sintered NdFeB magnets;multilayer ceramic

作者:A.Ali;A.Ahmad;K.M.Deen;
关键词:sintered NdFeB magnets;multilayer ceramic

coating;permeable defects;rare earths
单位:Department of Metallurgical & Materials Engineering

University of Engineering & Block neodymium magnet
http://www.chinamagnets.biz/Neodymium/Block-neodymium-magnet.php Technology;Department of Metallurgy

and Materials Engineering CEET,University of the Punjab;
摘要:Sintered NdFeB magnets have complex microstructure that

makes them susceptible to corrosion in active environments.The

current paper evaluated the anticorrosion characteristics of

multilayer titanium nitride ceramic coating applied through

cathodic arc physical vapour deposition(CAPVD) for protection of

sintered NdFeB permanent magnets.The performance of ceramic

coating was compared to the electrodeposited nickel coating

having a copper interlayer.Electrochemical impedance

spectroscopy(EIS) and cyclic polarization in simulated marine

environment were employed to determine the rates of coatings

degradation and passivation behaviour respectively.The coating

morphologies and surface chemistry were studied with scanning

electron microscope(SEM).X-ray diffraction(XRD) was used for

identification of component phases in the coatings and the

substrate.The results showed that the polarization resistance of

ceramic coating increased with the exposure time.The rate of

degradation of Rp for the ceramic coating had an extraordinary

negative slope followed by a stable duration,before declining

towards the coating failure.In comparison the nickel coating with

copper interlayer degraded sharply.The vapour deposited ceramic

coating was found to have permeable defects that tended to "re-

passivate" during exposure providing prolonged corrosion

protection to the NdFeB substrate.The magnetic properties were

unaffected and remained at par with the nickel coating having

copper interlayer.