Strengthening of hard materials by depositing thin coatings

摘要

Results on improvements in the transverse rupture strength, toughness and performance of low-cobalt grades of WC-Co hardmetals, TiCN-Ni-MO cermets, Al_2O_3 and Al_2O_3-TiC cutting cermaics by depositing thin coatings are presented. Physical vapour deoposition, chemical vapour deposition, evaporation-and-condensation and metal organic chemical vapour deposition techniques have been employed for strengthening of the hard materials. Limitations and advantages of these techniques from the viewpoint of strengthening and toughening of various substrate materials are discussed. Retardation or complete elimination of Palmquist cracks during Vickers indentation of such a brittle material as pure alumian are shown to be possible by use of a suitable coating and deposition technique. The deposited thin coatings are assumed to heal various surface defects present at the surface of hard materials, which results in an up to 35