Additive Manufacturing Enables Advanced Blade Tip Repair and Upgrade

A new digital repair chain using “Hybrid” Laser Powder Bed Fusion makes it possible to add new features to gas turbine blades.

Additive Manufacturing and repair experts at Siemens Energy have developed a solution to upgrade turbine blades instead of just repairing them. Specifically, it is now possible to implement cooling structures in critical areas to prevent blade tip failure.

A single turbine blade of an SGT5-4000F gas turbine converts about as much power into rotational energy as 10 Porsche 911s. Due to the high temperatures coupled with the high gas velocities during operation of a gas turbine, burn-off at the blade tip can occur, ultimately leading to gap formation and a measurable drop in the performance of the entire turbine. This process leads to a vicious circle: with greater gap formation, the temperature of the blade material increases due to the overflowing hot gas, which in turn leads to even faster material loss and further increases the gap between blade tip and ring segment.

By applying Laser Powder Bed Fusion (L-PBF) metal printing on an existing component, it became possible to produce structures with inner channels in high resolution. This high resolution is important to incorporate the new cooling geometries with a very limited cross-section. With this new design, the critical areas can be cooled more effectively, thus preventing material loss.

Blades that have been in operation at high temperatures have individual shapes, making the L-PBF repair more challenging. Therefore, a new CAD-CAM chain was developed which automatically adapts the shape of the L-PBF tip to perfectly match each blade. By combining 3D scanning technologies and an algorithm developed by the Siemens Energy team, a digital repair chain was established that can morph the geometry parametrically. The team also had to develop the L-PBF process for an extremely oxidation-resistant material for the blade tip.

The application of this technology to existing components is still a rather unexplored marginal area of 3D printing technology, also known as Hybrid L-PBF Repair (short: HybridTech). Fact is: This innovation offers direct customer benefits through the constant power output of the respective gas turbine.

The first blade sets have already been manufactured and a conversion of the standard repair procedure to the new process is underway. The technology is to be applied to other components in the future and even completely new component designs can be upgraded with it.

Siemens Energy is a pioneer in additive manufacturing and uses the technology for rapid prototyping, repair and manufacturing as well as providing spare parts on demand. The company has also moved into serial AM production for dedicated applications such as pre-combustion swirlers for their SGT-8000H gas turbine. Through its subsidiary Materials Solutions – A Siemens Energy Business, the company also delivers high-end production parts for customers in the aerospace, automotive and other high-performance industries as well as trainings and engineering services.

The development of HybridTech is part of the research project “Change in production technology,” funded by the European Regional Development Fund. More information: https://wvsc.berlin/en/research-project-maintenance-repair-and-overhaul/

Source: Siemens Energy