Effect of pulse laser parameters on the microstructure of the in-situ Fe-TiC hard layer: Simulation and experiment

Abstract

In the present study, the pulsed laser utilized to synthesize the in-situ Fe-TiC hard layer on carbon steel. In this respect, ilmenite, as an inexpensive raw material, was used for the first time in laser cladding. The effect of pulse parameters on the microstructure and hardness of the clad layer was investigated. The solidification of the weld pool was started in planar form and then transformed to columnar, dendritic, and finally lamellar eutectic. Thus, an appropriate structure with a high density of hard particles was obtained near the surface. The effects of laser scan speed and pulse duration on the evolution of the solidification structure were investigated. It was found out that the volume fraction of regions with different solidification modes can be adjusted. The properties of the hard layer can be manipulated in this regard. Increasing the laser scan rate from 1 to 5 mm/s reduced the thickness of the clad layer from 135 to 70 µm, while increased the fraction of the planar growth region from 7% to 46% of the clad thickness. Numerical simulation by finite element method was also implemented for better realizing the influence of parameters. To achieve this aim, the variations of temperature and temperature gradient were analyzed. The results revealed that the effect of the laser scan speed is more significant than the pulse duration. Eventually, 2 mm/s and 8 ms were defined as the optimized process parameters. The average hardness of the produced clad is improved eight times higher than the substrate.