Ultrafast laser-induced surface modification of Kanthal® AF: Morphology, chemistry, and wettability under ambient conditions

Ultrafast laser surface modification offers an attractive route for enhancing the functional performance of high-temperature alloys. However, research on ultrafast laser-induced modifications of Kanthal® AF remains limited. In this study, ultrafast laser ablation was employed to systematically investigate the influence of laser parameters on the surface morphology, chemistry, and wettability of Kanthal® AF. Surface features, chemistry and wetting behaviour were characterised using microscopy, spectroscopy, profilometry, and contact angle measurements. Laser processing resulted in the formation of laser-induced periodic surface structures and a progressive increase in nanoscale surface roughness with increasing laser fluence. The ablation rate increased with fluence, whereas the ablation efficiency decreased. SEM-EDX analyses of the near-surface bulk region indicated that fully ablated areas retained an overall alloy composition close to that of the polished substrate, with only minor Fe and Al depletion and a relative Cr enrichment. XPS revealed pronounced surface oxidation, characterised by enrichment of Fe- and Cr-based oxides, disappearance of metallic Fe, Cr and Al, and a fluence-driven transition from Cr 2 O 3 to CrO 3 . Raman spectroscopy, supported by XPS, confirmed the formation of mixed Fe-Cr-Al oxide phases dominated by α-Fe 2 O 3 . Contact angle measurements demonstrated a transition from a low hydrophobic polished surface (≈ 91°) to highly hydrophobic laser-ablated surfaces (>137°), with both fluence and hatching distance strongly influencing wetting behaviour. These findings demonstrate that ultrafast laser processing enables controlled modification of surface morphology and topography, oxide chemistry, and wettability of Kanthal® AF alloy, highlighting its potential for tailoring surface properties toward improved corrosion resistance and high-temperature performance. • Ultrafast laser ablation induces LIPSS and increases surface roughness on Kanthal® AF. • SEM-EDX shows bulk alloy composition is largely preserved after laser processing. • XPS and Raman reveal fluence-dependent formation of Fe-, Cr- and Al-based oxides. • Surface wettability is tunable, reaching highly hydrophobic states at higher fluence. • Ultrafast laser processing enables surface tailoring for high-temperature applications.