Copper Coating on Slip Ring

[Stephen Booth]

we received this inquiry for repairing slip rings.

Diameter is 300 mm and worn out to 299 mm so about 0.5 mm build up.

The issue so far is that the substrate is oxygen free copper.  Any suggestions on how to build up using:

a) Arc Spray
b) HVOF
c) GTAW
d) PTAW

I assume the coating must be oxygen free as well.....

[Vadim Verlotski]

Hi Stephen,
unlike steel parts, hardfacing methods are rarely used on copper parts. This is due to the high thermal conductivity of copper, which greatly hinders the surfacing processes. But copper substrates are very good for all thermal spraying methods, both for high-speed (cold spraying, HVOF, HVAF, detonation spraying and high-velocity plasma spraying) and for "slow" spraying methods (flame spraying, traditional plasma spraying and arc spraying) .
Almost any coating perfectly adheres to copper on one condition: the copper surface should not oxidize during the spraying process. This condition is met by providing a low temperature of the part (good cooling at a long distance of deposition) and/or by using the reduction flame of plasma torches (short distance of deposition).

[Stephen Booth]

Hi Stephen,
unlike steel parts, hardfacing methods are rarely used on copper parts. This is due to the high thermal conductivity of copper, which greatly hinders the surfacing processes. But copper substrates are very good for all thermal spraying methods, both for high-speed (cold spraying, HVOF, HVAF, detonation spraying and high-velocity plasma spraying) and for "slow" spraying methods (flame spraying, traditional plasma spraying and arc spraying) .
Almost any coating perfectly adheres to copper on one condition: the copper surface should not oxidize during the spraying process. This condition is met by providing a low temperature of the part (good cooling at a long distance of deposition) and/or by using the reduction flame of plasma torches (short distance of deposition).

Hi Vadim 
thank you very much for the input.  Really appreciate it.

We will let you know how it goes if we get the job....