A New Hybrid Process for Surface Modification by combining Brush Plating with Nitrocarburizing

摘要

In the past, electroplated hard chromium coatings have been very widely used to improve the corrosion and wear resistance of machine parts. Because of the cost and hazard issues associated with the Cr plating process, coatings based on a number of Ni-based alloys (e.g., Ni-W) have been proposed as replacements for Cr electroplate.~((1,2,3)) However, these proposed replacement technologies have not been generally successful in improving wear resistance because of their low hardness.For example, brush-plated Ni-W has a hardness of 495 VHN, which compares with 819 VHN for tank-plated hexavalent Cr.~((4)) Conversely, it has been suggested that a coating based on a metal-matrix composite with ceramic particles as reinforcement phases should exhibit much better wear resistance.~((1,5)) The wear resistance of a Ni-Co-ZrO_2 composite coating was shown to be 1.81 times greater than that of an unreinforced Ni-Co coating because the ZrO_2 particles readily bear the operating load and the Ni-Co matrix acts to hold the particles in place.~((6))