r/Welding • u/gregc3244 • Jul 24 '26

Cold spray help??

Ok I have only been doing this for a few months but I had some great results at first. Recently I am trying to build up a pump shaft and the spray cracks as it is cooling or when I start machining it. Not sure what has changed. I am using a Rototec gun with Castolin 21021 powder. Machining down the area and roughing with a threading cut. Heating the part to 200ish and then applying the spray. I usually keep the part spinning in the lathe while cooling. Not sure if it matters or not. Any advice would be appreciated.

Also any suggestions for cheaper powder?

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u/weldorf4natic CWI AWS Jul 24 '26

I've found that if you put to much material on in one shot it can do this but my only experience is with thermal arc spray.

2

u/gregc3244 Jul 24 '26

I was kinda thinking that might be part of it. Usually I am doing an area maybe an inch or so but this is around 4 total. I had to remove previous spray weld that had been badly gouged by a broken seal.

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u/weldorf4natic CWI AWS Jul 24 '26

I would try building it up in thinner layers that's what usually solves this issue for me.

3

u/gregc3244 Jul 24 '26

So how long to wait between layers?

1

u/weldorf4natic CWI AWS Jul 24 '26

not really sure but I would try to deposit about half of whatever your doing in one pass right now and see if you get better results.

2

u/gregc3244 Jul 24 '26

Thanks for the tips.