Influence of process parameters on the catchment efficiency and geometric characteristics in laser metal deposition tracks for building thin-wall parts

This study investigates the influence of process parameters on catchment efficiency and geometric characteristics such as track height, track width, and wetting angle for low energy density inputs in the blown powder Laser Metal Deposition (LMD) process for building thin-walled parts or repair volumes. Initially, a pilot study was conducted to examine the process parameters that affect catchment efficiency and geometric characteristics, from which five different process parameters such as (i) Laser power, (ii) Carrier gas flow rate, (iii) Deposition speed, (iv) Stand-off distance, and (v) Powder feed rate were identified as parameters of significance to the study. The impacts of these process parameters on catchment efficiency and geometric characteristics were investigated experimentally, and the data were analyzed using ANOVA and Response Surface Methodology (RSM). An analytical model was developed to predict the catchment efficiency, which was validated through experimentation. A comparison was made between the analytical, empirical, and experimental models for catchment efficiency, and it was found that the error was less than 8% which shows relatively good agreement between the proposed and experimental measurements. Furthermore, an empirical-statistical method was employed to establish the relationship between the chosen process parameters, catchment efficiency, and geometric characteristics to fabricate a single continuous track. Based on these correlations, a process map was constructed to identify the optimal processing conditions to obtain a single continuous track of IN625 powder on SS304 substrate with a higher catchment efficiency. This study achieved a maximum catchment efficiency of 71% for a low-energy density input.