Single and Multielement Coatings in a Fluidized Bed Reactor

Abstract

Heat treatments of alloys in fluidized bed reactors have been carried out for more than twenty-five years. Recently this technology has been used for surface engineering applications in the deposition of hard and/or corrosion resistant layers e.g. aluminizing, chromizing, nitriding, carburizing, boronizing. The fluidized bed method is simple, efficient, environmentally friendly and capable of immediate adjusting the furnace atmosphere for specific requirements e.g. production of multielement coatings. The boride coatings on steel have an excellent combination of properties e.g. high fatigue strength and wear resistance. On the other hand silicide coatings are well known for their excellent corrosion resistance. Boron-siliconizing in fluidized beds is a promising method to improve both the wear and corrosion properties of steels. In the present paper fluidized bed technology (FBT) was used to deposit boride and boron-silicide coatings on steels. The coatings were examined by means of electron and optical microscopy and X-Rays diffraction, in terms of the coatings composition, morphology, thickness and phase formation. The coatings tribological properties were evaluated under dry wear.