Effect of surface modification on mechanical properties and thermal stability of Sm–Co high temperature magnetic materials

Oxidation protection of Sm2Co17-based alloys

“…Using the same approximations, the silica coating (Coating A) at 450 • C (Fig. 5a) gives almost exactly the same level of protection as the electrolytic Ni coating at 500 • C as measured by Chen et al [8].…”

“…The remaining coatings (D, E and G) make little difference to the penetration of the oxidation zone and offer no significant protection. Comparison of these results with those of Chen et al [8] is difficult because their coatings were assessed in terms of magnetic flux losses instead of oxidation zone penetration and at the intermediate temperature of 500 • C. However, magnetic flux losses can be assumed to be equivalent to the volume of the specimen occupied by the IOZ, which can be approximated as A x where A is the surface area of the specimen and x is the IOZ thickness. From Fig.…”

“…5a, uncoated specimens at 450 • C suffer oxidation to a depth of ∼90 m after 600 h which, when multiplied by the specimen's surface area (10 mm × 10 mm × 2 mm ≡ 2.8 × 10 8 m 2 ), gives a volume loss of ∼12.5%. According to [8], the magnetic flux losses at 500 • C after 600 h are just under 12% which means that the volume approximation is good (it will slightly overestimate the volume due to the specimen corners). Using the same approximations, the silica coating (Coating A) at 450 • C (Fig.…”

“…The only work on protective coatings for SmCo magnets (that the authors are aware of) is a study by Chen et al [8], who used electroplated Ni, electroless Ni and electrolytic Ag coatings between 8 and 23 m thick at a temperature of 500 • C, with some success. In this current work the effectiveness of several speculative ceramicbased and metallic coatings, selected from those currently available for use by industrial turbine manufacturers for use in the engine hot sections, is investigated.…”

Bulk anisotropic nanocrystalline SmCo6.6Ti0.4 permanent magnets

“…The crystallographically oriented bulk SmCo 6.6 Ti 0.4 magnets are composed of nanograins with average grain size of $38 nm. An enhanced remanence ratio of up to 0.80 originating from the crystallographic anisotropy was achieved in the nanocrystalline bulks.Permanent magnetic materials operated at high temperature up to 500°C have drawn much attention recently because of their potential applications in a new generation of generators and motors [1][2][3][4]. Earlier research was focused mainly on Sm 2 (Co,Fe,Cu,Zr) 17 alloys, and good magnetic properties at 500°C have been achieved [5-10].…”