Effect of Process Parameters on Pulsed-Laser Repair of a Directionally Solidified Superalloy

Abstract

Directionally solidified nickel-based superalloy GTD-111 was repaired using pulsed Nd:YAG laser powder deposition (PLPD). A test matrix was created and tested to link deposit and defect formation to process parameters. Epitaxial solidification of the deposit was achieved. The grain size was uniform throughout multiple layers of deposit and appeared to be of cellular dendritic morphology. The crack formation is associated with the ''stray'' grains, which seem to be controlled by the geometry and overlap of the deposits. The formation of stray grains tended to be suppressed in deposits with shallow and wide profiles with smooth toe transitions into previous beads. Geometric discontinuity and formation of stray grains were found to contribute significantly to the formation of microfissures at the weld toes. Multiple pulses were found to remelt and heal the microfissures in the previous spot deposit. With optimized process parameters, crack-free, multiple-layered, deposits were achieved for tip repair (topdown orientation) of GTD-111 blades with René 80 and IN625 filler metals.

Investigation of Microstructure and Mechanical Properties of the Repaired Precipitation-Strengthened Ni-Based Superalloy via Laser Melting Deposition

“…The laser melting deposition (LMD) technique is an advanced technique that utilizes laser energy to melt metal powder, enabling the gradual formation of components via layer-bylayer stacking [4,5]. This technique provides the advantages of low heat input and high material availability, as well as the ability to ignore the complexity of structure, which makes it well-suited for repairing damaged blades [6,7].…”