*2.1. Materials*

Samples of 15 steel, 25 steel, 35 steel, 45 steel, and 55 steel with carbon content of 0.15%, 0.25%, 0.37%, 0.45%, and 0.58%, respectively, were selected. The matrix samples are represented by A1, A2, A3, A4, and A5, respectively, and their chemical components are shown in Table 1. Laser biomimetic samples are represented by LR-A1, LR-A2, LR-A3, LR-A4, and LR-A5.


**Table 1.** The compositions of the samples (wt.%).
