Laser Melting of Prefabrication AlOOH-Activated Film on the Surface of Nodular Cast Iron and Its Associated Properties

Abstract

This study aimed to improve the absorption rate of laser energy on the surface of nodular cast iron and further improve its thermal stability and wear resistance. After a 0.3 mm thick AlOOH activation film was pre-sprayed onto the polished surface of the nodular cast iron, a GWLASER 6 kw fiber laser cladding system was used to prepare a mixed dense oxide layer mainly composed of Al2O3, Fe3O4, and SiO2 using the optimal laser melting parameters of 470 W (laser power) and 5.5 mm/s (scanning speed). By comparing and characterizing the prefabricated laser-melted surface, the laser-remelted surface with the same parameters, and the substrate surface, it was found that there was little difference in the structure, composition, and performance between the laser-remelted surface and the substrate surface except for the morphology. The morphology, structure, and performance of the laser-melted surface underwent significant changes, with a stable surface line roughness of 0.9 μm and a 300–400 μm deep heat-affected zone. It could undergo two 1100 °C thermal shock cycles; its average microhardness increased by more than one compared to the remelted and substrate surfaces of 300 HV, with a maximum hardness of 900 HV; and the average friction coefficient and wear quantity decreased to 0.4370 and 0.001 g, respectively. The prefabricated activated film layer greatly improved the thermal stability and wear resistance of the nodular cast iron surface while reducing the laser melting power.