Healing of surface defects in hard materials by thin coatings

Results on improvements in the transverse rupture strength of WC‐based cemented carbides, TiCN‐based cermets, and Al2O3‐based ceramics by the physical vapor deposition of thin coatings are presented. Evaluation of strength decreases in cemented carbides versus the length of half‐elliptic cracks in the near‐surface layer reveals enhancement of the cracks’ influence of the rupture stress value with decreasing fracture toughness of the cemented carbides. TiCN coatings obtained when simultaneous surface ion etching and depositing lead to healing Palmquist cracks formed near corners of Vickers indentations. The coatings are assumed to heal various defects present at the surface of hard materials, which result in an increase in transverse rupture strength of cemented carbides, cermets, and ceramics. Tool lifetime of Al2O3‐based ceramic cutting inserts can be improved by depositing the coatings due to the healing surface defects resulting in retardation of cracks’ initiation and propagation in interrupted cutting.Results on improvements in the transverse rupture strength of WC‐based cemented carbides, TiCN‐based cermets, and Al2O3‐based ceramics by the physical vapor deposition of thin coatings are presented. Evaluation of strength decreases in cemented carbides versus the length of half‐elliptic cracks in the near‐surface layer reveals enhancement of the cracks’ influence of the rupture stress value with decreasing fracture toughness of the cemented carbides. TiCN coatings obtained when simultaneous surface ion etching and depositing lead to healing Palmquist cracks formed near corners of Vickers indentations. The coatings are assumed to heal various defects present at the surface of hard materials, which result in an increase in transverse rupture strength of cemented carbides, cermets, and ceramics. Tool lifetime of Al2O3‐based ceramic cutting inserts can be improved by depositing the coatings due to the healing surface defects resulting in retardation of cracks’ initiation and propagation in interrupted cutting.