Achieving Ultralow Wear with Stable Nanocrystalline Metals

• DOI: 10.1002/adma.201802026
• Publication Date: 2018-06-26T06:50:35Z
• Authors: John F. Curry; Tomas F. Babuska; Timothy A. Furnish; Ping Lu; David P. Adams; Andrew B. Kustas; Brendan L. Nation; Michael T. Dugger; Michael Chandross; Blythe G. Clark; Brad L. Boyce; Christopher A. Schuh; Nicolas Argibay
• Keywords: Nanocrystalline material; Delamination

Recent work suggests that thermally stable nanocrystallinity in metals is achievable several binary alloys by modifying grain boundary energies via solute segregation. The remarkable thermal stability of these has been demonstrated recent reports, with many exhibiting negligible growth during prolonged exposure to near-melting temperatures. Pt-Au, a proposed alloy consisting two noble metals, shown exhibit extraordinary resistance wear. Ultralow wear rates, less than monolayer material removed per sliding pass, are measured for Pt-Au thin films at maximum Hertz contact stress up 1.1 GPa. This the first instance an all-metallic specific rate on order 10-9 mm3 N-1 m-1 , comparable diamond-like carbon (DLC) and sapphire. Remarkably, sapphire silicon nitride probes used experiments either higher or alloy, despite substantially hardness ceramic probe materials. High-resolution microscopy shows surface microstructural evolution tracks after 100k passes. Mitigation fatigue-driven delamination enables transition atomic attrition, regime previously limited highly wear-resistant materials such as DLC.