Brazing in aerospace-connecting the world around us

Posted by Lucas-Milhaupt Brazing Experts on May 4, 2020

In our current era, connecting regions of the world has never been more important, whether it is bringing loved ones together, supplying disaster areas with immediate aid, or sending satellites into space. Incredible advancements in aerospace have allowed companies to meet these needs, but behind every airplane and inside of every jet engine, there are critical connections that help maintain the equipment integrity that we often take for granted. Many companies turn to brazing as the safe and secure solution to making these connections, ones that will last under extreme conditions and over many years of continuous service. But which parts exactly are brazed on an airplane? Why are certain braze alloys used over others? And just how important is it to produce a quality joint for aerospace components?

Of the many aircraft components that incorporate brazing, one of the most critical is the pitot probe. Evident to boarding passengers as they look to the nose of the aircraft, pitot probes are affixed to the plane to measure airspeed. With airspeed being such an important safety factor for planes, the integrity of the pitot probe is undoubtedly crucial. Brazing several smaller components of the probe assembly provides a robust product that will stand up to the various temperatures and pressures it will see while still providing a smooth enough joint that will not disrupt air flow or provide faulty readings to the pilots.

But with such a wide range of braze alloys available, how does one choose the correct product for the job? While a variety of corrosion resistant materials can be used for pitot probes, one of the most common base metals used is stainless steel. In order to help promote corrosion resistance after brazing, silver based alloys such as Lucas Milhaupt’s Silvaloy 505 (50Ag/20Cu/28Zn/2Ni; AMS 4788; AWS BAg-24) or Silvaloy 630 (63Ag/28.5Cu/6Sn/2.5Ni; AMS 4774; AWS BAg-21) are the products of choice due to their small nickel additions. This addition of nickel helps promote alloy wetting on the stainless steel surface while also helping to prevent interface corrosion. Additionally, both alloys can withstand the cyclic thermal cycles introduced by flying at different altitudes as well as provide strong, hermetic joints over the life of the probe.

Not all aerospace assemblies will see only a few hundred degrees at peak operating condition, however. Consider, for example, speed and torque sensors that are used to measure turbine speed. The sensors have to provide reliable information under high stresses and high temperatures. While silver alloys exhibit high strength in many applications, their decreased high temperature strength is a limiting factor when an application calls for service temperatures of up to 900F or more. In this case, Lucas Milhaupt’s gold-nickel braze alloy, Premabraze 131 (82Au/18Ni; AMS 4787; BVAu-4 Gr 1), is a work horse for high temperature aerospace applications. In addition to its ability to provide strong joints at elevated temperatures, Premabraze 131’s high purity and resistance to oxidation make it ideal for electrical connections as well as joints where corrosion resistance is key.

In the ever-growing realm of aerospace, hundreds of unique applications call for brazing to ensure sound connections and reliable product performance. Lucas Milhaupt proudly offers a vast selection of alloys, including gold, palladium, silver and nickel-based alloys as well as other specialty alloys to help meet your needs. In addition to being able to provide braze alloys in various forms such as specialty preforms, paste, wire, and strip, Lucas Milhaupt is also AS9100 certified meaning we supply only the highest quality products that will meet the most stringent of requirements. With the aerospace industry projected to be worth over one trillion dollars in the next twenty years, we understand the need for an industry partner to help set yourself apart in this increasingly important market. The Lucas Milhaupt technical team is always ready to support your application questions, so please reach out today!

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