Effect of Overlap Rate on the Properties of a Martensitic Stainless Steel Laser Cladding onto Ductile Cast Iron

In this study, Metco 42C martensitic stainless steel powder was deposited on FGS600-3A ductile cast iron used in sheet metal forming molds. The effect of overlap ratio on the porosity, microstructure, microhardness, and residual stress was analyzed by optical microscope and digital image processing. The residual stress was measured experimentally using the XRD method. The results indicate that the interface microstructure between the coating and substrate reveals strong metallurgical bonding, evident as a narrow bright band and decarburization of the coating layer due to carbon diffusion. Epitaxial dendritic growth was observed, transitioning from coarse dendrites in the second layer to equiaxed grains in the third. Porosity rates, ranging from 0.75 to 4.35%, were significantly affected by the overlap ratio. The optimal overlap ratio (65%) minimized porosity (0.75%) and maximized microhardness (559.7 HV0.05) at a depth of 2100 mu m. However, an excessive overlap rate (80%) led to bonding problems and gully formation. XRD measurements indicated a correlation between overlap rates and residual stress patterns, with higher overlap ratios reducing tensile and compressive stresses across 0 degrees, 90 degrees and 45 degrees directions. These findings highlight the critical role of overlap rate in enhancing laser cladding performance and efficiency.