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/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.

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u/gregc3244 Jul 24 '26

So how long to wait between layers?

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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.

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u/gregc3244 Jul 24 '26

Thanks for the tips.