Abstract
Pores and weak bonding are the inherently drawbacks for thermally sprayed coating. Laser beam is an attractive approach to remelt thermal spray coating for obtaining fully dense coating with metallurgical bonding with substrate. However, defects of holes or cracks are highly inevitable with unmatching remelting processing parameters. In this work, a thermally sprayed Cr3C2-NiCr cermet coating by high velocity oxygen fuel spraying was post-processed by laser remelting with a series of varying beam energy densities from 37.5 J/mm2 to 225 J/mm2. The defect evolution was investigated by both experimental and numerical simulation methods. Large holes and through-thickness cracks were typical defects observed in the remelt coating by optical microscopy. The experimental results show that remelting-induced defects evolve into three stages with laser energy density. The effect of energy density on remelt structure was further verified with the temperature field by numerical simulation with ABAQUS code. The stress field interpreted the crack formation at periodical formation sites. The results on the defect evolution shed light on obtaining functional coatings for industrial applications.
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