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Hard coating for cryogenic aluminum gear

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Hello,My name is Rick, I work as a mechanical designer/machinist in a University Physics Department. I am making 15" diameter aluminum gears for use in a cryogenic enviornment (vacuum and 4 degrees Kelvin). I would like some coating options to improve the strength and wear of the teeth. Something that will not outgass or flake off in use.
Teeth are 24 DP, 360 teeth,1/8" thickness. This will be a low torque, low rpm application.
Your assistance in this matter will be much appreciated. Thank you.

Rick Bihary
Research University Designer - Cleveland, Ohio

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I can think of two options at least for "normal temp ranges", but must confess I know little about operation at such low temperatures. One is hard anodizing. The other one would be electroless nickel plating either hardened or as plated.

Guillermo Marrufo
Monterrey, NL, Mexico

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4 Kelvin is incredibly cold. I think that the differences in the coefficients of thermal expansion is too great for hard anodize to work. I will question if EN will work for the same reason, especially in a vacuum. I think that you will probably have to go with titanium or stainless steel to work in that environment.
I would cold cycle it a couple of times before I used it as it very well might warp. Some things can be cryogenically hardened.

James Watts
- Navarre, Florida