Boriding of steels in a fluidized bed reactor

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. In the present work we used fluidized bed technology (FBT) to deposit boride coatings onto ferrous materials. Impact tests were carried out to determine the fatigue resistance of the examined coatings under dynamic impact loading. During the impact test the alternate impact load strains superficially the layered compound and induces a complex stress state within the coating layer as well as in the interfacial zone of the coating - substrate compound. Both of these stress states are responsible for distinct failure modes such the cohesive and the adhesive one.