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binding Au to stainless steel

binding Au to stainless steel

binding Au to stainless steel

(OP)
I am looking for a method to bind high purity (99.999) Au foil to a stainless steel substrate. We have tried the brute force method of scoring the stainless steel surface and pressing the Au, but this leaves the Au surface very rough (due to the roughened stainless steel surface).  I am wondering whether it is possible for Au to form an alloy with stainless steel directly or by using an intermediate soldier. Ideally this would be done with relatively low T (< 260 C). Any advice is appreciated.

RE: binding Au to stainless steel

Why not just electroplate?

RE: binding Au to stainless steel

Would glue be acceptable?
You can solder.  I would start by plating the stainless with Cu or Ni and then looking for a solder to use.

What shape are you working with?  If you are working with strips of metal you could roughen the stainless (blast and piclkle) and the roll bond them.  If the finish roll is polished you will get a good finish on the gold.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: binding Au to stainless steel

(OP)
I should explain that we are making sample mounts for electron microscopy and mass spectrometry analysis. The Au needs to be  high purity (99.999) - is this possible by electroplating?

Another requirement is that the binding agent is conductive, so glue is not acceptable.

The stainless steel substrates are 1 cm disks that are a few mm thick.  The gold is 0.003"-thick foil cut into 0.1" wide squares. We us a sapphire plate to press the Au into the substrate.

RE: binding Au to stainless steel

I read somewhere, some years ago (say 10+) of a technique called "explosive bonding" where Al sheet was "joined" to a parent metal by holding/clamping the two pieces slightly apart over a container. An explosive charge in the container forced the Al to close bond with the parent metal. I don't know what became of the method but its just a suggestion you might explore, try a web search.

RE: binding Au to stainless steel

Sputter coating?

it might take a long time to build up .003" but it would be clean.

Nick
I love materials science!

RE: binding Au to stainless steel

Yes, a good plater, using clean fresh solutions and careful control of cleanliness (both parts and tanks/equipment) can achieve very high purity of deposited gold; but then we were satisfied at 2- or 3-9's purity for the optical properties.  As Ed said, a typical process starts with a copper "strike" layer, followed by nickel, then gold plating.  This is to ensure a good metallurgical bond (no blistering).  The same sequence of layers may help in trying to form a diffusion (mechanical) bond using foil.

RE: binding Au to stainless steel

Platting will not be pure enough vor you.  I tried it on sample holders for an X-Ray spectrometer.
You could gold plate and then mechanically bond.  Work with 1/2" wide strips a foot long or so.  Find a small rolling mill in a lab to use for the bonding.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: binding Au to stainless steel

Ed is right about electroplated gold purity -- the highest commercially available, for the semiconductor industry, is 99.95%.

I suggest polishing the SS strip, electroplating with nickel (no copper, just a Wood's nickel strike), then roll bonding followed by baking to improve adhesion.

Does the Au foil really need to be 0.003" thick?
If not, just gold coat the Ni-plated SS by evaporation.

RE: binding Au to stainless steel

What about glue with metal filler so that it is conductive?

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