DIAMOND DEPOSITION ONTO WC-6-PERCENT-CO CUTTING-TOOL MATERIAL - COATING STRUCTURE AND INTERFACIAL BOND STRENGTH

Diamond coatings were grown on WC-6%Co cutting tool material. Measurem ents were carried out to investigate the effects of diamond seeding of the substrate before deposition, removal of cobalt from the substrate before deposition, and boron incorporation into the coating during gr owth on the growth rate, morphology and structure of the coating, and coating-substrate adhesion. Diamond seeding of the substrate resulted in a higher growth rate and diamond fraction of the coating relative t o a polished and unseeded surface. Etching of cobalt from the substrat e resulted in a higher growth rate, diamond fraction and adhesion stre ngth relative to the unetched surface. Introduction of methanol into t he gas phase led to a lower growth rate, diamond fraction and adhesion strength relative to the case when no methanol was injected. Introduc tion of boron oxide (B2O3) along with methanol into the gas phase did not affect the growth rate but increased both the diamond fraction and adhesion strength relative to the case when only methanol was added. It is believed that adhesion failure occurs at the diamond-substrate i nterface, possibly within a soft nanocrystalline graphite transition l ayer. (C) 1997 Published by Elsevier Science S.A.