Single-track geometrical characteristics under different energy input and mass addition in coaxial laser cladding

Abstract

To provide a broad processing window with a high deposition rate, a comprehensive analysis of single-track geometrical characteristics over a wide range of laser energies and mass inputs in laser cladding is necessary. The formation of a single cladding track of Inconel 718 on a substrate by coaxial laser cladding, with a wide range of laser power from 1 200 W to 3 900 W and a powder feeding rate from 5 g/min to 35 g/min, was studied from both theoretical and experimental points of view. A quantitative model of powder concentration distribution was developed based on the powder transport morphology obtained by high-speed photography. Linear regression models were established between nine geometrical characteristics and the combined process parameters of laser power and powder feeding rate, written as P^αF^β, to quantitatively analyze the geometrical characteristics of the clad. These were confirmed by large correlation coefficients and analysis of residuals. From the findings we deduced that more energy input enhanced the outward direction of Marangoni convection, leading to the melt pool undergoing evolution from shallow dilution and flat dilution to fluctuating dilution. An almost linear relationship was found between the cladding width, W, and the laser power, indicating that laser energy accumulation was a major factor in the evolution of W. The increase ratio of the cladding height, h_c, ranged from 640% to 360% along with an increase in the powder feeding rate, implying that the evolution of h_c, was dominated by the powder feeding rate. The total area of the cross-section, A; the area of the clad, A_c; the area of the molten substrate, A_m; the total height of the cross-section, H; the penetration depth, h_m; the dilution ratio, D; and the wetting angle, θ, were determined by a complex coupling of energy input and mass accumulation, and they are proportional to P^0.5F^0.2, P^0.2F^0.5, P^0.5/F^0.2, P^0.3F, P^0.5/F^0.2, P^0.2/F^0.2, and P^0.2/F^0.2, respectively. This research aims to provide general knowledge on the influence of energy input and mass addition on the geometrical characteristics of the clad and its related influence mechanism. Such information could provide a reference and basis for promoting the practical application of laser cladding technology.