Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization

• Published in: Applied physics. A, Materials science & processing Materials science & processing, 2018-04, Vol.124 (4), p.1-10, Article 326
• Main Authors: Kirner, S. V., Slachciak, N., Elert, A. M., Griepentrog, M., Fischer, D., Hertwig, A., Sahre, M., Dörfel, I., Sturm, H., Pentzien, S., Koter, R., Spaltmann, D., Krüger, J., Bonse, J.
• Format: Article
• Language: English
• Subjects: Applied physics; Characterization and Evaluation of Materials; Condensed Matter Physics; Conditioning; Femtosecond pulsed lasers; Heat treatment; Indentation; Laser beam heating; Laser processing; Lasers; Machines; Manufacturing; Materials science; Nanotechnology; Optical and Electronic Materials; Optical microscopy; Physics; Physics and Astronomy; Processes; Pulse duration; Pulse repetition rate; Sapphire; Spectroellipsometry; Surfaces and Interfaces; Thin Films; Titanium; Titanium oxides; Tribology
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-018-1745-8

Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.