Blisk Repair with Laser Directed Energy Deposition

A blisk (bladed disk) is a turbomachine part that is composed of a rotor disk and blades. The distinctive characteristic of a blisk is that the blades are directly machined into the disk instead of being assembled. Due to its manufacturing cost, that ranges from $180.000 to $250.000, and the associated lead times, blisks are susceptible to be repaired.

On the other hand, Laser Directed Energy Deposition (LDED) is a process that allows the repair of high added-value parts (such as blisks) due to its (i) low and localized heat input, (ii) low thermal distortions, and (iii) small heat affected regions.

In this work, we address the restoration of the leading edge, the trailing edge and the tip of the blades of a blisk using LDED. These regions of the blades are worn out due to oxidation and particle erosion. We selected Inconel 718 as the powder material to use in the repair process, due to the harsh working environment of the blisk. The focus of this work is twofold. Firstly, the automation of the toolpath generation, as the blisk geometry is challenging and prone to collisions between the part and the nozzle head. Secondly, the process and material characterization, as porosity should be kept under control.

We test our methodology with the repair of a blisk of dimensions 600mm in diameter and 60mm in width made of F-114 steel. The metallographic cross-sections on the restored blisks show minimum porosity and no cracking. These results obtained proof the feasibility of using powder-based LDED for the repair of turbomachinery components using Inconel 718. Moreover, we are planning to integrate ultrasonic and X-ray inspections in further studies for a whole process-inspection automation that would pave the way to achieve certification with different OEMs.