Effect of air annealing on mechanical properties and structure of amorphous B4C films

• Published in: Surface & coatings technology Vol. 205; no. 16; pp. 4052 - 4057
• Main Authors: KULIKOVSKY, V, VORLICEK, V, CTVRTLIK, R, BOHAC, P, JASTRABIK, L, LAPSANSKA, H
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 15-05-2011
• Subjects: Amorphous structure; Annealing; Applied sciences; Bulk sampling; Carbon; Cross-disciplinary physics: materials science; rheology; Crystal structure; Exact sciences and technology; Hardness; Materials science; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Oxidation; Physics; Reduction; Stresses; Surface treatments; Raman spectra; Annealing; Amorphous B; Mechanical properties; Surface treatments; C films; Oxidation; Air annealing; Air; Hardness; Heat treatments
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2011.02.052

Amorphous B4C films were prepared by magnetron sputtering of the hot-pressed B4C target under different regimes. The effect of the annealing temperature on the hardness, intrinsic stress and film structure was investigated. Changes in the film structure and composition were investigated by Raman spectroscopy, confocal microscopy, and EPMA. Annealing at 500 C for 1 h led to stress reduction, a slight thickness decrease and increased film hardness. However, at 600 C film oxidation proceeded with the formation of boron oxide and amorphous carbon phases in the surface layer and the thickness of the film quickly decreased. Film oxidation was accompanied by the formation of numerous carbon hillocks and the redistribution of film material after annealing at 500 and especially 600 C. The oxidation of a-B4C films and crystalline bulk samples was a heterogeneous process, indicating the heterogeneous structure of the amorphous films and the bulk crystalline samples. Annealing in air for a long period delayed the formation of hillocks to 400 C and changes in film morphology to 300 C. Thus the upper temperature limit for a-B4C films in air depends on the exposure time at the operational temperature.