* If you are having trouble viewing this e-mail, click here.
* To make sure you continue to receive our e-mails in your inbox (not sent to bulk or junk folders), please add newsletter@vacaeronews.com to your address book. Click here for more information.
* At VAC AERO International Inc., we practice permission-based marketing. To unsubscribe, please click here.
* To log on to the VAC AERO web site, please click here.
|
 |
|
|
|
|
Why Heat Treat in a Vacuum?
|
 |
The air we breathe contains a number of elements that can react with metals under the proper conditions. Moisture, oxygen, carbon dioxide and hydrogen are present in significant amounts in our atmosphere. Each can react to varying degrees with many different metals. While many of these reactions occur to only a small extent at room temperature, they are often greatly accelerated in the presence of heat. Consider the example of a piece of polished metal held over a heat source. It will eventually turn blue or black as the elements in the atmosphere react with the hot metal. |
|
|
Eutectic Melting
|
 |
In vacuum processing, metal surfaces remain very clean and free of oxides. When these near-perfect surfaces are in contact with other surfaces, certain elements have a tendency to interact between the surfaces through solid state diffusion. Therefore, a major consideration when selecting both hearth and load fixturing materials for vacuum heat treating is the possibility of solid state diffusion between different materials in contact at high temperatures. Solid state diffusion of certain elements can cause the formation of a lower melting point alloy called a eutectic. For example, solid state diffusion between carbon and nickel can begin to occur at temperatures as low as 1165ºC (2130ºF) and cause local melting, also known as eutectic melting. |
|
|
Using Thermal Spray for Repair of Service-Damaged Parts
|
 |
Thermal spray processes like air plasma spray and High Velocity Oxygen Fuel (HVOF) are usually thought of as being used primarily for applying protective coatings to new parts. While new part applications do indeed constitute the majority of their use, there are also a wide variety of repair techniques that employ thermal spray processes. VAC AERO has been a leader in developing repairs for aircraft structural components and gas turbine engine parts using thermal spray processes. An example of a structural component repair involves a flap track from a popular turbo-prop aircraft. As the wing flaps of this aircraft are extended and retracted during landing and take-off, rollers run along the surfaces of a series of components known as flap tracks.
|
|
|
|
