Additive manufacturing and repair experts at Siemens Energy have developed the HybridTech solution to upgrade turbine blades, instead of just repairing them, via laser powder bed fusion (L-PBF). Specifically, it is now possible to implement cooling structures in critical areas to prevent blade tip failure.
While metal powder fed fusion processes (such as laser metal DED) are commonly used for part repair and upgrades (via laser cladding), it is much more complex to use powder bed fusion to add or modify features on an existing metal part. That’s because the laser head needs to have a very clear and precise vision of each of the parts it needs to work on, inside the powder bed.
By applying Laser Powder Bed Fusion (L-PBF) metal printing on an existing component, Siemens Energy was able 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.
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 the 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.
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, which Siemens defines as Hybrid L-PBF Repair (short: HybridTech). It requires the ability to seamlessly shift from physical to virtual and back to physical representations of a part in order to apply new modifications to a deteriorating existing component. Ultimately, 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 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.