Laser Cladding Refurbishment of Directionally Solidified MAR-M-002 Turbine Blades with Inconel 625 Powder

In this study, IN625 powder was deposited on directionally solidified (DS) Mar-M-002 superalloy using a fiber laser cladding technique. The effects of laser parameters, namely laser power, scanning speed, and duty cycle were investigated on coating defects, microstructural evolution, dilution ratio, molten pool geometry, and microhardness. The results showed that increasing the heat input to 92.08 J/mm induced solidification cracking in the clad zone, whereas reducing it to 25.03 J/mm produced unmelted powder particle defects. An increase in scanning speed from 4.5 to 8.5 mm/s raised the thermal gradient (G) at the interface and transformed the solidification morphology from cellular dendritic to planar. Similarly, reducing the laser power from 400 to 325 W and lowering the duty cycle from 85% to 70% increased the G/R ratio and promoted a transition from cellular to planar at the interface. Furthermore, increasing the scanning speed, decreasing the laser power, and reducing the duty cycle resulted in a decrease in dilution ratio, clad width, clad height, and clad depth. The highest hardness, 388 HV, was recorded in the base metal due to γ′ precipitates. Increasing the scanning speed enhanced hardness in both the interface and clad regions, while lowering laser power and duty cycle produced a similar hardening effect.