Wettability of Sn alloys at metal interfaces: Metal surface treatment, interfacial temperature control and elemental modification

Controlling the wettability of metal surfaces has been extensively studied in advanced fields such as biomanufacturing, metalworking, and aerospace, which determines interfacial properties such as corrosion resistance and heat transfer efficiency. Wettability is primarily determined by the physical and chemical properties of the metal surface, but can also be influenced by ambient temperature, surface morphology, and chemical composition. In this study, the surfaces of various metallic substrates (Ti6Al4V, 304 stainless steel, Inconel 718, aluminum, and copper) were polished, textured with a femtosecond laser, and surface coated. The wettability of Sn alloys (Sn-0.7Cu and Sn-0.7Cu-10Zn) on different metal surfaces was investigated within an appropriate temperature range and evaluated in terms of high-temperature contact angle (HTCA). The wettability of the alloy surface exhibits a tendency to decrease with increasing temperature. After polishing, Sn alloy exhibited the lowest HTCA of 102.41 degrees on the copper substrate. Following femtosecond laser texturing, metal substrates with laser included laser-induced periodic surface (LIPSS) texture pattern demonstrated better wettability than those with a micro-pits texture. When the femtosecond laser exposure was 500, the HTCA of Sn-0.7Cu alloy on a Ti6Al-4V alloy with a LIPSS texture (115.7 degrees) was reduced by 5.9 % and 17.2 % compared to the polished surface (122.9 degrees) and the surface with a micro-pits texture (139.6 degrees), respectively. The addition of zinc to the Sn alloy significantly impacted the wettability of the 304 stainless steel substrates. The HTCA decreased by 7.6 % on the polished surface for the Sn-0.7Cu-10Zn alloy (116.8 degrees) compared to the Sn-0.7Cu alloy (126.4 degrees). Notably, the HTCA of the Sn-0.7Cu-10Zn alloy on the 304 SS substrate surface was as low as 12.33 degrees when a Sn alloy coating was applied. In conclusion, the effect of modulation of wettability was realized in specific cases through various metal surface treatments in this work.