Laser cladding of Inconel 718 with 75Cr3C2 + 25(80Ni20Cr) powder: Statistical modeling and optimization

Abstract

Laser cladding of Inconel 718 superalloy with 75Cr3C2 + 25(80Ni20Cr) powder was performed with a 400 W pulsed Nd:YAG laser using Response Surface Methodology. Laser frequency, pulse width, and scanning speed were considered as the input variables. The geometry of the deposited beads (width, height, and clad angle), dilution ratio, and hardness were considered as the output responses. It is found that the laser frequency and pulse width have a positive effect on the bead width, clad angle, and dilution ratio but a negative effect on the bead height and hardness. In contrast, the reverse effect is observed for the laser scanning speed. There is an opposite relationship between the hardness value and the dilution ratio. By increasing the dilution ratio, the concentration of chromium carbides in the deposited bead decreases, causing a drop in the hardness, compared to the condition with a low dilution ratio. The process optimization was performed by a simultaneous optimization technique. The laser frequency of 20 Hz, pulse width of 12.9 ms, and laser scanning speed of 5.43 mm/s are found to be the optimum parameters over the ranges investigated in this work. The average hardness value of the optimum sample is approximately 1050 Hv, about 2.5 times the value of the substrate (IN 718 in solution annealed condition). The clad zone of the optimum sample is mainly composed of chromium carbide (Cr7C3) and refined eutectic structure (γ + Cr7C3). The γ + Laves (δ) eutectic structure is formed in the partially melted zone of the optimum sample.