Al-Ti-W alloys deposited by magnetron sputtering: Effective barrier to prevent steel hydrogen embrittlement

Thin film represents a promising alternative for the protection of metallic structures against hydrogen embrit-tlement and corrosion degradation. Al-Ti-W coatings were deposited by magnetron sputtering technique using three pure metallic targets. Tungsten was incorporated in Al-Ti amorphous coating with different contents ranging from 0 to 17 at% by keeping a constant Ti/Al ratio at an average of 0.8. The deposition rate was calculated in order to obtain 4 um as an uniform film thickness. XRD, DSC and TEM analyses were performed to confirm the amorphous state of the coatings and to determine the glass transition temperature (T-g) and crystallization temperature peak (T-p) These temperatures were increased respectively from 423 degrees C and 595 degrees C to 490 degrees C and 665 degrees C with the increase of W concentration up to 17 at%. Corrosion resistance in a saline solution decreased with the increase of W content.The incorporation of W element induced an increase of the thin film hardness (H) and Young's modulus (Er) from 9 GPa to 9.35 GPa and from 117 GPa to 131,79 GPa, respectively. The surface roughness varied with the incorporation of W that strongly influenced the coatings' corrosion behavior. Chemical and electrochemical hydrogen charging techniques were performed to expose coated steels to hydrogen sources. W addition in the binary Al-Ti coatings strongly enhanced their resistance to hydrogen ab-sorption. The estimated total hydrogen content trapped in the coated steel during a cathodic polarization decreased with the incorporation of W.

Automated summary

The study demonstrates that incorporating tungsten in Al-Ti coatings can significantly enhance the hardness and corrosion resistance of thin films, while reducing their hydrogen absorption capacity, thereby improving their protective effects on metallic structures.