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Hot Isostatic press
- Thread starter 123Dog
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The Hot Isostatic Pressing process is applied to the finished solid part. Under the effect of high pressure ~15000 psi and high temperatures the density of the part is increased by closing of voids. It is used on cast turbine blades among other parts. The process is also be used to process powder metallurgy parts. I believe Bodycote have a division which specializes in this process and you might find additional information on their web site.
There are a few methods of hot isostatic pressing (or HIPing) powder metals. The most common goes like this:
1. A powder part is pre-sintered, or a fabricated "can" is filled with powder, usually under inert gas protection.
2. The can is placed in an autoclave which is backfilled with argon.
3. Heating elements inside the sealed autoclave heat up the argon and the can.
4. As the can warms up, it reaches near melting point, or the "mushy zone". The argon is also heating up and, as you know, when a gas is heated in a confined space the result is pressure increase. (This is assisted by high pressure gas injection into the autoclave).
5. Since the "can" has spaces in it (between powder particles) the pressure of the gas uniformly squeezes the powder closer together, resulting in a [nearly] fully dense "compact".
Here's a decent overview:
I'm not fully familiar with HIPing castings, but it is a fairly common procedure to remove porosity.
1. A powder part is pre-sintered, or a fabricated "can" is filled with powder, usually under inert gas protection.
2. The can is placed in an autoclave which is backfilled with argon.
3. Heating elements inside the sealed autoclave heat up the argon and the can.
4. As the can warms up, it reaches near melting point, or the "mushy zone". The argon is also heating up and, as you know, when a gas is heated in a confined space the result is pressure increase. (This is assisted by high pressure gas injection into the autoclave).
5. Since the "can" has spaces in it (between powder particles) the pressure of the gas uniformly squeezes the powder closer together, resulting in a [nearly] fully dense "compact".
Here's a decent overview:
I'm not fully familiar with HIPing castings, but it is a fairly common procedure to remove porosity.
- Thread starter
- #5
Hip'ing of castings is common and may increase you chance of making a casting vacuum tight. We just completed a project for Princeton Univ on casting some vacuum vessels, since these were thin walls HIP'ing was not vey useful. You must have a sound skin on the casting for HIP to work.
Large castings can be made to hold vacuum, just need to engineer it up front with some casting computer modeling and if thick enough HIP should be beneficial, Let me know if you need any more help.
Bob Dzugan
Large castings can be made to hold vacuum, just need to engineer it up front with some casting computer modeling and if thick enough HIP should be beneficial, Let me know if you need any more help.
Bob Dzugan
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