Scientists decode how exotic alloys corrode, pointing to tougher industrial coatings
Researchers used advanced X-ray analysis to map exactly how a five-metal alloy oxidizes and breaks down in acidic conditions. The findings reveal a precise sequence for how nitrogen bonds with different metals in the material—intelligence that could guide the design of more durable coatings for aerospace, chemical processing, and other harsh-environment industries.
Originaltitel: Near-surface analysis of magnetron sputtered AlCrNbYZrN<sub>x</sub> high entropy materials resolved by HAXPES
<p>Hard X-ray photoelectron spectroscopy (HAXPES) was used to perform a non-destructive depth profile of AlCrNbYZrN<sub>x</sub> (x = 0 to ∼50 at.%) thin films. The outermost native oxide of the pristine thin films contained the highest coordination oxides of every metal. Substoichiometric oxides or oxynitrides were found underneath. After exposure to 1.0 M HCl, increases in the most highly coordinated oxides of Cr, Nb, and Al in films with up to 37 at.% N were observed, suggesting that the low coordination oxides and oxynitrides in the subsurface had been further oxidised and were intermediary compounds in the passivation process. Al and Y oxides were lost to the HCl electrolyte, in agreement with their respective Pourbaix diagrams. The film with 49 at.% N showed little to no change in the data due to its high porosity which led to the oxide being detected at all probed depths. The metal core level spectra revealed a preferential order in which nitrogen bonded with the different metals. Nitrogen interacted first with Y, then Zr, then Al and Nb, and lastly Cr as the nitrogen content was increased.</p>