Kanthal coatings were fabricated by selective laser melting (SLM) with two kinds of powder, 45 similar to 60 mu m and 50 similar to 70 mu m in diameter. The surface morphology, microstructure, element distribution, phase structure, and microwave attenuation properties of the coatings were studied by optical microscope, scanning electron microscopy, X-ray diffraction, and cavity characteristic measurement system. The results indicate that Kanthal coatings have the characteristics of rough surface, porous and flaky structure. The quality factor Q of cavity loaded with coatings fabricated by 45 similar to 60 mu m sphere powder is lower than that of coatings by 50 similar to 70 mu m powder, showing better microwave attenuation properties under the frequency of 2985 MHz. Al2O3 thin films and micro void generated in the structure of coatings have the effect of scattering microwave and thus reduce microwave reflection. It is also shown that flattened shape of Kanthal coatings is a good way to suppress eddy currents in high-frequency electromagnetic field and leads to the formation of easy magnetization planes, which is helpful to enhance the microwave attenuation property. The coating thickness has profound effects on interference loss of microwave. Cavity Q with coating thickness of 0.55 mm reaches the minimum value of 2280. Kanthal coating is composite material whose main mechanism is attributed to magnetic loss.
