Laser surface hardening of S45C medium carbon steel using ND:YAG laser with a continuous wave

The objective of this paper is to investigate hardening characteristics of S45C medium carbon steel in a laser surface hardening process using a high power Nd:YAG laser with a continuous wave. The laser surface hardening has been carried out using uniform beam technology. In the experiments using the uniform beam technology, the optical lens with an elliptical profile is designed to obtain a widely uniform beam profile and a large hardened area with a uniform hardness. From the results of the experiments using the designed optical lens, it has been shown that the maximum hardness and the width of the hardened area are approximately 780 Hv and 22.3 mm when the heat input capacity of the laser is 4.90 × 102 J/cm2, respectively. In addition, it has been found that the width of the hardened area and the hardness using the designed lens are three times larger than those using the defocusing technology.