Smoothing the surface finish of rough metal articles

Abstract

A process for smoothing the surface of a manufactured metallic workpiece, the workpiece having a region having an initial roughness (Ra) of greater than 2.0 μm, the process involving (1) placing the metallic workpiece as the anode in an electrochemical cell, (2) arranging for the temperature of the electrolyte in the vicinity of the anode to be at least 50° C., (3) applying a voltage from 100V to 1000V across the electrochemical cell, thereby to generate a plasma membrane on the surface of the metallic workpiece which acts to remove material from the surface of the metallic workpiece, (4) maintaining the plasma membrane for a period effective to cause the roughness of the workpiece to be reduced.

1 . A process for smoothing a surface of a manufactured metallic workpiece, the workpiece having a region having an initial roughness (Ra) of greater than 2.0 μm, the process involving (1) placing the metallic workpiece as an anode in an electrochemical cell, (2) arranging for a temperature of an electrolyte in the vicinity of the anode to be at least 50° C., (3) applying a voltage from 100V to 1000V across the electrochemical cell, thereby to generate a plasma membrane on the surface of the metallic workpiece which acts to remove material from the surface of the metallic workpiece, and (4) maintaining the plasma membrane for a period effective to cause the roughness of the workpiece to be reduced. 
     
     
         2 . The process according to  claim 1 , wherein the initial roughness (Ra) of the workpiece is greater than 4.0 μm. 
     
     
         3 . The process according to  claim 1 , wherein a cathode surface area is 2 to 20 times greater than that of an anode surface area. 
     
     
         4 . The process according to  claim 1 , wherein the initial roughness (Ra) of the workpiece is less than 400 μm. 
     
     
         5 . The process according to  claim 1 , wherein the temperature of the electrolyte in the vicinity of the anode is from 50 to 100° C. 
     
     
         6 . The process according to  claim 1 , wherein the voltage applied across the electrochemical cell is from 150 to 700V. 
     
     
         7 . The process according to  claim 1 , carried out with a current density at the anode of 0.01 A/cm 2  to 1.00 A/cm 2 . 
     
     
         8 . The process according to  claim 1 , wherein a rate of material removal is from 1 to 12 μm/min. 
     
     
         9 . The process according to  claim 1 , wherein the plasma membrane is maintained for from 1 to 120 minutes. 
     
     
         10 . The process according to  claim 1 , wherein a pH of the electrolyte is from 3.0 to 12.0. 
     
     
         11 . The process according to  claim 1 , wherein an electrolyte solution concentration is from 1 wt/vol % to 25 wt/vol %. 
     
     
         12 . The process according to  claim 1 , wherein the workpiece has an initial roughness as a result of being manufactured by any one of the following methods: sand casting, investment casting, additive manufacturing, metal cutting (sawing, shaping, drilling, milling, turning), hot rolling, forging, flame cutting, and additive manufacturing.