Manufacturing Breakthrough

Siemens 3D-prints a turbine blade

By Tom Gibson

As a form of additive manufacturing, the process of 3D printing has been used to build myriad plastic prototype parts to serve as a model to show a design’s fit and form. But never has a 3D-printed part been subject to actual use under extreme conditions.

Until now. Siemens, the global giant specializing in infrastructure, transportation, energy, and manufacturing, has 3D printed a gas turbine blade and put it through the paces of a turbine operating at high temperature, pressure, and centrifugal force. And the blade has held up.

Typically, blades for gas turbines are investment casted, both for prototyping and production. The process requires building a mold for each blade, a complex, time-consuming, and costly procedure. Additive manufacturing (AM) eliminates that in the prototyping phase.

The printed turbine blades were produced from a high-temperature-resistant, powdered polycrystalline nickel-based superalloy. AM applications involve applying one thin layer of material after another to build up a shape, working off a CAD file. The main difference with Siemens’ blade process is that a laser beam is directed at each layer of metal powder, heating and melting it.

Christoph Haberland, an engineer and expert in AM for Siemens in their in Berlin, Germany facility, says, “It was a big success in proving that we can 3D-print parts that run on the machine. To our knowledge, nobody has tried this before.”

Haberland points out the main advantage of 3D printing turbine blades: “When you go with the conventional procedure, casting a design and testing it, this is a long lead time, and by using 3D printing, we could reduce it by 75 percent.” The team reduced the time from the design of a new gas turbine blade to its production from two years to two months.

The project team was an international one consisting of Siemens engineers and experts from Material Solutions in Lincoln, England, a company Siemens later bought. Besides Haberland, another prominent member was Jenny Nilsson, group manager for the design of AM parts in Siemens’ Finspong, Sweden plant. The core team numbered15 to 20 people, but others were involved including experts in simulation methods, heat transfer testing, and materials. Tests were conducted at what is now the Siemens test center for industrial gas turbines in Lincoln.

Nilsson has a master’s of science degree in mechanical engineering with a focus on heat transfer and fluid dynamics. Haberland has a PhD in mechanical engineering focusing on materials science and works in the business unit of large gas turbines.

“We started with an idea, and the vision was to print blades with different new designs and test and validate them in an engine.” Nilsson recalls. From there, the project went through several stages. Team members developed better cooling designs to improve the gas turbine efficiency, designed the blade, and developed the whole manufacturing process to manufacture this type of component and geometry. “The whole purpose was to create an approach to rapid prototyping.”

The turbine blades are typically placed in 450-megawatt gas turbines used in mechanical drive applications or power generation. Mechanical drive units might turn a pump for oil or a compressor for gas in a pipeline, as examples.

At full power, turbine blades rotate at 13,600 rpm with a blade tip speed of 480 meters/second and carry loads of 11 tons. The blades must also withstand tremendous heat because they’re surrounded by 1,250C gas when the turbine is in full operation. For project testing, the turbine blades were installed in a 13-megawatt (MW) SGT-400-type industrial gas turbine.

Will 3D printing go beyond prototyping and be used for production blades? Haberland replies, “The 3D-printing processes available today aren’t that efficient. So once you have developed the design and printed it for blades, parts will be casted. However, we are developing new 3D printing technologies, and we may end up being able to produce blades by 3D printing in the future.”

Based in Milton, PA, Tom Gibson, P.E. is editor and publisher of Progressive Engineer, an online magazine and information source (www.ProgressiveEngineer.com).