TEM investigation of tribo-oxide particles

DARJA JENKO; W. R. TUCKART; N. FOCHEZATTO; H. SVOBODA; A. JUAN; M. JENKO

Dubrovnik, Croacia.

Congreso; 14th Joint Vacuum Conference, EVC-12, 12th European Vacuum Conference, AMDVG-11, 11th Annual Meeting of the German Vacuum Society, CroSloVM-19, 19th Croatian-Slovenian Vacuum Meeting; 2012

Croatian-Slovenian Vacuum Society

Two series of tribodebris samples of Nb-Ti microalloy steel were analyzed in details by means of conventional and high-resolution transmission electron microscopy (CTEM and HR TEM) to find differences in morphology and composition of tribo-oxide particles. The first series of specimens were untreated material and the second series were the material with 25 % of martensite phase, treated at 810 oC (critical annealing temperature). Both series of the specimens were obtained from reciprocanting tribology test according to ASTM G133 and made at 5 N of normal applied load. Correct indentification of iron oxides present in the samples is important in order to identify the oxidation conditions and its influence on wear rate developed during the sliding process. According to the results of chemical composition analyses obtained by means of energy dispersive X-ray spectroscopy (EDS) the approximate temperature range during the tribology test could be estimated. The presence of different oxides (FeO, Fe2O3 and Fe3O4) could help to evaluate this temperature range and understand the wear rate due to of microstructure difference. We performed EDS analyses on different areas of the same particle and also on different particles. The analyses showed there are probably all three previously mentioned iron oxides present and also some other different ratios of iron to oxygen. Scanning transmission electron microscopy (STEM) analyses using bright-field (BF) detector were performed as well. The distribution of iron and oxygen in some particles is shown on EDS elemental mappings, line profiles and line analyses. The results of line profiles and line analyses showed that the composition in the majority of chosen particles is not the same through the whole volume.