We are examining 4340 steel parts (46 HRC) that have been shot peened and chromium plated. There appears to be particles imbedded into the steel under the chromium plating. This seems to be a surface condition. Is it possible to "push" some residual heat treating scale that did not clean up or some broken shot into surface of this material? Some of these particles are 0.0005" into the steel with chromium plating behind it or around it. The shot used was S-230 regular hardness. Your opinion please. Thanks.
