Mössbauer study of Ti-implanted 52100 steel

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Abstract
Information on phase transformations, solid solution alloying, compound formation, and residual stresses resulting from Ti implantation of AISI 52100 steel is obtained using 57Fe Mössbauer spectroscopy. Results show that Ti implantation reduced the near-surface (0.1 μm) retained austenite content by about 70% or more and evidence is found for an implantation-induced strain field which extends much deeper than the Ti-implanted zone. Changes in the near-surface martensite Mössbauer resonance are attributed to Ti on substitutional sites. Neither of the intermetallic compounds Fe2Ti or FeTi, nor the amorphous Fe–Ti or Fe–Ti–C phases are unambiguously detected. However some features of the data are not explained by Ti and/or C solid solution alloy analysis and this leads to suggestions for a≲10-nm-thick amorphous phase layer and surface oxides/carbides. The microstructural modifications are correlated with tribological properties measured on the same specimens. Improvements are attributed to the retained austenite reduction, residual compressive stresses in the near-surface layer, and the surface compounds.