high-entropy alloy coating on sintered NdFeB magnets prepared by HVOF spraying