Scratch-Induced Deformation Behavior of Cold-Sprayed Aluminum Amorphous/Nanocrystalline Coatings at Multiple Load Scales

Abstract

Scratch-induced deformation behavior of cold-sprayed Al amorphous/nanocrystalline alloy coatings at multiple load scales is reported. Micro-scratch tests are carried out at several loads (1000-4000 μN) in constant and ramp loading conditions. Macro/high load scratch tests are carried out at 5 N load in ramp loading conditions. The deformation of as-sprayed and heat-treated coatings is analyzed in terms of scratch morphology, and friction. A lower coefficient of friction (COF) is obtained for as-sprayed coatings. Despite lower COF, as-sprayed coatings show a higher wear volume loss (4 times in micro-scratch and 1.4 times in macro-scratch) as compared to heat-treated coatings. Fluctuations were observed in COF along the scratch length of as-sprayed coatings in micro-scratch tests, which are correlated to the shear band formation. Higher scratch wear resistance is observed in the heat-treated coatings as compared to as-sprayed coatings due to denser microstructure with embedded intermetallic phases. Scratch-induced deformation behavior changed from the shear band dominated brittle mode in as-sprayed to plowing type in the heat-treated coatings.