GE (NYSE:GE) researchers recently announced the use of a process called “cold spray,” in which metal powders are sprayed at high velocities to build a part or add material to repair an existing part. Cold spray is part of GE’s expanded additive manufacturing toolkit. GE researchers are developing new ways to repair and even build up parts using cold spray, or as GE calls it, “3D Painting.”
Anteneh Kebbede, managerof the Coating and Surface Technologies Lab at the GE Research Center said, “In addition to being able to build new parts without welding or machining, what’s particularly exciting about cold spray as an innovative 3D process, is that it affords us the opportunity to restore parts using materials that blend in and mirror the properties of the original part itself. This extends the lifespan of parts by years, or possibly by decades, ultimately providing improved customer value.”
In an effort to gain a better understanding of cold spray technology advancements at GE, we connected with Anteneh Kebbede to share his thoughts and observations regarding the additive manufacturing technology in an AMazing® exclusive Q&A session.
AMazing®: Thank you for participating in this interview. The additive manufacturing technology cold spray is fascinating. When did GE Global Research first begin working with the technology?
Anteneh Kebbede: Cold spray as a coating technology was developed in Russia in the mid-80’s – by accident. At GE Global Research, we began to develop this technology in the 2010 timeframe and have continued to advance it by exploring its usage for a variety of alloys of interest to GE. Cold spray system design is advancing rapidly and we continue to leverage those tools to refine our process.
AMazing®: Would you please explain the basic process of 3D Painting?
Anteneh Kebbede: Explained simply, with 3D painting, we propel metal powders at a very high speed using high pressure gases, and spray them onto a substrate. The impact velocities are on the order of one kilometer a second – way too fast to see with the naked eye. The kinetic energy stored in the particles is sufficient to deform and locally heat the contact surface between the powder particles and the substrate to a point that a metallurgical bond forms between the particles and the substrate.
AMazing®: What qualifies a part as a good candidate for 3D Painting?
Anteneh Kebbede: The answer to that question is dependent upon a number of factors – its use environment, geometry, material it’s made from, and cost/benefit analysis. Generally speaking, if a part has come back from service and rebuilding only a portion of it may restore it close to its original state, it could be a good candidate for repair via 3D painting.
AMazing®: What advantages does cold spray offer over thermal sprays like plasma, flame, arc and others?
Anteneh Kebbede: That’s a tricky question to answer. A broad generalization that says cold spray is better than these other technologies would be inaccurate. Each process has its own distinct advantages for specific applications that it’s commonly used for, so in many instances, replacing one of these technologies with cold spray may not be the right approach. On the other hand, cold spray does create new possibilities for 3D painting because of the metallurgical bonding that’s formed during the process, the result of which could be used for repair or new component fabrication.
AMazing®: Is cold spray research limited to metals and/or metal-ceramics? Are superalloys being evaluated?
Anteneh Kebbede: GE is evaluating cold spray technology for metals, that is, alloys of interest to GE. We are developing the process for a number of alloys that are relevant to GE’s applications.
AMazing®: How thick of a free-standing structure can be formed? Are support structures required?
Anteneh Kebbede: At this point we cannot say what the thickness limit is. We have established that we can build structures that are much thicker than what is typically deposited by other conventional thermal spray processes. Typically, a support structure is needed to start building the desired product. The support structure may or may not remain as an integral part of the final product of the process.
AMazing®: How large a structure can be formed?
Anteneh Kebbede: Technology like 3D painting gives us new options. The complexity of the geometry of the structure or component will likely determine the size limit of what can be formed. The simpler the geometry the larger the limit is likely to be.
AMazing®: Are the powder coatings similar to the substrate in terms of material composition? Are the mechanical properties of 3D Painted coatings similar to the substrate?
Anteneh Kebbede: The answers to these questions are highly dependent upon the specific application involved. For example, when the intention is to repair local damage on a component, the goal would be to match the composition and properties of the deposited material with the substrate.
AMazing®: For high wear parts, how often may a part be 3D Painted?
Anteneh Kebbede: It’s really application specific. If the underlying structure hasn’t changed, theoretically, you could replace the worn area over and over. However, if something else changes in the bulk material besides what’s damaged, other options for repair or replacement may be considered.
AMazing®: Is post processing necessary?
Anteneh Kebbede: This, again, depends on the specific application and the materials involved. Some cases require post-processing while others may not.
AMazing®: If someone is interested in a career in additive manufacturing, what types of skills, education and/or training are needed?
Anteneh Kebbede: Most of the engineering disciplines could provide a solid background, although a combination of training in material science and mechanical engineering could be advantageous. Experience in the use of lasers for material processing, experience in rapid prototyping, thermal spray experience, and background in materials selection and processing (metallurgy, ceramics, and polymers) should all help in preparing one for a career in additive manufacturing.
AMazing®: Finally, what technical advances in 3D Painting do you envision five years from now?
Anteneh Kebbede: At GE, we believe in this technology and are excited to play a critical, innovative, role in its advancement. We view 3D painting as a key component in our additive manufacturing toolkit, along with technologies like 3D printing, and laser welding. As mentioned, cold spray system design is rapidly evolving, and GE is well-positioned to utilize the technology in the years ahead. So, stay tuned!
This concludes our interview. Thank you very much Anteneh for your participation and bringing awareness of GE’s exciting progress in cold spray; as a part of GE’s expanded additive manufacturing toolkit.
About Anteneh Kebbede
Anteneh has been at GE Global Research for over 14 years. Prior to becoming a lab manager in 2011 he either led or contributed to several materials and materials processing development programs for different applications. Examples of technologies Anteneh worked on include ceramic matrix composites, ceramic armor, solid oxide fuel cells, and advanced Sodium batteries. Anteneh holds a PhD in Materials Science and Engineering from the Pennsylvania State University, a MS in Metallurgical Engineering from Queen’s University, and a BSc in Mechanical Engineering from Addis Ababa University.
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