A METHOD OF IMPROVING SURFACE HARDNESS, WEAR RESISTANCE OR FATIGUE STRENGTH OF A COBALT-CHROMIUM BASED ALLOY MEDICAL IMPLANT WITHOUT LOSS OF CORROSION RESISTANCE AND A SURFACE-HARDENED COBALT-CHROMIUM BASED ALLOY MEDICAL IMPLANT PRODUCIBLE BY THE METHOD

摘要

The present invention relates to a method of modifying a surface characteristic (e.g., wear resistance and/or corrosion resistance) of a cobalt-chromium based alloy article. The method comprises plasma treating the article at a temperature in the range of from 300° C. to 700° C. and at a pressure of from 100 Pa to 1500 Pa for 1 hour to 50 hours in an atmosphere comprising at least one carbon-containing gas, whereby to introduce carbon into a surface region of said article. The present invention also resides in a surface-hardened cobalt-chromium based article producible by the method of the invention. The article is characterised by having a surface region comprising a supersaturated solid solution of carbon in cobalt or a surface region comprising a supersaturated solid solution of carbon in cobalt and chromium carbides. Surface hardened articles producible by the method of the invention include medical implants and engineering components.