Method for forming a chromium carbide layer on the surface of an iron, ferrous alloy or cemented carbide article

Claim 1

IN A METHOD FOR FORMING A CHROMIUM CARBIDE LAYER ON THE SURFACE OF AN IRON, FERROUS ALLOY OR SINTERED TUNGSTEN CARBIDE CONTAINING COBALT ARTICLE, THE SURFACES OF WHICH ARTICLES CONTAIN AT LEAST 0.06 PERCENT BY WEIGHT OF CARBON, WHICH COMPRISES PREPARING A MOLTEN BATH CONTAINING ESSENTIALLY OF BORIC ACID OR A BORATE AND METALLIC CHROMIUM DISSOLVED THEREIN, IMMERSING SAID ARTICLE INTO SAID MOLTEN TREATING BATH, MAINTAINING SAID ARTICLE IN SAID MOLTEN TREATING BATH TO FORM THE CHROMIUM CARBIDE LAYER ON THE SURFACE OF SAID ARTICLE, AND REMOVING SAID ARTICLE FROM SAID MOLTEN TREATING BATH, THE IMPROVEMENT WHEREIN SAID MOLTEN TREATING BATH IS PRE PARED BY THE METHOD WHICH COMPRISES, HEATING A BORIC ACID OR A BORATE SELECTED FROM THE GROUP CONSISTING OF SODIUM BORATE AND POTASSIUM BORATE TO ITS MOLTEN STATE TO FORM A MOLTEN BATH, DIPPING A METAL BLOCK OF CHROMIUM OR A CHROMIUM ALLOY CONTAINING NOT GREATER THAN 10 PERCENT BY WEIGHT OF TI, ZR, HF, MN, SI, A1, MG, CA OR THE RARE EARTH ELEMENTS WHICH REDUCE BORIC ACID OR BORATE TO METALLIC FORM INTO THE MOLTEN BATH AND APPLYING AN ELECTRIC CURRENT TO THE MOLTEN BATH THROUGH SAID METAL BLOCK AS ANODE AND AN ELECTRIC CONDUCTIVE MATERIAL, WHICH IS IN CONTACT WITH THE MOLTEN BATH, AS CATHODE TO ANODICALLY DISSOLVE SAID METAL BLOCK.