Method for mechanical surface treatment using electro-pulse assisted deep rolling

A mechanical surface treatment method for a metallic workpiece, the method comprising:

• using a first multi-axis (FMA) powered machine to impart motion to the metallic workpiece in a first FMA axis of motion;
• wherein the metallic workpiece includes a first layer of fused metallic powdered material;
• using a second multi-axis (SMA) powered machine to actuate a deep rolling tool relative to the metallic workpiece in a first SMA axis of motion, wherein the first SMA axis of motion is different from the first FMA axis of motion, wherein the deep rolling tool includes a roller, and the actuating of the deep roller tool includes applying the roller against the first layer with a first normal force sufficient to plastically deform the first layer;
• applying a first pulsed electrical current to the first layer concurrently with the application of the roller against the first layer, wherein the first pulsed electrical current is applied in a manner that produces an electroplastic effect at a surface of the first layer and a first near-surface region contiguous with the surface of the first layer, the electroplastic effect and the plastic deformation of the first layer producing a refinement in a grain structure of the first layer and an increase in dislocation sources and tangles within the grain structure of the first layer;
• subsequent to the application of the roller to the first layer of fused metallic powdered material, using an additive manufacturing process to produce a second layer of fused metallic powdered material disposed on the first layer of fused metallic powdered material;
• using the second multi-axis powered machine to actuate the deep rolling tool to apply the roller against the second layer with a second normal force sufficient to plastically deform the second layer;
• and
• applying a second pulsed electrical current to the second layer concurrently with the application of the roller against the second layer, wherein the second pulsed electrical current is applied in a manner that produces the electroplastic effect at a surface of the second layer and a second near-surface region contiguous with the surface of the second layer, the electroplastic effect and the plastic deformation of the second layer producing a refinement in a grain structure of the second layer and an increase in dislocation sources and tangles within the grain structure of the second layer.