Investigation on direct laser powder deposition of 18 Ni (300) marage steel using mathematical model and experimental characterisation

Direct laser powder deposition (DLPD) is a laser process that can produce fully dense components from powders for production and repairing purposes. Marages are high-strength steels that are hardened through ageing treatment. This work presents a study which integrated the numerical and experimental approaches, for the evaluation of the properties of 18 Ni (300) laser deposited marage powder. The powder was deposited onto AISI 304 substrate by a CO2 laser. During the experiments, laser power, scanning speed, powder flow rate and degree of overlapping varied according to a Taguchi plan. In particular, the degree of overlapping between adjacent layers and between successive tracks was calculated using an analytical model. Density, porosity, dilution, microstructure, adhesion to the substrate and microhardness of multilayer samples were evaluated using statistical algorithms. Both clad-substrate and clad-clad interfaces were characterised by metallographic and SEM analysis. High-density samples, with a satisfactory level of porosity, for successful additive and part repair applications, were fabricated through the method proposed and characterised in this paper.