Structure and electrical insulation characteristics of plasma-sprayed alumina coatings under pressure

In this work, alumina coatings were fabricated on 316LN austenitic stainless steel by a plasma spray technique. The pressure dependence of the surface electrical resistivity of alumina coatings was investigated in detail. A combination of scanning electron microscopy and X-ray diffraction was employed to understand the microstructure and properties of the as-sprayed alumina coatings. The coatings can endure high pressures under a practical working environment. The surface electrical resistivity of the alumina coatings decreases continuously with an increase in pressure to 250 MPa. Interestingly, the surface resistivity is still greater than 107 Ω·mm for 250 MPa, demonstrating that the coatings have good electrical insulation properties and can be fully utilized in the magnet support of ITER.