The laser-induced formation of superhard structures and phase transformations of carbon in the near-surface layer of cast iron

Abstract

Superhard structures with a microhardness of (2–5)×1010 Pa formed in the near-surface layer of gray iron covered by a thin copper inductor and processed by laser radiation are experimentally studied. The copper favors the formation of globular (or even spherical) carbon and stimulates the saturation of the near-surface layer of iron by carbon. The elemental analysis is performed, and the Raman spectrum from carbon globules is recorded. Based on this spectrum and the spectra from other carbon structures, the author argues that the laser processing converts the graphite of the near-surface layer to pyrolytic carbon, which offers a high hardness. A possible mechanism behind this process is discussed.