In the present study, hot work AISI H13 tool steel (0.4 wt% C, 0.4 wt% Mn, 5.2 wt% Cr, 1.5 wt% Mo, 1.0 wt% V, Fe balance) plates with dimensions of 100 mm×100 mm×12 mm in hardened (austenitized at 1030 °C for 10 min followed by gas quenching) and tempered (at 620 °C for 2 h) conditions were used as substrate. The surface of the substrate was mechanically polished (to a roughness level of 0.9 μm) and subjected to laser irradiation with a 6 kW continuous wave diode laser (wavelength ~915 nm) delivered through an optical fiber head mounted on a 6-axis Robot with a laser spot size of 20 mm×5 mm and about 285 mm working distance between the laser head and the substrate. Fig. 1(a) depicts the laser surface hardening and melting treatment process schematically. The laser beam used in laser surface hardening and melting was analyzed using LASERSCOPE UFF 100 (supplied by M/s Prometec GmbH, Germany) at focus. System is integrated with PROMETEC LASERMETER along with the beam absorber to measure power. Fig. 1(b) depicts the laser intensity distribution of the laser beam (20 mm×5 mm) at focus for an applied laser power of 2000 W. It is observed that the only 18 mm of the laser beam width showed more than 60% of laser energy density necessary for adequate heat input for melting/hardening. From this intensity distribution it can be concluded that the width of the melted/hardened zone can be smaller than the actual laser beam width (20 mm) due to this trapezoidal (near top-hat) intensity distribution profile along the width. Laser optic head was equipped with an optical pyrometer (MAURER, Series KTR 1475) to record online surface peak temperature of the processing zone. Laser processing was conducted using argon gas at 2 bar pressure as shrouding gas supplied using off-axis rectangular nozzle (with opening of 20 mm×4 mm). The main process parameters for surface hardening and surface melting were laser power and processing speed. The detailed parametric combinations used in the present study are summarized in Table 1. The laser energy density as mentioned in Table 1 is calculated using Eq. (1).