Motor Oil In A Vacuum 2

[sgwilliams]

We are creating some bushings out of sintered bronze bar stock. We need to impregnate the bushings with oil so they will be self lubricating. The general practice as I have read is to immersing the bushings in SAE 30 motor oil heated to 150-175 degrees Fahrenheit in a vacuum. This is supposed to result in a 90% saturation of the bearing material. Our company has a vacuum furnace we use for carbuzing, tempering and hardening of our bearing material. We have never attempted this before as we usually purchase the bushings complete. This is a special order and doesn't use a standard bushing so we are making them ourselves.

My concern is out gassing of ingredients from the motor oil contaminating our expensive vacuum furnace and costing us downtime for cleaning. Also it's a concern for putting this in a vacuum and heating it at all. The flash point on the oil is 400 degrees Fahrenheit. But I have concerns with it foaming or doing some other weird stuff while in the vacuum. Does anyone have any experience with this or maybe some insight on how I should proceed?

 

[EdStainless]

I would strongly suggest that you build or buy a small vacuum chamber for doing this and DON'T do it in your furnace.
You will end up with oil residue everywhere.
You can do this with a small vacuum pump, a bell jar, and a hot plate.
If this is high volume then build a small system. It doesn't need high vacuum and it does need to be easy to clean.

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P.E. Metallurgy, Plymouth Tube

 

[chicopee]

Have you explored the possible use of leaded bronze alloys?

 

[sgwilliams]

We decided to NOT put this in the vacuum furnace and will just buy a small vacuum system with a heater attached to do process these. It's a very small investment and I have a feeling we will be doing many more of these products anyways so it justifies the cost. Thanks for the input EdStainless!

 

[sgwilliams]

Have you explored the possible use of leaded bronze alloys?

Yes we looked at this but the material specification is a requirement from the customer for SAE 841 Sintered Bronze w/ ND SAE 30 motor oil impregnation. This customer will not alter on their specification as they are design responsible we are just manufacturing the item for them.

 

[ornerynorsk]

Pre-preg bushing stock can be purchased. No need to go through the hassle and expense of doing the oil preg yourself.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[sgwilliams]

Pre-preg bushing stock can be purchased. No need to go through the hassle and expense of doing the oil preg yourself.

Luckily after discussing this with our purchasing department the material supplier had already sold us impregnated material, the material certification did not specify it was impregnated. the material item number did which was overlooked by myself and the other engineers. It's no longer an issue. The saturation is not as much as we would like but it will do for the order.

 

[sgwilliams]

To add to this post, i just wanted you all too know that there are small heated canister type vacuum systems available for around $350 that will accommodate this process. If you are interested let me know and I'll send you the vendor information.

 

[racookpe1978]

I can easily see the reason for heating the oil while it surrounds the material - the oil will flow into the bearing material much easier, much deeper. But why not under an inert atmosphere (nitrogen or even CO2) under high pressure? A vauum seems counter-intuitive to me, it seems to accelerate the oil to boil off, not soak in.

 

[sgwilliams]

I can easily see the reason for heating the oil while it surrounds the material - the oil will flow into the bearing material much easier, much deeper. But why not under an inert atmosphere (nitrogen or even CO2) under high pressure? A vauum seems counter-intuitive to me, it seems to accelerate the oil to boil off, not soak in.

I beleive, I may be wrong, that the vacuum is to suck the air from the material and it takes a while maybe 24 hours for all the air that will ever come out, to come out. then when the vacuum is released the empty space where the air was inthe material is filled instantly with the oil it is immersed in. The oil being heated it to make thinner so it will get pbetter penetration in the material.

 

[EdStainless]

That is it, you must remove the air or you will never fill it at any pressure.

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P.E. Metallurgy, Plymouth Tube

 

[tbuelna]

One issue with machining porous sintered bronze material is that metallic debris and smeared material from machining will be trapped within the surface pores. If contamination from metallic debris is a concern, the component can be chem etched after machining. But this would require the component to be impregnated with oil after chem etching.

I believe the oil impregnation process is done using a vacuum.