Laser Strengthening of a Steel Surface with Fullerene Coating

Modification of a steel surface by coating with fullerenes C 60 and subsequent treatment by intense laser radiation has been investigated. The initial samples are made of low-carbon steel. The laser source is a commercial LTA4-1 laser with a wavelength of 1.064 µm, pulse energy up to 12 J, and pulse width of 2 ms. The obtained dependences of the surface microhardness on the specific laser energy are nonmonotonic with a maximum in the range of 100–150 J/cm 2 . An eight-fold increase in the surface microhardness can be reached under optimal treatment conditions. There is an increasing dependence of the degree of surface strengthening on the fullerene-coating thickness. In addition, the laser irradiation of the treated surface is accompanied by a decrease in the friction coefficient by several tens of percent. The experimental results are compared with the data of similar measurements for nanocarbon soot used as the coating, which was obtained by the electric-arc sputtering of graphite with subsequent extraction of fullerenes.