ALUMINA-COATED CUTTING TOOL Russian patent published in 2018 - IPC B23B27/14 C23C16/40 C23C16/44 

FIELD: turning; drilling.

SUBSTANCE: invention relates to a coated cutting insert and to a method for its manufacture. Coated cutting insert, comprising a wear-resistant layer of α-Al₂O₃, consists of a substrate and a coating deposited thereon, consisting of one or more layers, including a wear-resistant layer of α-Al₂O₃, precipitated by chemical vapour deposition (CVD). Said coating has a total thickness of at most 60 mcm. Said wear resistant layer of α-Al₂O₃ has a thickness of 1–45 mcm, where in the micrograph obtained by scanning electron microscopy (SEM), the cross section of the layer of α-Al₂O₃ it contains at least two parts comprising a part with a first thickness and a part with a second thickness directly over the part with a first thickness. Part with first thickness has a columnar grain structure of α-Al₂O₃, and at the transition from the part of the first thickness to the part of the second thickness of the grain boundary, at least 1 of the 25 adjacent grains of α-Al₂O₃ have a changed direction, which is perpendicular to the grain boundaries in the part with the first thickness and is 90 ± 45 degrees. When making a coated cutting insert, the deposition of the part with the first thickness of the layer of α-Al₂O₃ is carried out in a CVD reaction chamber at a pressure in the range from 10 to 100 mbar, temperature in the range from 800 °C to 1050 °C for a time from 1 to 20 hours with a concentration of the reaction gases in the ranges from 2 % to 7.5 % CO₂, from 0.5 % to 5 % HCl, from 0.5 % to 5 % AlCl₃ and from 0.2 % to 1.1 % X. Deposition of said part with a second thickness of the layer of α-Al₂O₃ is carried out in a CVD reaction chamber at a pressure in the range from 100 to 300 mbar, temperature in the range from 800 °C to 1050 °C for a time from 5 minutes to 3 hours with a concentration of reaction gases in the ranges of more than 5 % CO₂, from 5 % to 25 % HCl, from 0.5 % to 3 % AlCl₃ and less than 0.35 % X, wherein X is selected from the group consisting of H₂S, SF₆ and SO₂ or combinations thereof.

EFFECT: providing a cutting insert with improved surface quality, reduced surface roughness and improved mechanical properties, specifically increased wear resistance of the rear surface and chipping resistance of the edges.

19 cl, 4 dwg, 8 ex