Hybrid multi-objective optimization based on response surface methodology for laser-cladding repair and remanufacturing technology

High strength, high hardness, and high wear resistance are required for the remanufacturing of the pipe at the hinge joint of the aircraft fuel system through laser cladding. However, laser cladding is a non-equilibrium solidification process, and reasonable process parameter design is vital for the quality and performance of the repaired layer. This paper proposes a combined approach based on response surface methodology (RSM) and a multi-objective desirability function to optimize the design of process parameters in laser cladding-based pipe repair and remanufacturing technology. First, a quadratic regression model correlating input variables (laser power, scanning speed, powder feeding rate) with output responses (dilution and microhardness) was established through the central composite design in RSM. The correlation between each process parameter and the target response was thoroughly studied and quantified, while the accuracy and reliability of the model were evaluated through analysis of variance (ANOVA). Afterward, the multi-objective response was optimized according to the criteria of minimizing dilution rate and maximizing microhardness, and the optimal process parameters were obtained. Finally, a comparison of various mechanical properties between the repaired coating and the substrate was conducted to validate the testing model efficacy and the results of the multi-objective optimization. These results were utilized to guide the actual production of pipes. The results confirmed that the experimental results aligned closely with the RSM predictions, with an error margin of less than 8 %. The optimized coating exhibited a dense and uniform microstructure, showing minimal dilution. The microhardness of the coating was similar to 1.26 times that of the substrate. Notably, the coating exhibited outstanding wear resistance, with a low average friction coefficient of 0.81 and minimal wear weight loss (1.5 mg). The coating, with a tensile strength 99.8 % of that of the substrate, meets the stringent requirements for pipe repair. Finally, the hybrid multi-objective optimization method is universally applicable.