Welded Impeller Design
In the past, impellers consisted of a two- or (more commonly) three-piece riveted design. The latter incorporated a disc, separate blade, and cover. The blade was riveted to the disc by assemblers, and a cover was then riveted to the blades. This method resulted in inconsistent blade placement and numerous stress concentration points. (Two-piece riveted impellers offered a slight advantage compared to the three-piece design; however, the riveting process often caused rough surfaces and still exhibited the same stress points as the three-piece design.)
Today, vacuum furnace the accuracy and quality of the impeller manufacturing process have substantially improved. We use advanced manufacturing technologies and proprietary E-Braze welding, along with fillet and slot welding. E-Braze Technology An example of an impeller that has been welded using E-Braze.
E-Braze welding combines two proven methods; electron beam welding and vacuum furnace brazing – to create a weld joint with superior fatigue strength characteristics. Electron beam welding directs a beam of high-velocity electrons to the materials being joined, and the two pieces are essentially melted together. Furnace brazing uses a non-ferrous filler material to join two pieces of metal. The components are heated and joined together as the filler material cools.
In the E-Braze process, to fuse the impeller cover and blades, an electron beam weld is directed through the cover and a braze alloy foil to each blade. Fusion occurs across the complete cover-to-blade interface. During cooling, the foil in the weld area forms a smooth radius, minimizing the risk of stress concentration. The result is an impeller with greater reliability, longer life, and more accurate performance. The E-Braze welded Impeller is completed with a Hot Isostatic Pressing , or HIP process. This process uses an argon atmosphere or other gas mixtures heated up to 3000 degrees Fahrenheit (1650 Celsius) and pressurized up to 6895 bar (100,000 psi). This homogenizes the surface grain structure of the components, post-weld, to create a strong bond and remove internal voids, resulting in a reliable, long lasting impeller.
Edited by Eric
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