Multi-objective optimization for laser cladding refractory MoNbTiZr high-entropy alloy coating on Ti6Al4V

In this study, a novel MoNbTiZr refractory high-entropy alloy (RHEA) coating was synthesized on Ti6Al4V surfaces by laser cladding (LC) with different processing parameters. The mathematical models between laser processing parameters (laser power, powder feeding rate, scanning speed) and dilution, porosity, and microhardness were developed by response surface methodology (RSM) and validated by ANOVA based on singlefactor experimental results. The results show that the dilution and porosity of the coating are negatively correlated due to the significant difference in melting point between the Ti6Al4V substrate and the RHEA powder. The rise in the dilution causes a decrease in the content of the strengthening elements in the coating, which is the main reason for the sudden drop in the microhardness to 425 HV. Compared to laser power and powder feeding rate, the analyses of variance show that the scanning speed has a relatively high F-value of 70.38. Also, the dilution has a positive correlation with laser power and scanning speed, and is inversely correlated with the powder feeding rate. Finally, a multi-objective optimization in terms of dilution, porosity, and microhardness was performed, and the optimal combination of processing parameters was a laser power of 2700 W, a powder feeding rate of 8 g/min, and a scanning speed of 3 mm/s. The predicted results are in good agreement with the validation results.