Nanomechanical surface properties of co-sputtered thin film polymorphic metallic glasses based on Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu
Chijioke Raphael Onyeagba, Mirkhalaf Valashani, Hongxia Wang, Cameron Brown, Prasad Yarlagadda, Tuquabo Tesfamichael
Abstract
Metallic glasses are amorphous materials that have shown prospects in several applications including biomedical due to their superior and unique mechanical, tribological, and bioactive properties. New functional coatings of thin film polymorphic metallic glasses (Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu) were deposited by co-sputtering of constituents from high purity (99.9%) targets. The thin film metallic glasses were deposited on stainless steel 316 L (SS316L) and titanium alloy (Ti) substrates. Co-sputtering offers tuneable parameters (pressure, power, and time), which fosters high-quality polymorphic films of desired thickness and composition. Surface and nanomechanical properties of the films, including surface morphology, structure, mechanical, and tribological properties were investigated using SEM, AFM, XRD, XPS, nanoindentation, and scratch test. The coated substrates exhibit uniform nanostructured films with surface roughness in the range of 1.5 to 7 nm. The XRD spectra show a dominant amorphous glassy polymorphic feature on both substrates with crystallites size in the range of 65–108 nm. Nanomechanical characteristics of the films suggest high wear resistance with film adhesion strength ranging between 624 - 2159 µN and 2273 - 2978 µN on SS316L and Ti substrates, respectively. Overall, these polymorphic Ti-Fe-Cu, Zr-Fe-Al, and Zr-W-Cu nanostructured uniform films with low surface roughness and high adhesion on SS316L and Ti substrates are potential functional surfaces for biomedical applications.