Samarium Cobalt Magnets have SmCo5 and Sm2Co17, whose theoratical max working temperature is from 250-350℃, compared with NdFeB Magnet, SmCo Magnet is more suitable to work under higher temperature. 

SmCo5  is easier than Sm2Co17 to make small size magnet, mini disc and ring shape and other irregular shapes. Under high working temperature,  Sm2Co17 maintains magnetic properties better than SmCo5. So it is widely used  for high temperature motor, magnetic pump and so on. 

Although both NDFEB and SMCO magnets are made from Rare earth materials, Samarium  Cobalt Magnets have better corrosion resistance ability in comparison with Neodymium magnets, so it does not need any coatings. But certainly we can make Nickel coating if any requirements on it.