We report a composite coating on vermicular graphite cast iron reinforced with Al 2 O 3 particulates, processed by selective laser surface alloying, with the thickness of ∼600 µm and coverage fraction of 20%. The original microstructure was thus considerably modified. Different fractions of the Al 2 O 3 particulates were added, ranging from 5 to 25 wt-%. Microhardness and strength were both increased, due to the formation of the composite coating, which led to a series of strengthening mechanisms. In addition, in thermal fatigue test, the crack density was reduced, due to the surface composite coating and the particular scanning strategy. Cracking on the sample surface was effectively restrained by the composite coating.
In this work, the mechanical properties and microstructures of vermicular graphite cast iron processed by selective laser surface alloying with ultra-fine ZrO 2 ceramic particulates were investigated. A particulate-reinforced metal matrix composite coating with the thickness of *650 lm was fabricated by laser treatment on the sample surface. The particulates were uniformly distributed in the microstructure of the coating. The tensile strength and microhardness both increased with the particulate fraction, since more tensile load was transferred from the matrix to the reinforcement showing essential strengthening effect. The composite coating also sharply reduced the wear mass loss and thus improved the wear resistance.
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