COATINGS

摘要

The invention relates to the provision of a hard surface coating on the cutting edge of a knife or other cutting implement and has for its objective to improve upon the process disclosed in co-pending EP Patent Application 93303062.9 which objective is met by a process for the production of a carbo-nitride coating comprising grinding one face of a V-shaped cutting edge of a knife blade or other cutting implement, locating the part-ground blank in a chamber provided with a means able to produce ions of a metal carbo-nitride, and subsequent to the coating process final grinding a second face of a V-shaped cutting edge, characterised by the blank being oriented such that the face to be coated is directed towards the cathode evacuating the chamber, impressing a current on a metallic element of the required metal to induce ion release, and to provide a required potential difference between the metallic element and the blank to cause ion bombardment of the blank at least over the area of the said ground face, said ion bombardment being controlled by the potential difference to induce heat in the blank to a level below the tempering temperature of the metal of the blank, releasing nitrogen and carbon-carrying gas, such as methane, into the chamber to apply a carbo-nitride coating to the face to be coated by physical vapour deposition at a temperature to cause the growth of columnar crystals, removing the blank from the chamber and grinding the second face of the V-shaped cutting edge to expose the carbo-nitride coating at the cutting tip of the cutting edge.