In Metalaser Laboratory, we have pioneered a restoration process for damaged High-Pressure Turbine (HPT) blades in aero gas turbine engines. Leveraging Laser Directed Energy Deposition (L-DED), our method involves using a laser beam to forge a robust metallurgical bond between the machined surface of the damaged part and filler metal, adhering to on-the-shelf and new blade specifications. The process on the blades underwent rigorous testing through Finite Element Method (FEM), and the resulted microstructure of the added layers was investigated by Optical Microscopy (OM).
Research Highlights
- The aerospace industry grapples with the escalating challenge of aero-turbine blade repair, necessitating advanced processing methods.
- Laser Directed Energy Deposition (L-DED), a proven additive manufacturing technique, guarantees high-quality deposition with minimal heat input precisely at the damaged areas of the blades.
Challenges
Turbine blades, integral to gas turbines, endure extreme high-temperature and high-pressure conditions. To withstand such harsh environments, they are crafted from costly materials like Ni-base superalloys, renowned for durability and high-temperature resistance. However, the intricate manufacturing processes and high material costs create challenges, emphasizing the critical necessity for efficient repair and refurbishment solutions as an alternative to costly replacements.
Our Solution
Utilizing the L-DED method for the restoration of aero-turbine blades guarantees minimal heat-affected zones (HAZ) and improved microstructure in the deposited layers, while preserving the microstructure of the base metal. However, achieving these outcomes necessitates a profound understanding of working conditions, desired mechanical characteristics, base metal microstructure, HAZ, and the repair-added metal. Optimizing parameters for the laser additive manufacturing process is crucial. Therefore, the initial step involves a meticulous analysis of the blades within a simulation environment.
Pre-processing phase
A comprehensive procedure was devised for the analysis of blades in their demanding operational conditions, as outlined in Figure 2 for enhanced clarity and understanding.
Using the simulation, the fatigue and creep analyses of Nickle-based superalloys for the 7 types of V2500 blades have been predicted as shown in Figure 3.
Figure 4 was utilized to investigate the microstructure of various blade locations, guiding the selection of suitable parameters and precautions for the effective repair of the blades in alignment with their specific microstructural characteristics.
Microstructure analysis in Figure 4 was performed using Scanning Electron Microscope (SEM), Field Emission Scanning Electron Microscope (FE-SEM), and Optical Microscope (OM), and the possible failure mechanisms identified. Some post processing steps are mentioned in the next section.
Post-processing phase
Several aero-turbine blades were repaired and some of them are depicted in Figure 5.
Distortion analysis was performed using ABAQUS software as is shown in Figure 6 to ensure the repaired blades meet all the geometrical tolerances after the process.
Figure 7 was instrumental in exploring the microstructure of the Heat-Affected Zone (HAZ), a critical analysis considering HAZ susceptibility to diverse loads experienced by the blades.
Outcomes
- Employing the laser additive manufacturing method, we successfully repaired multiple blades, establishing a systematic hierarchy of essential steps for efficient blade restoration.
- A total of 65 Tay 650 blades underwent repair and testing, meeting the specified metallurgical and mechanical criteria equivalent to those of both off-the-shelf and new blades.
Related publications
Experimental analysis of the physical parameter effect on the clad thickness of Steam Blade Turbine in laser cladding process
Saeed Marandi, Seyedeh Fatemeh Nabavi, Mohammad H. Farshidianfar, Anooshiravan Farshidianfar, Javad Jahanpour, Behrooz Beidokhti, Mohammad Shojaati
17th National and 6th International Conference of Manufacturing Engineering (ICME 2021)