Effect of heat input on martensitic stainless steel laser clad characteristics on ductile cast iron

Abstract

Laser cladding is a surface modification technique used for repairing and enhancing substrate materials by depositing powder layers with a laser beam. This study investigates the effects of laser power, scanning speed, and heat input on the porosity, microhardness, microstructure, residual stress, and thermal behavior of Metco 42C martensitic stainless steel powder deposited on FGS600-3A ductile cast iron used in sheet metal forming molds. Characterization was conducted using optical microscopy, SEM, EDS, digital image processing, thermal imaging, and residual stress measurements via XRD and ESPI methods. The cladding zone exhibited a columnar dendritic martensitic structure, with coarser dendrites observed at high heat input (316.67 J/mm) compared to low heat input (78.57 J/mm). Increased heat input significantly affected porosity, with pore formation mechanisms including gas entrapment, lack of fusion, balling effect, and thermal contraction. Microhardness variation was attributed to carbon diffusion from the substrate, with a peak hardness of 946 HV0.05 in the transition zone. Residual stress analysis revealed compressive stress dominance at high heat input and tensile stress at low heat input. Thermal analysis indicated a peak temperature of 1771 degrees C in the first cladding layer, which also exhibited a higher risk of cracking. These findings highlight the influence of heat input on the mechanical and microstructural properties of the cladding, providing insights for optimizing laser cladding processes in industrial applications.