Performance of Cr oxide coatings on 304 steel against metal dusting

Evolution of PVD Al oxide coatings in carburizing atmospheres at high temperature

“…The Al oxide had an amorphous structure due to the low deposition temperature, as previously determined by XRD analysis in films obtained in the same conditions [1]. Melo et al [7]. Namely, an initial bump in the first 5 h of exposure, which has been shown to correspond to the formation of a porous unprotective structure, composed of predominantly Fe oxides [7].…”

“…More recently, other studies [10][11][12] emphasized the role of oxygen in the attack of Fe alloys by metal dusting. The effect of oxygen was also observed during exposure of the uncoated 304 L steel to the present atmosphere in which only a minute amount of residual oxygen had great influence on the attack of this material [7]. So, not only impermeability to carbon, but also to oxygen should be considered in the prospective oxide coatings.…”

“…Melo et al [7]. Namely, an initial bump in the first 5 h of exposure, which has been shown to correspond to the formation of a porous unprotective structure, composed of predominantly Fe oxides [7]. Following this bump, a large weight gain is observed up to the end of the experiment.…”

“…The preparation of the samples for the cross section analysis included first the deposition of an electroless Cu layer on the surface to protect the surface as described by Melo et al [7]. To reveal the microstructure, the samples were etched in a solution of 1 part (30 ml) of nitric acid (HNO3), 1 part (30 ml) of hydrochloric acid (HCl) and 1 part (30 ml) of water for~12 s at room temperature (294 K).…”

“…The approach can be extended to other oxide films with similar properties. The use of PVD (Physical Vapor Deposition) oxide thin films in applications of protection against corrosion by metal dusting has been investigated for some time in our research group with encouraging results [7,8]. The selection of oxide thin films as protective coatings was initially based on an analysis of the metal dusting corrosion mechanisms offered by several authors.…”