PLASMA SPRAYING OF HIGH-NITROGEN-BEARING STEELS FOR WEAR-RESISTANT COATINGS AND STRUCTURAL APPLICATIONS

Thermally sprayed coatings of high-nitrogen-bearing steel for corrosio n resistance and wear applications were investigated. High-nitrogen st eels represent a new class of engineering materials, Additions of nitr ogen enhance the strength, corrosion resistance, and hardness of auste nitic stainless steels without sacrificing low-temperature ductility a nd fracture toughness, In addition, the precipitation of nitrides at t he grain boundaries is slower compared to that of ferrous carbides, th us increasing the elevated-temperature use of the steels, The objectiv e was to take advantage of these properties and produce high-nitrogen steels via plasma spraying. An Fe-18Cr-18Mn steel with 0.61 wt% N was air and vacuum plasma sprayed over steel and aluminum substrates. Plas ma spraying was conducted with Ar/H-2, Ar/He, and Ar/N-2 plasma gases in air, vacuum, and nitrogen atmospheres,It was found that the nitroge n atmosphere increased the nitrogen and nitride content of the coating s and improves wear and corrosion properties. The sprayed coatings wer e characterized for nitrogen and oxygen content, porosity, hardness, a nd wear resistance.