We subcontract most of our peening needs and recently received an order of parts from one of our suppliers.

We noticed severe surface irregularities that did not look like a typical shotpeened surface. The material is aluminum, peened to a propietary spec similar to AMS-2430, 8-12A, cast steel shot, 100% coverage. The material, as shown in the pictures, looks almost as though it "flowed" in a certain direction similar to what you would expect if it was melted and resolidified. I am looking for any insight as to what may have caused this. My initial guess is far to great of an intensity in these areas. I also would like to better understand how this could have happened in one area but not on another even though the parts are somewhat symmetrical.

I know that you do not know the shotpeeners exact process, but any guidance would be appreciated.

Thanks.

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I suggest you visit your supplier and ask to review their process plans and then witness a typical peening cycle. I suspect that excessive coverage may be the dominant contributor to the surface texture exhibited in your photos but the intensity might also be at fault.

You state that the material is aluminium but is surely an aluminium alloy. The surface flow characteristics are consistent with an excessive amount of shot (having too high an intensity) being fired at an angle to the component's surface using a wheel-blast machine. A stated "100% coverage" is difficult to either monitor or control. Suggest lowering both peening intensity and coverage together with trying to have shot impact nearer to 90 degrees to the surface.