Abstract. Nd-YAG lasers have been successfully used in recent years as reliable heat sources for surface modification of engineering materials such as laser surface re-melting. In the present study, X12 tool steel was surface modified by using the pulse Nd-YAG laser technique. Laser parameters are selected of 12 J pulse energy, 15 Hz frequency, 20 mm defocus length, 6 ms pulse duration, and 5.6 mm /s mm scanning speed. These parameters were chosen after undertaking trials to give suitable parameters in this process. Optical microscopy and backscattered scanning electron microscopy (SEM) with EDS and X-ray diffraction techniques were used to analyze the microstructure changes of the surface of tool steel. The wear resistance test was achieved by using a pin on disk method. The reason for this work is to improve the wear resistance for the surface layer of tool steel after changes the morphology of the structure by rapid solidification during laser re-melting. In general, the structure consists of the dendrite and cellular structures with ? ferrite formed under conditions of rapid solidification without the primary coarse carbides. After laser melting, the results of the structure at the surface layers show an increase in wear resistance.
Conclusions
1. Rapidly solidified layers of the surface X12 tool steel were obtained by Nd-YAG surface re-melting.
2. The main structure of the melted zone consists of cellular morphology with some dendritic structure. Defects -free observed in the melted zone.
3. Refinement in the microstructure and more uniform carbides were obtained that caused by high cooling rate and high-temperature gradient of laser process.
4. The wear resistance of the re-melted zone of X12 steel and an improvement in wear resistance of 74% higher than that of the as-received steel.