On ball milling, chromium powder reacted with the water used as the grinding medium The welding sandwiched the oxide films between the powder particles. For this . The iron is in the stainless steel picked up by the chromium powder.
A ball mill is a type of grinder used to grind and blend materials for use in mineral dressing . Some media, such as iron, may react with corrosive materials. to prevent oxidation or explosive reactions that could occur with ambient air inside